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```					  De-biasing Anchoring and
Adjustment: The Use of Multiple
Anchors
Bridgett Milner
Ed Hirt
MPA Presentation
Thanks to:
Amy Johnson, Kelly Koch, Erin Steury,
and Kristin Hendrix
(a brief review)

• The anchoring and adjustment heuristic
involves the significant influence of an
arbitrary reference point (an anchor) on
estimates and judgments (Tversky and
Kahneman, 1974).
o Is Mt. Everest taller or shorter than 10 miles?
How tall is Mt. Everest?
• 5.5 miles
More on Anchoring and
• Anchoring and adjustment allows for judgments
to be made under uncertainty conditions,
through allowing the individual (most often) a
reasonable starting point from which to adjust
(Tversky and Kahneman, 1974).
• The influence of this anchor is such that
judgments are insufficiently adjusted away from
this reference point (the anchor) toward the true
value.
Bias
• The use of this strategy, or heuristic,
typically causes a bias in estimates
reflected in this insufficient adjustment,
such that judgment is biased toward the
initial values presented (the anchor). Bias
becomes more extreme as anchor points
become more extreme relative to the true
value.
Standard Anchoring Procedure
• Most often demonstrated through the standard
anchoring paradigm in which participants are
given an anchor to which they make two
responses. These responses are:
1. a “comparative” judgment
• asked to compare the anchor to their estimate or target
response (most often asked to judge whether the actual,
true value is above or below the supplied anchor)
2. an “absolute” judgment
• asked to give their best estimate of the target response
(or the “true” value).
Example of Standard Anchoring
• Is the percentage of African Nations in the
UN greater or less than ____? (e.g.,65%
or 10%)
– Respond
• What is the number of African Nations in
the UN?
– Respond (mean estimate of high anchor =
45%, mean estimate of low anchor= 25%)
Robust
• Regardless of type of anchoring task used,
findings are quite robust. Anchoring occurs in
many paradigms and with many types of
estimates including those on issues individuals
care deeply about such as nuclear war
estimates.
• Anchoring occurs even when the anchor
provided is irrelevant to the study question
(such as an assigned participant number or a
completely unrelated statistic) or so extreme as
to be completely implausible as a response.
Really Robust
• Anchoring has been demonstrated in
information rich real world settings and
with experts in the anchoring estimation
task (Northcraft and Neale, 1987).
Avoiding the Bias—Background for
this Study
• Use of the anchoring and adjustment heuristic in
decision making seems fairly unavoidable.
– laboratory experiments find that participants are often
completely unaware that an anchor influenced their
response (Tversky and Kahneman, 1974; Northcraft and
Neale, 1987, many others).
– when told about anchoring and adjustment and warned to
avoid the use of this heuristic, effects remain (Plous, 1993).
– attempts at accuracy such as monetary incentives for
correct judgments have no effect (Wilson, Houston, Eitling, &
Brekke, 1996).
– To date, within traditional anchoring studies, the only time in
which bias was not found was when participants had not
paid attention to the supplied anchor (Wilson et al,
1996)…well sort of (we’ll get to that)
Mechanism: SAM – More
Background for this Study
• Mussweiler and Strack’s Selective Accessibility
Model is used to account for anchoring findings.
– When given an anchor, initially set value as equal to
anchor. Test this using a positive test strategy
which selectively scans ones memory for
supporting evidence. This scan causes confirming
evidence to become more available. This available
information is used to make estimate.
– More robust than semantic priming due to self-
generated nature of prime.
A new attempt to de-bias (at least
in part): This study!
• Perhaps can de-bias anchoring and adjustment
in the same way one de-biases the explanation
bias in social judgment---through the “consider
the opposite technique” (Lord, Lepper, &
Preston, 1984; Mussweiler, Strack, & Pfeiffer,
2000) or “consider any plausible alternative”
(Hirt & Markman, 1995).
– De-biases through priming stimuli other than the
ones previously assessed (Hirt & Markman, 1995)---
participants use ‘simulation heuristic’ to engage in
“multiple simulation runs of potential outcomes”.
Consider the Opposite
(or the Red Sox not winning against the Yankees)

• Within social judgment (and anchoring)
considering the opposite outcome (or
anchor) de-biases social judgments.
– When first asked to think about “why might the
Red Sox win against the Yankees” –
judgments become biased and people think
“yeah, the Red Sox are going to win.”
– If asked to then think about “why the Red Sox
might not win against the Yankees”--
judgments now become unbiased.
Consider an Alternative
(or Carrie winning American Idol)

• Interestingly, work by Hirt & Markman (1995) finds that
you needn’t just consider the opposite to produce de-
biasing effects though. They found that considering any
alternative outcome (even when that outcome was in
the same direction as the original one) produced de-
biasing.
– So in their paper, when participants explained a team winning
by both a close-margin and a landslide, de-biasing occurred!
Also when explain 2 teams winning de-biasing occurs!
– So think about Bo winning American Idol---explanation bias
leads to individuals thinking this is more likely---now think
This study’s hypotheses
1. Traditional anchoring effects will occur in
standard traditional anchoring questions.
2. When participants “consider the opposite,” de-
biasing will occur.
3. When participants “consider an alternative,” de-
biasing will occur
Procedure
• 2 conditions (1 control; 1 experimental)
– Control condition asked trivia questions (given no
anchor)
– Experimental condition –standard anchoring
paradigm--(5 different questionnaires all with same
15 trivia questions---each participant responds to:
•   3 high anchor questions
•   3 low anchor questions
•   3 2-high anchor questions
•   3 2-low anchor questions
•   3 1-high 1-low anchor questions
• Prior to completing the anchoring questions
participants completed a short questionnaire
• Participants responded to
– demographic information (age, gender, and race)
– A self-report of “trivia-knowledge” on a 1-7 scale
– The NFC scale
Questions!
1.    When did the Titanic sink?
1912 Mean Cntrl=1910 anch: 1850, 1867, 1947, 1954
2.    How long is a blue whale at birth (in feet)?
25      19.45          2,     4,     44,     60
3.    How many hours does it take for a snake to digest a frog (on
average)?
50       21.2          1,     2,     34,      42
4.    How many eggs does the average American consume each
year?
286     236.4         24,     30,    400,     500
5.    In what year was the planet Neptune discovered?
1846   1829.6        1601,   1756,   1972,   1974

Etc….
Results!!
• Overall, differences between the 5
experimental conditions were found
F(4,800)=390.44, p<.001.
• Post hoc t-tests follow on the upcoming
slides as do t-tests comparing
experimental conditions with control
responses.
Traditional anchoring effects were found
– T-test comparing (z-scores of) high anchoring
conditions and control conditions
• t (293)= -6.380, p<.001
– High anchor mean = .6002
– Control mean =    -.0889
– Low conditional and control
• t (297) = 5.878, p<.001
– Low anchor mean = -.5853
– Control mean =    -.0889
Consider the Opposite
Considering the Opposite was seemingly an effective de-
biasing technique.
– Control versus High and Low anchor given btw Ss t-test
• t (299) = -.834, p=.405
– Control mean =            -.0889
– High and Low anchor mean = .0046
– High and Low anchor given leads to significantly less high
estimates than high anchor condition and significantly higher
estimates than low anchor condition.
• t (217) = 11.725, p<.001 (high vs both w/in Ss t-test)
• t (221) = -12.043, p<.001 (low vs both w/in Ss t-test)
– High mean = .5287
– Both mean = .0008
– Low mean = -.5551
Consider an Alternative
• Considering 2 anchors in the same
direction did not de-bias overall but
instead led to even more severe biasing
than single anchors .

• t (216) = -4.011, p<.001 (high vs 2-high w/in Ss t-
test)
• t (221) = 2.449, p<.05 (low vs 2-low w/in Ss t-test)
–   High mean = .5276
–   2-High mean = .6687
–   Low mean = -.5556
–   2-Low mean = -.6472
More on Consider an Alternative
• Recent follow up research by Hirt, Kardes, &
Markman (2004) finds that this consider an
alternative de-biasing strategy is moderated by
the individual difference “need for structure”
such that:
– individuals low in need for structure are more
affected by this de-biasing technique than those
who are high.
• Within their research they find in fact that for
low need for structure individuals, the
alternative considered needn’t even be in the
same domain for effective de-biasing to occur.
Need for Structure
• Need for structure is characterized by the desire to
maintain with some extent of permanence a specific
solution that has been seized upon.
• This personality characteristic is measured by facets
1, 2, and 4 of the Need for Closure scale (which can
be broken into 5 different facets [3 being decisiveness
and 5 being closed-mindedness]) (Neuberg, Judice, &
West, 1997).
• Past research has found that this individual difference
(NFS) leads to stronger anchoring effects (Kruglanski).
Need for Structure Results
• Significant differences between high and low
NFS participants were found across the 4
experimental conditions in which bias was
found (low, 2 low, high, & 2 high anchors). This
difference was always that individuals low in
NFS were significantly less biased than
individuals high in NFS.
• Low: F(1, 257)=6.41, p<.05         high=-.61 low=-.48
• High: F(1,253)=6.85, p<.01         high= .63 low=.48
• 2 Low: F(1, 254)=109.23, p<.001 high=-.78 low=-.41
• 2 High: F(1, 254)=109.23, p,.001 high= .94 low=.36
More on NFS
• For the high and low anchor conditions
(consider the opposite), all participants were
de-biased, showing no differences from the
control condition.
• For conditions in which 2 anchors were
presented in the same direction (consider an
alternative) :
– For low NFS participants, de-biasing effects were
found such that when 2 anchors were presented
participants showed less bias than in the traditional
single anchor conditions
• Low: t(114)=1.17, p=.09 1=-.48 2=-.41
• High: t(111)=2.83, p<.01 1= .49 2= .36
Continued…
– For high NFS participants, presenting 2
anchors in a single direction worked in the
opposite direction such that, rather than de-
biasing estimates, estimates became more
biased.
• Low: t(131)=3.18, p<.01   1=-.61 2=-.78
• High: t(135)=4.64, p<.001 1= .63 2= .94
Discussion---Hypotheses revisited
1. Traditional anchoring effects will occur in
standard traditional anchoring questions.
2. When participants “consider the opposite,” de-
biasing will occur.
3. When participants “consider an alternative,”
de-biasing will occur.
Discussion---Hypotheses revisited
 Traditional anchoring effects will
occur in standard traditional
anchoring questions.
 Single high anchor led to significantly
higher estimates than control and
single low anchor led to significantly
lower estimates than control.
2. When participants “consider the opposite,” de-
biasing will occur.
3. When participants “consider an alternative,” de-
biasing will occur.
Discussion---Hypotheses revisited
    Traditional anchoring effects will occur in standard traditional anchoring
questions.

 When participants “consider the opposite,” de-
biasing will occur.
 Consider the opposite condition estimates did not
significantly differ from control estimates.
3.   When participants “consider an alternative,” de-biasing will occur
Discussion---Hypotheses revisited
    Traditional anchoring effects will occur in standard traditional anchoring questions.
    When participants “consider the opposite,” de-biasing will occur.

 When participants “consider an alternative,” de-
biasing will occur.
 Consider an alternative ONLY worked as a de-biasing
strategy for participants low in need for structure. For
individuals high in need for structure, considering two
anchors in the same direction actually led to more extreme
anchoring effects.
 Individuals high in NFS (consistent with Kruglanksi’s
findings) made significantly more biased estimates in the
direction of the anchor (or anchors) than individuals low in
need for structure
Summary
• De-biasing of anchoring (like the explanation
bias) using a consider an alternative strategy is
moderated by the individual difference NFS.
– For individuals low in NFS, considering an
alternative is effective as a de-biasing technique.
– For individuals high in NFS, de-biasing is much
more difficult. For these individuals considering an
alternative does not work. To de-bias individuals
high in NFS one must really be extreme in their de-
biasing strategy and provide an opposite anchor
rather than any other anchor.

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 views: 8 posted: 9/6/2012 language: English pages: 31