Reduced false recognition in amnesia could be a result of impaired by mikesanye

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									Reduced false recognition in amnesia could be a result of impaired item-specific

  memory: the relationship between item-specific memory and gist memory.




                                  Jack Nissan

                        Supervisor: Sharon Abrahams
Abstract

It is a common finding that amnesic patients produce fewer false recognitions than

healthy controls, and this has led to assumptions that gist memory is damaged in these

patients (Schacter et al., 1996, Budson et al., 2000). Two experiments used false

recognition paradigms to ascertain whether this result could instead be a consequence

of impaired item-specific memory. Experiment 1 aimed to reduce the item-specific

memory of healthy adults to reflect that of an amnesic patient, by using an articulatory

suppression task, while Experiment 2 aimed to increase the item-specific memory of

amnesic patient JY to reflect that of a healthy adult, by bringing her to criterion on the

relevant study-lists. Results indicated that when item-specific memory was

sufficiently reduced in healthy adults, they produced a similar pattern of results to that

found in amnesic patients, and when JY’s item-specific memory was increased, she

produced a similar pattern of results to healthy adults. This suggests that the previous

assumption that gist memory is damaged in amnesic patients might be flawed. The

implications of this are discussed in terms of the relationship between item-specific

memory and gist memory.




                                            2
Introduction

Amnesic disorders can cause profound disruptions to people’s lives, both in terms of

one’s general wellbeing and also with regard to one’s ability to live independently. It

is thus important to find effective ways to treat and/or cope with these problems, and

crucial to this is an accurate understanding of the specific disorder and precisely

which areas of memory it affects.



There is comprehensive evidence that amnesic patients show substantial deficits in

episodic memory. Episodic memory is the ability to remember certain events,

episodes or information within a particular temporal or spatial context, and patients

perform consistently badly on tasks which assess this, such as recalling stories,

sentences and individual words, and recognising words, pictures and faces (Nebes,

1992). Two subdivisions of episodic memory have been described as item-specific

memory (Balota et al., 1999; Budson et al., 2000) and source monitoring ability (for a

review, see Johnson et al., 1993). Item specific memory is the ability to remember

individual items in themselves, without putting them into any semantic context. It can

be tested using some of the methods described above, such as recall of unrelated

words, pictures and faces, and as mentioned, amnesic patients are severely impaired

in their ability to perform these tasks. Source monitoring is the ability to identify and

memorise the source of information or the context in which it was learnt. It is

inherently related to, and in a sense included in, item-specific memory, as one needs

to be able to remember the origin of specific information in order to recall it

appropriately. For example, in order to accurately recall a list of words, one needs to

be able to distinguish between the words that were on the particular list from any

other words that might come to mind from different sources. In real-life situations,



                                            3
source monitoring allows us to form opinions and judgements, as to do so we need to

discriminate between various sources of information, and it also enables us to

distinguish what is real from what is imagined (Johnson et al, 1993). Numerous

studies have found source memory deficits in amnesic patients (eg. Schacter et al,

1984; Multhaup and Balota, 1997; Dalla Barba et al., 1999; Smith and Knight, 2002;

Pierce et al., 2005). For example Multhaup and Balota (1997) found that Alzheimer’s

disease (AD) patients struggled to distinguish between information they had read and

information generated by themselves, and Dalla Barba et al. (1999) found AD patients

were impaired in their ability to discriminate between objects they had seen and

imagined.



While it is widely accepted that amnesic syndromes are extremely damaging to the

various elements in episodic memory, their effect on semantic memory is more

controversial. Semantic memory refers to the general meaning of information. It is a

memory for information within a semantic context as opposed to a temporal or spatial

context, as is the case with episodic memory. Tulving (1972, p386) describes it as a

“mental thesaurus, organised knowledge a person possesses about words and other

verbal symbols, their meaning and referents, about relations among them and about

rules, formulas, and algorithms for the manipulation of the symbols, concepts and

relations”. So whereas episodic memory might allow a person to recall that he walked

passed a cinema yesterday, or that he saw the word cinema written on a memory test,

semantic memory is responsible for a general understanding of what a cinema is: that

it relates to films, a big screen, going out etc. Several studies report that amnesic

patients show deficits on various semantic memory tasks, such as category fluency

tasks (Troster et al, 1989) and freely producing associations to words (Gollan et al.,



                                            4
2006). However, other researchers have argued that these particular tasks require

large attentional demands and that the deficits observed are actually the result of

damage to an attentional control system and do not necessarily reflect any damage to

the patients’ semantic memory (Balota et al., 1999, Watson et al., 2001). Various

studies report that AD patients are deficient in attentional and inhibitory processes

(Spieler et al., 1996; Faust et al., 1997, Simone and Baylis, 1997a, 1997b), and

evidence that their semantic memory is actually in tact comes from certain semantic

priming tasks, whereby patients demonstrate in tact priming effects under conditions

that do not reflect attentional processes (eg. Balota and Duchek, 1991), but disrupted

priming effects under conditions that do. (eg. Ober and Shenaut, 1995). The literature

on semantic memory in amnesia is thus divided and the key debate is about whether

amnesic syndromes damage semantic memory itself or whether they damage other

functions which interfere with the access to semantic memory.



Another area of memory that forms a part of semantic memory is known as gist

memory (Reyna & Brainerd, 1995). This is the ability to put information into a larger

semantic context. It allows us to obtain an understanding of the general meaning of

information and get the gist of what it is about. Gist memory has been explored

extensively through studies on false memories, as the two seem to be related. This

has been demonstrated in a series of experiments that asked healthy participants to

study semantically related word lists, which converged on certain target words,

sometimes called critical lures (these were not presented to the subject in the study

list). For example, one list from an experimental paradigm called the DRM (Roediger

and McDermott, 1995) contains the words: HOT, SNOW, WARM, WINTER, ICE,

WET, FRIGID, CHILLY, HEAT, WEATHER, FREEZE, AIR, SHIVER, ARCTIC,



                                            5
and FROST, and the critical lure for this list is COLD. After studying several of these

lists, participants completed a recall or recognition phase, and results have shown that

healthy adults consistently recalled or recognised the critical lures that were not on the

original lists (Underwood, 1965; Cermak, 1973; Roediger and McDermott, 1995;

Norman and Schacter, 1997). The fact that healthy participants produce these lures

has been attributed to their gist memory. The theory is that through seeing the list of

related words, a memory for the general gist of the list is formed, which encompasses

representations of both the words on the actual lists and any others which are related

to the gist, such as the critical lures. Hence when asked if a critical lure was on the

list, participants falsely respond “yes”, as they are using their gist memory to identify

the word.



These experiments using related word lists have been modified and extended to study

patterns of false recognition across different groups, and these patterns have revealed

some interesting findings about memory and how different aspects of memory interact

with each other. For instance, when false recognitions are compared between healthy

young and old adults, it is found that old adults falsely recognise more critical lures

than young adults (Schacter, Koustaal et al., 1997; Balota et al., 1999; Norman and

Schacter, 1997). In one way this result might seem surprising, as it could imply that

old adults have a better gist memory than young adults, but further experiments reveal

this is not the case. Dehon and Bredart (2004) carried out an experiment to assess

false recognitions in young and old adults but added an extra phase where participants

had to report any other words that came to mind during the experiment. They found

that young and old adults reported the same number of related lures but that young

adults tended to think of them in the learning stage while old adults produced them in



                                            6
the recall phase. This implies that there is no difference in the gisting processes in

young and old adults, since they thought of the same number of related lures, and that

the difference in false recall relates more to source monitoring ability. Other

experiments have demonstrated an age difference in source monitoring (eg. Tun et al.,

1998; McIntyre and Craik, 1987; Dywan and Jacoby, 1990), and this could therefore

be one reason behind the age difference in performance on false recognition tasks.

Another explanation focuses on the interaction between item-specific memory and

gist memory (Kensinger and Schacter, 1999; Balota, 1999; Budson et al., 2000).

Remembering related word lists is likely to involve both these processes, where gist

memory assists in the recognition of all related words (both studied and unstudied),

and item-specific memory enables us to remember the individual words in

themselves, and hence exclude any unstudied related words that our gist memory

might endorse. As young adults have a better item-specific memory than old adults,

they are more able to use this information to regulate their gist memory, and hence

they produce less false recognitions than old adults. Support for this theory comes

from an experiment by Kensinger and Schacter (1999) in which the entire study-test

procedure was repeated across five trials. Results indicate that young adults are able

to use this repetition to reduce the number of false recognitions, whereas older adults

cannot, and it is suggested that this is due to an increasing item-specific memory in

the younger adults.



When false recognitions are studied in people suffering from amnesic disorders, the

results are quite surprising. Given that both their source memory and item-specific

memory is so poor, we might expect these patients to show an even greater increase in

the number of lures they falsely recognise. However, the results indicate the complete



                                            7
opposite, finding that they falsely recognise even less related lures than healthy young

adults (eg. Budson et al., 2000; Budson, Desikan et al., 2001). A large body of

literature explains this result by inferring that amnesic patients have an impaired gist

memory (eg. Budson et al, 2000; Budson, Desikan et al., 2001; Budson et al., 2006;

Gallo, 2006). This certainly seems like a rational explanation, but there may be

another way of looking at the results that would lead to a different conclusion. It

could be that in order to gist, we need a certain amount of information to gist from.

Whilst it may not have been tested, it seems common-sense that we would get a

clearer gist from a list of twenty related items than we would from a list of two.

Hence an increased item-specific memory, whilst being able to oppose gist memory in

one sense, might at the same time enhance it, since the more items one has available

to them, the better their gisting resources. Further to this, there might be a sort of

threshold, whereby one cannot gist effectively if there are not enough items available

to them. This would not imply that their ability to gist is damaged, just that there is

simply not enough information for it to act on, and it is possible that this is the case

with amnesic patients. In a similar repeated trials experiment to the one described

above (Kensinger and Schacter, 1999), Budson et al (2000) found that false

recognition in AD patients actually increased over trials, in sharp contrast with young

adults whose false recognition decreased (due to an improved memory for specific

items) and old adults whose false recognition remained fairly stable. While the

authors explained this result in terms of an impaired gist memory in AD patients that

improves with repetition, it could instead be the AD patients’ impaired item-specific

memory that improves, which in turn enables their intact gist memory to come into

play. However, unlike healthy adults, they may still be unable to remember enough

specific items to suppress the gist representations now available to them.



                                             8
Some evidence that gist memory might be in tact in amnesic patients comes from

studies conducted by Balota and colleagues (Balota et al, 1999; Watson et al 2001),

which analyse the number of false recognitions of related lures with respect to the

number of true recognitions of studied items. They matched AD patients who

performed well on true recall with healthy older adults who performed poorly on this

measure, and found that under these conditions AD patients actually showed a higher

rate of false recognition than the older adults. This seems to imply that the reduced

number of false recognitions found in AD patients is more a result of poor item-

specific memory than of a damaged gist memory. Another observation that raises

questions about the use of false recognition results to infer a damaged gist memory in

amnesic patients, is the fact that this reduction in false recognitions has been found in

patients suffering a variety of amnesias and amnesic syndromes, such as Korsakoff’s

syndrome (Schacter et al., 1996; Schacter, Verfaille et al.,1997; Koustaal et al., 2001),

semantic dementure (Simons et al., 2005), Alzheimer’s disease (Budson et al, 2000;

2006), frontal lobe lesions (Verfaille et al., 2004) medial temporal lobe lesions

(Verfaille et al., 2004), and from mixed etiologies including anoxia and encephalitis

(Schacter et al., 1996; Koustaal et al., 2001, Verfaille et al., 2002). These disorders

all affect different areas of the brain, so it seems unlikely that they all damage the

same function. However, it is more feasible that gist memory, as a particular memory

function, could be accessed in various ways, and thus it seems more likely that each

disorder prevents access to this function in some way as opposed to damaging it

directly.




                                            9
Hence, in a similar way that the results of certain semantic memory tasks might imply

either damage to semantic memory itself or an inability to access it, the false

recognition results of amnesic patients could imply either damage to their gist

memory itself or an inability to access it, perhaps due to the poor item-specific

memory caused by the amnesia. The current experiment tests for the possibility that

the patterns of false recognition observed amnesic patients are more a product of a

weak item-specific memory than of a damaged gist memory. Experiment 1 requires

healthy young and old adults to perform two false recognition paradigms, one of

which involves carrying out an articulatory suppression task during the presentation

of the word lists. The purpose of the articulatory suppression task is to prevent

participants from rehearsing the words and hence to reduce their item-specific

memory so that it reflects that of an amnesiac. Since the participants are healthy and

their gist memory is in tact, if they produce less false recognitions under the

articulatory suppression condition, this would mimic the pattern observed in amnesic

patients and thus suggest that this pattern does not necessarily reflect a damaged gist

memory, but could instead be the result of an impaired item-specific memory.

Experiment 2 is a case study on amnesic patient JY. Again there are two false

recognition paradigms to be completed, and in one of these the intention is to increase

the item-specific memory of JY to mimic that of a healthy adult, by bringing her to

criterion on the various lists. If, after being brought to criterion, JY produces more

false recognitions than in the control condition, this would again suggest that it is a

damaged item-specific memory as opposed to a damaged gist memory that causes the

observed reduction in false recognitions in amnesic patients.




                                            10
Experiment 1

Previous literature has shown that patients with various amnesic syndromes produce

less false recognitions than healthy young and old adults (eg. Schacter et al., 1996;

Budson, 2000), and these results have been used to conclude that this is due to a

damaged gist memory in the amnesic groups (eg. Schacter et al., 1996; Budson et al.,

2000, Gallo et al., 2006). However, when false recognition results are analysed with

respect to veridical memory the opposite effect is found, and patients show an

increase in false recognitions (Balota et al., 1999; Watson et al., 2001). This fits with

literature on semantic memory in AD that suggests it is access to semantic memory,

rather than semantic memory itself, that is damaged (Balota and Duchek, 1991; Balota

et al., 1999; Watson et al., 2001). Hence, the theory posited by this paper is that the

reduced number of false recognitions observed in these patient populations does not

reflect a damaged gist memory but rather an inability to access it. Access to gist

memory might require a certain level of item-specific memory and since these

patients’ item-specific memory is so poor, it may be below the required level for them

to gist effectively.



This experiment compares performance of healthy young and old adults on two false

recognition paradigms. One of these is a control condition, and the other involves

participants performing an articulatory suppression task whilst studying the word lists.

The articulatory suppression task aims to reduce the participants’ item-specific

memory to reflect that of an amnesiac. Since it is hypothesised that this level of item-

specific memory is too low to gist effectively, it is predicted that subjects will produce

less false recognitions under the articulatory suppression condition than under the

control condition. However, in the control condition, the level of item-specific



                                           11
memory in both young and old adults is high enough to gist effectively, and it is thus

predicted that young adults will produce less false recognitions than old adults, since

they should be able to use their better item-specific memory to regulate their gist

memory more so than old adults.



Method:

Participants:

Four subjects were excluded from the analysis as they did not complete the

experiment appropriately. Of the participants included in the analysis, younger adults

were 32 students (16 male, 16 female) from Edinburgh University, all aged between

18 and 25 years old (mean=21.59, SD=1.48). Older adults were 33 residents (11

male, 22 female) from Edinburgh or nearby. They were all aged between 60 and 75

(mean=68.30, SD=4.00) and were recruited partly through a departmental volunteer

list and partly through advertising around the city in garden bowls clubs, charity shops

and churches.



Materials and tasks:

False recognition task: There were two false recognition paradigms (A and B) in

total and both were presented on a computer. Each paradigm consisted of twelve

related word lists, and each list contained fifteen related words, which were presented

in the study phase, and an associated critical lure which was presented in the

recognition phase. The lists were taken from an experiment by Bellamy and Shillcock

(2007), and were mostly the same as those used in a well recognised false recognition

paradigm called the DRM (Roediger and McDermott, 1995), though some words

were adapted to better suit the native language of British English as opposed to



                                           12
American English (see appendix A for a table of all the lists used and the respective

critical lures). The words from each list were displayed one at a time at the centre of

a computer screen for a duration of two seconds per word. There was a one second

pause between each word during which the participants focused on a fixation cross in

the centre of the screen. After each list, written instructions appeared informing

participants that they had to complete some simple maths problems. The maths

problems were then displayed and participants had to type in the answer and hit

“enter”, after which another problem would be presented. After thirty seconds, a

message appeared on the screen saying “well done” and the next list of words was

displayed. After all twelve lists had been displayed, there was a recognition phase.

Instructions appeared on the screen informing participants that random words would

appear and that they had to decide whether or not these words were on any of the lists

they had just seen. If they thought the word was on any of the lists, they had to hit the

“yes” key and if they thought the word was not on any the lists they had to hit the

“no” key (the actual keys were on a standard computer keyboard but were covered

with “yes” and “no” stickers). In order to avoid any right- or left-handed bias, they

were told to use only the index finger of their preferred hand to press both “yes” and

“no”. There were 48 words in total in the recognition phase and these consisted of the

12 critical lures, 24 studied words (two from each list) and 12 completely unrelated

words that were neither on or related to any of the lists. The computer programme

recorded the results of the recognition phase.



Free recall task: Two lists were used for each participant and both consisted of

unrelated words (see appendix B for a table of these lists). The function of these lists

was to gain an independent measure of item-specific memory. Each word was printed



                                           13
on an A5 sized flashcard. All words were taken from “Birkbeck Word Association

Norms” (Moss and Older, 1996) and this book was used to ensure that the words were

as semantically unrelated as possible, and also that neither of the lists would be

subject to semantic interference with each other or any of the lists used in the false

recognition paradigm. In each list, the most common 10 associates of every word

were cross-referenced with each other and all the words in the false recognition

paradigms to ensure they were completely unrelated. If any word or associated word

was on any of the lists in the false recognition paradigms or on any of the free recall

lists then that word was discarded. The lists were also equally split between concrete

and abstract words to try and replicate the difficulty of the lists in the false recognition

paradigm. For each of the recall lists, participants were instructed to try to remember

as many words as possible. The list was then presented, one word at a time and a rate

of approximately 2 per second. After the last word was presented, participants were

asked to count down in intervals of three from a number above 200, and after thirty

seconds of doing so, they were told to recall as many of the words as possible in any

order. The number of words correctly recalled was recorded on a score sheet.



Articulatory suppression task: Throughout one of the unrelated free recall tests and

one of the false recognition paradigms, participants had to perform an articulatory

suppression task while they studied the words. The task was the same as that used by

Beaman and Jones (1997), and involved saying the letters A-G repeatedly at a rate of

approximately 2 letters per second. Participants were instructed to keep the flow of

letters as constant and regular as possible and to avoid leaving a pause between the G

and following A. The articulatory suppression task was only performed whilst




                                            14
studying the word lists and not throughout the recall or recognition phases or during

the maths problems.




National Adult Reading Test - Revised (NART) (Nelson and Willison, 1991): The

NART was used to match the young and old groups by a general measure of

intelligence, so as to ensure that any effect of age would not be due to a difference in

IQ. The test itself is a list of words which participants have to read out loud. The

marking is based on the pronunciation of the words and participants are thus

instructed to attempt to pronounce all of the words, even if they do not recognise

them.



Procedure:

Participants were told that most of the experiment would take place on the computer

and that in addition there would be a few tests carried out in person. The general

procedure for the false recognition tests, free-recall tests and articulatory suppression

task was described to participants and they were asked to sign a consent form.

Participants first carried out one of the free recall tasks, and this was followed by one

of the false recognition tests. They then had a five minute break, after which they

completed the other free recall task, followed by the remaining false recognition test.

Throughout one of the unrelated free recall tasks and one of the false recognition

tests, participants had to carry out the articulatory suppression task whilst studying the

words. They were instructed to perform the articulatory suppression only throughout

the presentation of the words and not during the maths problems or throughout the

recall or recognition phases. The order that the false recognition, free recall, and

articulatory suppression tasks were performed was varied equally between


                                            15
participants to control for any effect of test order. After the second false recongition

task had been completed, participants carried out the NART.



Results:

First, a word must be said about correction procedures that are frequently used in

analysing false recognition paradigms such as this one. These are carried out on

critical lures and studied words to account for biases in the results. There are two

principal methods that have been employed in previous studies. The most common

method involves subtracting the proportion of “false alarms” (falsely recognised

unrelated words) from the proportion of “hits” for critical lures (falsely recognised

critical lures) and studied words (correctly recognised studied words). So for each

participant, the corrected score for critical lures would be the proportion of falsely

recognised unrelated words subtracted from the proportion of falsely recognised

critical lures, and the corrected score for studied words would be the proportion of

falsely recognised unrelated words subtracted from the proportion of correctly

recognised studied words. The other method is signal detection analysis (see Banks,

1970 for a review), in which the corrected scores for critical lures and studied words

are obtained by entering the proportions of false alarms and hits into certain

equations. Given that these experiments aim to assess one’s ability to gist by looking

at false recognitions of critical lures, there is a potential problem with the first

correction procedure in its assessment of critical lures. While it accounts for

recognition errors of unrelated words, it does not seem to account for errors made in

the recognition of studied words. Recognition of studied words involves a

combination of item-specific and gist memory (Budson, 2000), since the studied

words all come from semantically related lists. Hence failing to recognise these



                                             16
words should be a sign of an impaired gist memory, in the same way that failing to

recognise critical lures is taken as a sign of an impaired gist memory. This should

therefore be taken into account when analysing critical lures. Signal detection

analysis uses a more independent methodology to correct for biases and is a widely

accepted and acclaimed procedure. As a result, a signal detection analysis of the data

from the current experiment is presented in this paper. However, the data was also

analysed using the standard correction procedure and the main differences are

mentioned at the end of the results section. The type of signal detection analysis used

in the current study was a simplified version of d’, the equation for which is

A’ = 0.5 + [(H - FA)(1 + H - FA)] / [4H(1 - FA)] (Radvansky, 2006). This method

will be referred to from here on as the A’ correction procedure, and any critical lure

scores or studied word scores corrected by this method will be referred to as A’

critical lures or A’ studied words respectively.



Table 1 shows the means and standard deviations for the percentages of A’ critical

lures, A’ studied words and unrelated words endorsed in the young and old adult

groups and within each experimental condition.



                                   Control                Articulatory suppression (AS)
                         A'          A'                      A'          A'
                       Critical   Studied     Unrelated    Critical   Studied     Unrelated
                        lures      words       words        lures      words       words
            mean        85.58      89.03        6.78        86.63      85.72        10.42
Young        SD         9.88        7.28        9.57        8.77       8.20         11.20
            mean        89.11      89.72        9.09        86.17      86.23        15.15
  Old        SD         6.03        3.89        9.85        8.47       6.08         11.87
            mean        87.37      89.38        7.95        86.39      85.98        12.82
 Total       SD         8.28        5.77        9.71        8.55       7.15         11.70
Table 1: means and standard deviations (SD) of A’ critical lures, A’ studied words and unrelated
words endorsed by young and old adults within the control and articulatory suppression (AS)
experimental conditions.



                                              17
Unrelated words:

A mixed ANOVA, with one within subject factor of “experimental condition” (2

levels: control and AS) and one between subjects factor of “age” (2 levels: young and

old), revealed that there was no main effect of age on unrelated words, but that there

was a significant main effect of experimental condition on unrelated words (F=16.84,

df=1, p<0.01). Participants falsely recognised more unrelated words in the AS

condition (mean = 12.82) than in the control condition (mean =7.95), and post hoc

analysis using repeated measures ANOVAs found that this effect was present in both

old adults (F=11.506, df=1, p<0.01) and young adults (F=5.61, df=1, p<0.05). This

pattern of results is depicted in Figure 1.




                       20.00
   % Unrelated Words




                       15.00

                                                              Young
                       10.00
                                                              Old

                        5.00


                        0.00
                               Control             AS

                                Experimental Condition

Figure 1: graph to illustrate the mean numbers of unrelated words falsely
recognised by young and old adults across the different experimental conditions.



A’ Studied words:

A mixed ANOVA, with one within subject factor of “experimental condition” (2

levels: control and AS) and one between subjects factor of “age” (2 levels: young and

old), revealed that there was no main effect of age on A’ studied words but that there

was a significant main effect of experimental condition (F=22.40, df=1, p<0.01).

More A’ studied words were correctly recognised in the control condition (mean =



                                                         18
89.38) than in the AS condition (mean = 85.98) and post hoc analysis using repeated

measures ANOVAs found a similar effect in both the young adult group (F=9.02,

df=1, p<0.01) and the old adult group (F=14.17, df=1, p<0.01). This pattern of results

is depicted in Figure 2.




                     95.00
   % Studied Words




                     90.00
                                                              Young
                                                              Old
                     85.00




                     80.00
                             Control             AS

                              Experimental Condition

Figure 2: graph to illustrate the mean numbers of studied words correctly
recognised by young and old adults across the different experimental conditions.




A’ Critical lures

A mixed ANOVA, with one within subject factor of “experimental condition” (2

levels: control and AS) and one between subjects factor of “age” (2 levels: young and

old), revealed that there was no main effect of age or experimental condition but that

there was a significant interaction between experimental condition and age (F=4.77,

df=1, p<0.05). Post hoc analysis using repeated measures ANOVAs revealed that the

experimental condition had no effect in the young adult group (F=0.52, df=1, p=0.48)

but that it was significant in the old adult group (F=6.95, df=1, p<0.05), where old

adults falsely recognised more A’ critical lures in the control condition (mean =

89.11) than in the AS condition (mean = 86.17). This pattern of results is depicted in

Figure 3.




                                                       19
                         90.00

     % Critical Lures


                                                                                                                    Young
                         85.00
                                                                                                                    Old




                         80.00
                                              Control                        AS

                                                  Experimental Condition

Figure 3: graph to illustrate the mean numbers of critical lures falsely
recognised by young and old adults across the different experimental conditions.




An analysis of the relationship between critical lures and studied words was also

carried out within both experimental conditions. A’ studied words were positively

correlated with A’ critical lures in both the control condition (r=0.55, p<0.01) and the

AS condition (r=0.79, p<0.01). These correlations are illustrated in figure 4.




                                                  AS                                                                           Control

                        100                                                                              100

                        95
                                                                                                         95
                                                                                       % Studied Words




                        90
   % Studied Words




                        85                                                                               90

                        80
                                                                                                         85
                        75

                        70                                                                               80

                        65
                                                                                                         75
                        60
                        55                                                                               70
                              55   60   65   70    75   80   85   90   95   100                                55   60    65   70   75   80   85   90   95   100

                                             % Critical Lures                                                                  % Critical Lures

Figure 4: scatter plots to illustrate the correlations between studied words and critical lures in
the control and AS conditions.




                                                                                  20
Free recall analysis:

A mixed ANOVA revealed that there were significant main effects of experimental

condition (F=38.624, df=1, p<0.01) and age (F=26.926, df=1, p<0.01) on the number

of words recalled, but there was no interaction between them. Participants recalled

more words in the control condition (mean = 43.79) than in the AS condition (mean =

30.36), and young adults recalled more words than old adults in both the control

(t=3.714, df=63, p<0.01) and AS (t=3.853, df=63, p<0.01) free recall tasks.



Differences between the signal detection analysis (A’) and the standard correction

(SC) procedures for the current results:

The analysis using the SC procedure produced similar patterns and results to those of

the A’ correction procedure. The only difference was that, in the SC procedure, no

significant interaction was found between experimental effect and age in the number

of critical lures produced. However, there was a trend toward significance (F=3.246,

df=1, p=0.076), and when young and old adults were analysed separately, the results

were the same as the A’ analysis, in that there was a significant effect of experimental

condition on old adults (F=4.423, df=1, p<0.05) but not on young adults (F=0.515,

df=1, p=0.478). A possible reason for the lack of interaction in the SC analysis might

be due to the large amount of variance in SC critical lures in the young adult group

(SD=27.17).




                                           21
Discussion

Previous studies using false recognition paradigms such as this one have found that

amnesic patients recognise fewer false recognitions than healthy adults (eg. Schacter

et al., 1996; Budson et al., 2000; Gallo et al., 2006), and it has been concluded that

this is due to a damaged gist memory in the patient group (eg. Budson et al., 2000;

Gallo et al., 2006). The main objective of Experiment 1 was to see if a similar pattern

of results could be produced in a healthy sample (ie. participants with an in tact gist

memory) whose item-specific memory was reduced so that it reflected that of an

amnesic patient.



The analysis of the studied and unrelated words suggests that this may indeed be

possible. There was a clear effect of experiment on both studied and unrelated words,

where young and old adults both recognised significantly more studied words and

significantly less unrelated words in the AS condition than in the control condition.

This mimics the pattern of results of previous studies which find that amnesic patients

produce less studied words and more unrelated words than healthy controls (eg.

Schacter et al., 1996; Budson et al., 2001). However, the analysis of critical lures in

this experiment does not bear such a clear resemblance to these studies. They find

that amnesic patients produce less critical lures than healthy adults (eg. Schacter et al.,

1996; Budson et al., 2000; Gallo et al., 2006), while the results of this study find that

there was no main effect of experiment with respect to critical lures. However, there

was a significant interaction between experiment and age, which revealed that, while

there was no effect of experiment in the young adults, old adults produced

significantly less critical lures in the AS condition than in the control condition. It

would appear then, that the results from the old adults do reflect those of previous



                                            22
studies that compare amnesic patients to healthy controls, while the results from

young adults do not.



Since critical lures are taken as the key measure of one’s gisting ability, this age

difference raises some issues about the theories on gist and its relationship to item-

specific memory put forward in this paper. Indeed, if these theories are to carry any

weight at all, they need to be able to account for this interaction. One possible

explanation posits that the AS task did not reduce the item-specific memory of young

and old adults to the same level. The theory proposed by this paper is that item-

specific memory needs to be above a certain threshold in order for one to gist

effectively, and hence if one’s item-specific memory is below this level one should

produce very few critical lures. However, beyond this threshold, an increased item-

specific memory should result in a reduction of critical lures, since one should be able

to use this memory to suppress the false gist representations now available to them.

Hence, if one’s item-specific memory were to be reduced to a level that is still above

the threshold, they would not produce fewer critical lures than when their item-

specific memory was unaltered, and should in fact produce more. This might be the

case in the current experiment, wherein the AS task reduced the item-specific memory

of old adults to a level below the threshold, but failed to do so with the young adults.

Evidence that the AS task reduced the item-specific memory of old adults more than it

did young adults can be found in the analysis of the AS free-recall tests, in which

young adults recalled significantly more words than old adults. Hence, it is argued

that the reason the young adults did not produce less critical lures in the AS condition

is because the AS task did not reduce their item-specific memory enough to impair

their access to gist memory. In the old adult group, however, item specific memory



                                            23
was reduced to a level that prevented them from gisting and they thus produced less

critical lures than in the control condition. Explained as such, the results of this

experiment are in keeping with the general theory espoused by this paper.



There are a couple of potential problems with this argument however. The main issue

is that dual-task performance might be the reason behind why the AS task reduces

item-specific memory of old adults more than that of young adults. Previous studies

have demonstrated that old adults are worse at dual-task performance than young

adults (Hartley, 1992; McDowd and Shaw, 2002), and if this were the case in the

present experiment, it could be that the cognitive load required by the old adults in

performing the AS task might have interfered with their ability to gist. Hence, the

fact that they were less able to gist in the AS condition than in the control condition

may not be due their reduced item specific memory, but rather it could be an effect of

their poor performance on dual-tasks.



Another hole in the argument concerns the assumption that, above a certain threshold,

an increase in item-specific memory should reduce the number of false recognitions

of critical lures. If the AS task failed to reduce the item-specific memory of young

adults to a level below this threshold, but did reduce it with respect to the control

condition, we might expect young adults to produce more critical lures in the AS

condition than in the control condition, and no such result was found. One possibility

is that the assumption itself may be inaccurate. The theory that an increased item-

specific memory reduces the number of critical lures produced was inferred from

previous experiments which found that old adults produced more critical lures than

young adults (Schacter, Koustaal et al., 1997; Norman and Schacter, 1997). Since



                                            24
young adults have a better item-specific memory than old adults, it was assumed that

they could use it to override false gist representations more so than old adults.

However, other experiments failed to find this effect of age on critical lures

(Kensinger and Schacter, 1999; Budson, 2000), and this experiment failed to do so as

well. In addition, in the current experiment, the results from the free-recall tests in the

control condition imply that the item-specific memory of the young adults was better

than that of the old adults. Thus if the theory is correct, it is strange that no effect of

age was observed with respect to critical lures in this experiment. The analysis of the

relationship between critical lures and studied words challenges this theory as well,

since there was a positive correlation between these two. If the theory were correct,

one might expect the correlation to be in the opposite direction, since studied words

represent a rough measure of item-specific memory and an increase in item-specific

memory should, according to the theory, result in a decrease in the number of critical

lures endorsed.



However, whilst these results do clash with previous findings, and the initial

predictions for this experiment, that old adults produce more critical lures than young

adults, they can still be explained by the underlying theory advocated in this paper.

That is that an increased item-specific memory, whilst being able to oppose gist

memory in one sense, might at the same time enhance it, since the more items one has

available to them, the better equipped they are to gist. Therefore, while someone with

a better item-specific memory might override more false gist representations than

someone with a weaker item-specific memory, their gist memory would also be

enhanced, and so they might at the same time be producing more and stronger gist

representations, and it is possible that the outcome of this would be an unobservable



                                             25
difference between the two persons. In other words, young adults might suppress

their false gist representations more than old adults, but still produce the same number

of critical lures, since their gist memory would also be stronger. In addition, whilst it

is hypothesised that gist memory is considerably influenced by item-specific memory,

it is not entirely dependent on item-specific memory, and it exists as a type of

memory in its own right. Hence there is room for variation in how much people gist

off the same information. This implies a complicated and unpredictable interaction

between gist and item-specific memory, but it does seem to account for the

inconsistent results on the age difference in critical lures. Whether or not it is

accurate, the mixed findings on this matter must at the very least suggest that the

relationship between item-specific memory, gist memory and number of critical lures

produced is not as clear cut as it has previously been made out to be.




                                            26
Experiment 2: Case study of patient JY

JY is 30 years old and suffers from a developmental amnesia, possibly as a result of

birth asphyxia. She displays markedly poor immediate and delayed verbal recall but

relatively in tact verbal recognition. Her visual memory is impaired for both recall

and recognition. Her executive functions seem mostly unaffected, and she

demonstrates only a slight slowing in information processing. She has been

diagnosed as presenting “a clear amnesic syndrome, with preserved executive

functions”.



The current experiment compares JY’s performance on two tests of false recognition,

both in relation to each other and to healthy young and old adults as well. One of

these tests is a control condition, and the other requires that JY is brought to criterion

on all of the word lists used in the test before undertaking it. The purpose of bringing

JY to criterion is to improve her item-specific memory for these lists to a level

approaching that of a healthy adult. This paper hypothesises that amnesia does not

damage gist memory directly, and that the reason previous studies have found a

reduced number of false recognitions in these patients (eg. Schacter et al., 1996;

Budson et al., 2000; Gallo et al., 2006) is because their impaired item-specific

memory prevents them from accessing their gist memory, and not because their gist

memory itself is damaged. It is thus predicted that, in the control condition, JY will

produce less false recognitions than healthy young and old adults, since her item-

specific memory is too low for her to gist effectively. However, after being brought

to criterion, it is predicted that she will produce more false recognitions than in the

control condition, since her item-specific memory will have been improved to a level

that her gist memory is able to act on. In addition, it is predicted that after being



                                            27
brought to criterion, JY will produce more false recognitions than young and old

adults, since her source monitoring ability is likely to be worse (for a review on

source memory in amnesia, see Johnson et al, 1993) and it is also unlikely that her

item-specific memory will be able to be improved to the same level.



Method:

Materials and tasks:

False recognition and free recall tests: There were two false recognition tests (A and

B) and two free recall tasks and these were exactly the same as those describe in

Experiment 1.



Criterion lists: JY was brought to criterion on all of the word lists used in false

recognition test B. The criterion lists were thus the same lists as those used in that

paradigm (see appendix A, list B for a table of the lists used). There were twelve lists

and each list consisted of fifteen words. Each word was printed on an A5 sized

flashcard.



Procedure:

The full experiment was divided into two sections as it was very time consuming. JY

was told that most of the experiment would take place on the computer and that in

addition there would be a few tests carried out in person, and the general procedure

for the false recognition tests, free-recall tests and the criterion phase was described to

her. In the first section, she carried out false recognition test A. She then had a half

hour break before starting the second section. JY began the second section by being

brought to criterion on all twelve of the criterion lists. The procedure for this was as



                                            28
follows: For each of the lists, JY was instructed to try to remember as many words as

possible. The list was then presented, one word at a time and for approximately 2

seconds each word. After the last word was presented, she was told to recall as many

of the words as possible in any order. The number of words correctly recalled was

recorded on a score sheet. The same list was then presented again in exactly the same

manner, and again the number of words correctly recalled was recorded. This process

was repeated with the same list until either JY recalled 7 or more items correctly, or

she failed to increase her score from the previous trial. This whole procedure was

repeated for each of the twelve lists. Once JY had been brought to criterion on all of

the lists, she completed false recognition test B.



Results:

The same correction procedures used in experiment 1 were applied to JY’s results and

for the same reasons as before, it is the A’ analysis which is presented here.

However, as in the first experiment, any differences in results between the A’ and SC

procedures are mentioned at the end of the results section.



Table 4 shows the mean percentages of A’ critical lures, A’ studied words and

unrelated words endorsed by JY in each experimental condition, and this pattern of

results is illustrated in Figure 6. After being brought to criterion, she produced more

A’ critical lures (mean = 92.95) than in the control condition (mean = 64.29), more A’

studied words (mean = 96.69) than in the control condition (mean = 70.09), and less

unrelated words (mean = 8.33) than in the control condition (mean = 41.67).




                                            29
                                                   Control                                               Criterion
                               A' Critical       A' Studied        Unrelated      A' Critical          A' Studied      Unrelated
                               lures             words             words          lures                words           words

mean                                   64.29             70.09            41.67           92.95                96.69           8.33
Table 4: mean percentages of A’ critical lures, A’ studied words and unrelated words endorsed
by patient JY in the control condition and after being brought to criterion.




                      100.00

                       90.00

                       80.00
   % Words Endorsed




                       70.00

                       60.00                                                       A' Critical Lures
                       50.00                                                       A' Studied Words

                       40.00                                                       Unrelated Words

                       30.00

                       20.00

                       10.00

                        0.00
                                       Control                Criterion

                                       Experimental Condition

Figure 6: graph to illustrate the pattern of means of A’ critical lures, A’ studied words and
unrelated words endorsed by JY in the control condition and after being brought to criterion.




JY’s results were compared to those of healthy adults using a significance test devised

by Crawford and Howell (1998). First, JY’s results from the control condition were

compared to those of healthy young and old adults in the control condition. It was

found that JY produced less critical lures than both young and old adults (young: t=-

2.122, df=31 p<0.05; old: t=-4.057, df=32, p<0.01), more unrelated lures than both

young and old adults (young: t=3.591, df=31, p<0.01; old: t=3.258, df=32, p<0.01),

and with regard to A’ studied words, while she did not produce significantly less than

either young or old adults there was a trend towards significance in both cases (young:

t=-1.857, df=31, p=0.073; old: t=-1.869, df=32, p=0.071). After being brought to




                                                                          30
criterion, JY’s “criterion” results were compared to healthy adults in the control

condition, and there was no significant difference in A’ critical lures, A’ studied

words or unrelated words between JY and healthy adults.



Differences between the signal detection analysis (A’) and the standard correction

(SC) procedures for the current results.

When JY’s results from the control condition were compared to those of healthy

adults in the control condition, the SC analysis failed to produce the significant

difference that the A’ analysis did between JY and young adults with respect to

critical lures. With regard to the studied words, the only difference was that the SC

analysis produced a significant difference between JY and old adults (t=-3.197,

df=32, p<0.01), while the A’ analysis only found a trend towards a significant result.



When JY’s results in the control condition were compared to healthy young and old

adults in the AS condition, the SC analysis failed to produce a significant difference

between JY and these groups with respect to critical lures and studied words, unlike

the A’ analysis. However, there were trends towards significance in the old adults

with respect to both critical lures (t=-1.755, df=33, p=0.089) and studied words (t=-

1.862, df=32, p=0.072).



All other results were the same, and as in experiment 1, the differences could be due

to the large amount of variance found in SC data, as compared to that found in the A’

data.




                                           31
Discussion:

The main objective of experiment 2 was to see if improving the item-specific memory

of patient JY would increase her ability to gist, and the results suggest that it did.

After being brought to criterion, JY showed clear signs of increased gisting as she

produced more critical lures, more studied words and less unrelated words than in the

control condition. The results also suggest that, in line with predictions, JY was less

able to gist than young and old adults when they were all in the control conditions,

since she produced less critical lures and more unrelated words, and also showed

trends towards producing less studied words. This is in keeping with the findings of

previous studies which show that amnesic patients produce less false recognitions

than young and old adults (Schacter, Verfaellie et al., 1997; Norman and Schacter

1997). After being brought to criterion, it was predicted that JY would produce more

false recognitions than young and old adults since, though she should be gisting at

roughly the same level, her source monitoring ability should still be considerably

worse (for a review, see Johnson et al., 1993). However, the results show that there

were no differences between JY and young and old adults with respect to critical

lures, studied words or unrelated words, and thus imply that JY was able to gist at the

same level as both young and old adults. A possible reason for this is that, in bringing

her to criterion, seeing the lists several times might have strengthened her memory for

the source of the words, and this could have allowed her to exclude some of the false

gist representations in the same way that healthy adults do. Another interpretation

refers to the theory expressed in the discussion in Experiment 1 about the interaction

between item-specific memory and gist memory. It could be that JY’s item-specific

memory was not increased to as high a level as that of the young and old adults, and

therefore although they might have been able to override more false gist



                                            32
representations than her, their gist memory would also have been stronger, and hence

the gist representations they experienced might have been greater in number and

strength. Hence despite any differences that might have existed between JY, young

adults and old adults with respect to gist memory, item-specific memory and their

interaction, the observable outcome (ie. number of falsely recognised critical lures)

could still be the same.



These results demonstrate that JY showed signs of healthy gisting when her item-

specific memory was increased, but signs of impaired gisting in the control condition

when her item-specific memory was very low. This implies that her gist memory was

in tact (since it worked fine when her item-specific memory was increased), despite

the fact that she produced less false recognitions than young and old adults in the

control condition. This stands in stark contrast to the conclusions drawn by previous

studies (eg. Budson et al., 2000, Gallo et al., 2006) which claim that a damaged gist

memory is precisely the reason behind why amnesic patients produce less false

recognitions than healthy controls. Although this is only a case study, and one on a

patient whose amnesic syndrome is different from those studied previously, it still

points towards a possible error in the previous studies’ assumptions that gist memory

is damaged in amnesic patients. This is because the pattern of results found when JY

was in the control condition was exactly the same as that found in various

experiments on different amnesic patients (eg. Korsakoff’s patients: Schacter,

Verfaellie et al.,1997; AD patients: Budson et al, 2000; patients with mixed

etiologies: Schacter et al., 1996), and since it is these results that have led to

assumptions of impaired gist memory, it could be that that the assumptions have not

adequately accounted for the effect of item-specific memory in the results. On a more



                                             33
theoretical level, these results support the theory put forward by this paper that there

is an interaction between gist memory and item-specific memory, since when JY’s

item-specific memory was increased she showed signs of improved gisting. More

specifically, the results are also in line with the idea of a threshold whereby one

cannot gist effectively if their item-specific memory is below a certain level, since in

the control condition when JY’s item-specific memory was very weak, she produced

significantly less critical lures than the older adults.



There is a potential problem, however, with the suggestion that the increased number

of critical lures in the criterion condition is due to JY’s increased item-specific

memory. JY was brought to criterion on the various study-lists in the false

recognition paradigm by presenting them to her several times. While it is true that

this might have increased her item-specific memory for the individual words on the

lists, it might also have increased her gist memory for the lists in general. A repeated

trials experiment by Budson et al. (2000) found similar results, in that the number of

critical lures and studied words recognised by AD patients increased over trials, but

these researchers argued that this increase was due to the AD patients’ damaged gist

memory improving with the repetition. Since the method for bringing JY to criterion

did not isolate her item-specific memory from her gist memory, this argument could

theoretically apply to her results as well. However, the experiment by Budson et al.

(2000) did not isolate AD patient’s item-specific memory from their gist memory

either, and thus the explanation given for JY’s results (that the increase in critical

lures is due to an increase in item-specific memory) could just as easily apply to the

results of Budson et al’s study. Indeed, the fact that the number of studied words

increased over trials in Budson et al.’s study suggests that AD patients’ item specific



                                             34
memory was increasing, even if their gist memory was as well, so the possibility that

this caused the increase in critical lures should at least be acknowledged. In sum, it

seems likely that when study-lists are presented to amnesic patients several times, it

results in an increase in both item-specific and gist memory, but a question remains

over whether it is the increase in item-specific memory that causes the increase in gist

memory. Neither the present experiment or previous experiments (Budson et al,

2000) manage to answer this question effectively as they both fail to isolate the effects

of item-specific memory and gist memory on false recognitions. However, it is

important to recognise the fact that an increasing item-specific memory could account

for the results of previous experiments (eg. Schacter et al., 1996; Budson et al., 2000;

Gallo et al., 2006) and thus that their assumptions that gist memory is damaged in

amnesic patients are not conclusive.




                                           35
General Discussion:

Previous studies using false recognition paradigms such as this one have found that

amnesic patients falsely recognise fewer critical lures than healthy adults (Schacter et

al., 1996; Budson et al., 2000), and it has been concluded that this is due to a damaged

gist memory in the patient group (eg. Budson et al., 2000; Gallo et al., 2006).

However, it may instead be that this pattern of results is due to the severely impaired

item-specific memory of the amnesic patients, which may be too low for their gist

memory to act on. In other words, it might be that their ability to gist is in tact and it

is rather their access to it which is impaired. This was the initial theory proposed by

the current paper and it is supported, to an extent, by the results from Experiments 1

and 2. Experiment 1 supports the theory by demonstrating that reducing the item-

specific memory of healthy old adults produced a similar pattern of results to that

shown by amnesic patients, as healthy old adults produced less critical lures in the AS

condition than in the control condition. Since gist memory in these adults was in tact,

the results suggest that reduced recognition of critical lures does not necessarily

reflect a damaged gist memory, but could instead be a consequence of a weak item-

specific memory. Experiment 2 supports the theory by demonstrating that when the

item-specific memory of amnesic patient JY was increased, she was able to gist as

well as healthy adults, which implies that her gist memory was in tact. However, she

produced less critical lures than healthy adults when in the control condition (where

her item-specific memory was very weak), and this again suggests that a reduction in

critical lures does not necessarily reflect a damaged gist memory but might rather be

due to a weak item-specific memory.




                                            36
However, there were several inconsistencies in the results of both experiments and

these raised some interesting questions about the relationship between item-specific

memory and gist memory. These questions were addressed in the discussion sections

of each experiment and a theory about this relationship was suggested in order to

account for the results. This theory is similar to that put forward in the introduction,

in that it maintains that an increased item-specific memory might both enhance one’s

gist memory and suppress it at the same time. However, before it was assumed that

an increase in item-specific memory would suppress gist memory more than it would

enhance it, as this explained why old adults produced more false recognitions than

young adults, but the evidence from Experiment 1 and others (Kensinger and

Schacter, 1999; Budson et al., 2000) that old adults do not produce more false

recognitions than young adults, suggest that this is not always the case. Gist memory

exists in its own right, and hence while it is heavily influenced by item-specific

memory, in being strengthened or suppressed, this is not the only factor that

determines how much or how well someone gists. Hence, individual differences in

gist memory could mean that two people with the same item-specific memory might

produce different numbers of critical lures. On top of this, it is still assumed that a

certain level of item-specific memory is required in order to for the gist memory to act

on, and without this, one cannot gist effectively. So in summary, the theory states that

in the first place, item specific memory acts a gateway to gist memory, whereby a

certain level of item-specific memory is needed to allow gist memory to become

active. After this point, however, the situation becomes very complex, since an

increase in item-specific memory both strengthens gist memory and suppresses it, and

this can happen to different extents depending on the gist memory of the individual

and any other factors which might influence it.



                                            37
This theory accounts for the findings that amnesic patients recognise less critical lures

than healthy adults (eg. Schacter et al., 1996; Budson et al.), since the item-specific

memory of these patients is severely impaired and could therefore be too low to gist

effectively. It therefore challenges the assumption that amnesic patients have an

impaired gist memory, since the results that led to this assumption can be explained

differently. Other studies use “semantic categorisation” to test for gist memory in a

different way (Koustaal et al., 1999; 2001; 2003; Budson, 2006). These experiments

ask participants whether they recognise items as being part of a particular category,

and false recognitions in these paradigms are seen as a better measure of gist as the

possibility of source monitoring errors is greatly reduced. The results of amnesic

patients in these studies show the same pattern as before, whereby they falsely

categorise more items than healthy adults, and again this result has been used to infer

a degraded gist memory in amnesia (Koustaal et al. 2001; Budson, 2006). However,

the theory proposed by this paper can account for these results in the same way that it

did for the false recognition results of amnesic patients. It could be that the amnesic

patients’ impaired item-specific memory for the pictures prevents them from gisting

effectively, and hence they produce fewer false categorisations. Therefore the results

of semantic categorisation experiments do not necessarily point to a damaged gist

memory either.



Other experiments have explored ways to reduce false recognitions, such as with the

use of a distinctiveness heuristic (eg. Israel and Schacter, 1997), or through repetition

of study-test trials (Budson et al., 2000). The distinctiveness heuristic is a method of

making items more distinctive, and experiments find that this reduced the number of



                                           38
falsely recognised critical lures in young and old adults (Schacter et al., 1999; Dodson

and Schacter, 2002), but not in AD patients, who even showed a slight increase in

false recognitions (Budson et al., 2002). Again this result has been used to infer that

the patients have a damaged gist memory, but again the theory proposed by this paper

can account for these results in a different way. It seems that increasing the

distinctiveness of items improved one’s item-specific memory for them, which

enabled healthy adults to suppress more false gist representations and hence recognise

fewer critical lures. While the interaction between item-specific and gist memory

advocated by this paper is thought to be complex and perhaps unpredictable, this

possibility is still accounted for. The theory can also account for the results of the AD

patients, by positing that while the distinctiveness heuristic may have improved their

item-specific memory to a degree, this may still not have been strong enough to

suppress their false gist memories. This would even explain the slight increase in false

recognitions found in Budson et al.’s experiment (2002). A similar explanation can

be used to account for the results of the repeated trials experiment (Budson et al.

2000). These showed that that repetition of the study-test procedure reduced the

number of false recognitions in healthy young adults, had no effect on the number of

false recognitions in healthy old adults, and increased the number of false

recognitions in AD patients. It was inferred that the repetition improved the item-

specific memory of healthy young adults, which enabled them to suppress their false

gist memories, but did not affect the item-specific memory of the old adults. The

increase in false recognitions observed in the AD patients was explained in terms of

an impaired gist memory that improved with the repetition of trials. The theory

posited by this paper can explain these results differently, and without the assumption

of a damaged gist memory in the AD patients. It would suggest that, in all the groups,



                                           39
item-specific memory and gist memory was improved with the repetition of trials, but

to different levels. The item-specific memory of the young adults was improved the

most, and to a level that could substantially suppress even their improved gist

memory. The old adults’ item specific memory increased to a level that suppressed

their improved gist memory enough to prevent an increase in false recognitions but

not enough to cause a reduction. Finally, the AD patients’ item-specific memory was

increased to a level that allowed access their gist memory but it was not high enough

to suppress the false gist representations now available to them.



It would appear, therefore, that this theory can account for many of the results of

different false recognition experiments. The current experiment supports this theory

and hence provides evidence that previous studies might be mistaken in their

assumptions that gist memory is damaged in amnesic patients, since this theory can

explain their results without reference to a damaged gist memory. However, while

this experiment suggests that gist memory might be in tact in amnesic patients, it does

not offer any evidence that gist memory actually is in tact in these patients.

Experiment 2 attempts to demonstrate this, but ultimately falls into the same trap as

other false recognition experiments, as it fails to isolate gist memory from item-

specific memory. However, along with Experiment 1, it does demonstrate the

possibility that item-specific memory plays an influential role in one’s ability to gist.

Indeed if the theory suggested in this paper is correct, it would seem that there is an

extremely complex and interactive relationship between the two types of memory.

Hence, if false recognition tests are to be a useful means of assessing one’s ability to

gist, they need to find a way to account for this intricate relationship and somehow

isolate the effects of item-specific memory from those of gist memory. However, this



                                            40
would seem to be impossible, since these tests of false recognition all require

participants to explicitly study related lists, and in doing so their item-specific and gist

memories become immediately intertwined. Hence, the results of these tests can only

truly reflect the relationship between item-specific memory and gist memory, and

cannot accurately asses the effects of either on its own. Since this relationship

appears to be highly complicated, variable and also unpredictable at times, it is

suggested that false recognitions are not particularly beneficial as a measure of gist

memory, and thus that there is a need to find new methods of doing so. One possible

approach would be to bypass item-specific memory entirely and attempt to access gist

memory via implicit memory. This suggestion is influenced by Balota et al’s work on

semantic memory in amnesic patients (Balota et al., 1999, Watson et al., 2001.), and

following their lead, using semantic-priming exercises to assess gist memory could be

a possible avenue for a new approach.




                                            41
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                                           49
                                                                APPENDIX A

                           Paradigm A                                                                          Paradigm B
 Anger         Fruit      Bread        Cold         Doctor         King           Black       Chair      Foot         Galaxy          High         Man
   rage        apple       butter       hot          nurse        queen           white        table     shoe            stars          low      woman
   fear       basket         jam        ice        hospital        royal           dark         legs      ball        universe          sky         boy
   hate         tree       board      winter           ill         ruler            cat        stool     mouth         planet            tall     uncle
    fury       juice     sandwich       wet        injection      prince           blue         seat       toe            bar         tower      person
    red        pear         flour     freeze        health        crown          funeral       back      ankle          space       airplane       wife
 temper         ripe        milk       snow      stethoscope     England          colour       desk      sock         cosmos        altitude       male
violence       salad       yeast      frozen        patient       palace           grief      wood        sole         infinite       flying      father
  wrath       banana      dough        chilly    prescription     throne          green         sofa      walk       Milky-Way          kite      strong
   fight    strawberry     crust       heat           pills       chess           death     cushion      smell       black hole        rise       friend
  chaos       orange          roll   weather      treatment     sovereign           ink       sitting     boot         nebula            far      beard
  hatred      dessert       slice     fridge         office      subjects        bottom       swivel       run      constellation    vertigo      being
  mean      vegetables     wine         air        medical      monarch            coal     furniture     sore        satellite      hopes      handsome
emotion        bowl          loaf     shiver       surgeon        castle          brown         arm       step          moon          giant      muscle
shouting      cocktail     toast       Arctic        clinic       leader          raven      rocking     odour            sun          lofty        suit
 enrage        berry         bap       frost          cure         reign           grey       bench      hand         asteroid       mighty         old

Mountain     Needle        Rough       Slow        Spider        Sweet            River       Sleep        Soft         Thief       Window       Music
    hill      thread      smooth        fast          web           sour          water      dreams        hard         steal         pane         note
  steep         pin         ready      down         insect        sugar          stream         bed       warm         robber         glass       sound
  climb         eye        ground      quick           fly         tooth           lake        night    comfort         crook        ledge          pop
 summit      sewing         tough       snail     arachnid      chocolate         wide        pillow    feathers      burglar          sill       score
    top        sharp     sandpaper      stop         crawl        good             boat       awake        cosy       money         curtain       sheet
 molehill      point      stubble     coach       tarantula        taste            tide      peace      cuddly        police        frame        stave
   peak        prick      surface      delay       poison         sticky          swim          rest     gentle          bad         house         song
   plain     thimble       coarse      traffic        bite          nice           flow      slumber      touch          law          open         book
 glacier    haystack      uneven     tortoise      creepy         honey            runs        doze        fluffy         jail      broken       stereo
   goat        thorn       justice   hesitant      animal         syrup           barge        tired       furry      criminal       closed      singing
   bike         hurt       rugged     speed           ugly        toffee          creek       snore      downy          villain       view        guitar
 climber       sting          cut       bus        feelers        heart           brook         nap       kitten        crime       breeze       record
  range        stitch        bark    sluggish        small         cake             fish   nightmares       skin        bank          sash        piano
  valley       cloth        rocky       wait        nasty        wrapper         bridge        yawn      tender      dishonest        soul         tune
    ski      knitting       gravel       idle        eerie           pie         winding     drowsy       snug         pillage      shutter     orchestra


             Appendix A: table showing all the words and lists used in the false recognition paradigms A and B.
                  The critical lure for the list is written in bold above the actual list that was presented.




                                                                APPENDIX B

                                          LIST A                                           LIST B
                                           Labour                                            Candle
                                            Gravy                                            Famish
                                          Hamster                                             Blot
                                          Astonish                                            Scent
                                          Daffodil                                            Halt
                                           Refuge                                             Tool
                                          Pamphlet                                             Zoo
                                           Swamp                                             Novice
                                         Toothbrush                                          Chance
                                           Vacant                                             Grunt
                                            Boast                                           Wallpaper
                                          Connect                                           Bacteria
                                           Fashion                                           Camera
                                           Abrupt                                            Unique
                                            Urban                                            Major

                                 Appendix B: table showing the words used in the two free recall lists




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