Energy Management in Untethered

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					                                CS325: Usability
                                Human Abilities

                                           Mark Corner
               UMass Amherst Department of Computer Science
 As for all of the lectures in this course, the slides a a mishmash of material from various places. People that I have borrowed the
most from are Scott Klemmer and Terry Winnograd from Stanford, Jim Foley and Gregory Abowd from GaTech, James Landay from
                                                      UW, and Jason Hong from CMU




                                                                                                                        1
       Human Capabilities
• Why do we care?



• Knowing the user informs the design
  – Senses
  – Information processing systems
  – Physical responding

                                        2
                Overview
• Senses
  – Vision, hearing, touch, smell, etc.
• Information Processing
  – Perceptual, congitive (memory, processes)
• Motor System
  – Hand movement, workstation layout


                                                3
       First, some writing..
• In the reading, particular emphasis are
  placed upon arousal and selective
  attention. In what ways do you think
  these relate to modern user interfaces?




                                            4
               Senses
• Three most important to HCI?




                                 5
               Sensitivity
• Two ways to look at it
• Just Noticeable Difference
  – Change in stimulus for the user to notice
  – Weber’s Law says logarithmic
• Stimulus magnitude vs. perceived
  magnitude


                                                6
Fechner’s Law




                7
Vision




         8
 Color JND




Color, from 400 to 700 mm
V I   B   G   Y   O    R

                            9
    Which is Brighter?




(130, 130, 130)   (140, 140, 140)
                                    10
           Preprocessing
• Humans have preattentive abilities
  – Detection in low-level visual systems




           [image from Healey 2005]
                                            11
         Vision Limitations
• 30 degree viewing without moving head
• 1/30 degree is limit of differentiating
  pixels
• 8% of males and 1% of females
  “colorblind”
  – Primarily reds and greens


                                        12
         Audition (Hearing)
• Capabilities (best-case scenario)
  – pitch - frequency (20 - 20,000 Hz)
  – loudness - amplitude (30 - 100dB)
  – location (5° source & stream separation)
  – timbre - type of sound (lots of instruments)
• JND for sound is about 1 dB, 5-30Hz
• Whisper 20, Talking 50-70, Damage
  140dB
                                               13
Sound intensity vs. Frequency




                            14
                     Touch
• Three main sensations handled
  by different types of receptors:
   – Pressure (normal)
   – Intense pressure (pain)
   – Temperature (hot/cold)
• Sensitivity, Dexterity,
  Flexibility, Speed




                                     15
                                  Smell




Joseph Kaye, “Making scents: aromatic
output for HCI” ACM interactions Volume
10, Number 1 (2004), Pages 48-61          Solenoid-controlled scent bottles



                                                                              16
    Information Processing
• The Model Human Processor
  – Card, Moran and Newell, The Psychology
    of Human-Computer Interaction, Erlbaum,
    1983




                                              17
       MHP Block Diagram
               LONG-TERM MEMORY



           SHORT-TERM (WORKING) MEMORY

VISUAL IMAGE    AUDITORY IMAGE
    STORE           STORE




                      COGNITIVE            MOTOR
 PERCEPTUAL
                      PROCESSOR          PROCESSOR
  PROCESSOR

                                                     18
                 Properties
• Processors
  – cycle time, C
• Memories
  – Capacities
  – Decay




                              19
            Processors
• Perceptual Processor
  – C=100 ms (5-200)
  – Eye Movement (Saccade) 330ms (70-
    700ms)
• Cognitive Processor
  – C=70 (27-170ms)
• Motor Processing C=70ms (30-100ms)

                                        20
             Perceptual Stores
•   Impressions, not processing
•   Visual and auditory impressions
•   Very brief, but accurate representation
•   Decays quickly
    – (70 - 1000 ms visual; 0.9 - 3.5 sec auditory)
• Limited capacity
    – (7 - 17 letters visual; 4 - 6 auditory)


                                                      21
        Experiment…
L O B   R Q T Z W P




                      22
       Short-Term Memory
•   Small capacity, used for “calculations”
•   Decay occurs in a minute or less
•   Rehersal
•   Interference
•   5-9 Chunks
     • 4793619049 vs. 404 894 7328
     • NSAFBICIANASA vs. NSA FBI CIA NASA




                                              23
        Long term memory
• Large, persistent capacity, unknown
  limits
• Access times are slow and
  unpredictable

• Declarative vs. procedural


                                        24
                                  LONG-TERM MEMORY
                           R = Semantic + Visual + Auditory
                           D = Infinite
                           S = Infinite
                          SHORT-TERM (WORKING) MEMORY

          VISUAL IMAGE             AUDITORY IMAGE
              STORE                       STORE              R= Acoustic or Visual
        R = Visual                 R = Acoustic              D (1 chunk) = 73 [73-226] s
        D = 200 [70-1000] ms       D = 1.5 [0.9-3.5] s       D (3 chunks) = 7 [5-34] s
        S = 17 [7-17] letters      S = 5 [4.4-6.2] letters   S = 7 [5-9] chunks




           PERCEPTUAL                       COGNITIVE                         MOTOR
            PROCESSOR                       PROCESSOR                       PROCESSOR

          C = 100 [5-200] ms              C = 70 [27-170] ms             C = 70 [30-100] MS

R = Representation
D = Decay Time                  Eye movement (Saccade) = 230 [70-700] ms
S = Size                                                                                   25
C = Cycle Time [Range]
Another View




               26
     Recognition and Recall
• Recognition
  – Stimulus helps you retrieve
• Recall
  – Retrieval without a specific stimuli
• Implications for UIs?



                                           27
    Major Cognitive Processes
•   Selective Attention
•   Learning
•   Problem Solving
•   Language




                                28
         Problem Solving
• Reasoning
  – Deductive
  – Inductive
  – Abductive




                           29
             Deductive
• If A then B
• Derive logical conclusion from premise




                                           30
              Inductive
• Generalizing from cases seen before




                                        31
              Abductive
• Reason from facts to action that caused
  it




                                        32
         Models of Humans
• Stimulus-Response
  – Hick’s law
  – Practice law
  – Fitt’s law
• Cognitive Modeling (MHP)
  – Key-stroke Level Model
  – GOMS (and similar) Models
     • Higher-level (Goals, Operations, Methods, Selections)


                                                               33
               Hick’s Law
• Time to choose among n alternatives
  – T = Ic log2(n+1)
  – Ic ~ 150 msec
• Law of Large Menus




                                        34
      Power Law of Practice
• Tn = T1n-a
  – Tn to complete the nth trial is T1 on the first
    trial times n to the power -a; a is about .4,
    between .2 and .6
• Routine cognitive actions




                                                  35
     Keystroke-Level Model
            (KSLM)
• The Psychology of Human-Computer
  Interaction, Card, Moran and Newell,
  Erlbaum, 1983
• Assign times to basic human operations
• Calculate the efficiency of the UI
• Does anybody do this anymore?
  – Details follow if you care…

                                       36
          KSLM Components
•   Keystroking
•   Mouse button press
•   Pointing (typically with mouse)
•   Hand movement between keyboard and mouse
•   Drawing straight line segments
•   “Mental preparation”
•   System Response time



                                               37
      Step 1: MS Word “Find”
• Find Command to locate a six character word
  –   H (Home on mouse)
  –   P (Edit)
  –   B (click on mouse button - press/release)
  –   P (Find)
  –   B (click on mouse button)
  –   H (Home on keyboard)
  –   6K (Type six characters into Find dialogue box)
  –   K (Return key on dialogue box starts the find)

                                                        38
             Step 2: Add Ms
• Place M operators
• Rule 0a. In front of all K’s
   – NOT part of argument strings (not text or
     numbers)
• Rule 0b. In front of all P’s that select
  commands




                                                 39
    Rule 0b: P
                  H (Home on mouse)
selects command
                  MP (Edit)
                  B (click on mouse button)
    Rule 0b: P    MP (Find)
selects command
                  B (click on mouse button)
                  H (Home on keyboard)
                  6K (Type six characters)
   Rule 0a: K     MK (Return key on dialogue box
  is argument       starts the find)


                                               40
            Step 3: Remove Ms
• Remove M’s according to heuristic rules
    – Rules relate to chunking of actions
• Rule 1. Anticipated by prior operation
    – PMK ->PK (point and then click is a chunk)
• Rule 2. If string of MKs is a single cognitive unit (such as a
  command name), delete all but first
    – MKMKMK -> MKKK (same as M3K) (type “run rtn is a chunk)
• Rule 3. Redundant terminator, such as )) or rtn rtn
• Rule 4. If K terminates a constant string, such as command-rtn,
  then delete M
    – M2K(ls)MK(rtn) -> M2K(ls)K(rtn)
    – typing “ls” command in Unix followed by rtn is a chunk


                                                                   41
  Rule 1 delete M
  H anticipates P
                    H (Home on mouse)
                    MP (Edit)
                    B (click on mouse button)
Rule 1 delete M
H anticipates P     MP (Find)
                    B (click on mouse button)
                    H (Home on keyboard)
                    6K (Type six characters)
 Rule 4 Keep M      MK (Return key on dialogue box
                      starts the find)

                                                 42
    Step 4: Plug in Numbers
• Plug in real numbers from experiments
  – K: .08 sec for best typists, .28 average, 1.2 if
    unfamiliar with keyboard
  – B: down or up - 0.1 secs; click - 0.2 secs
  – P: 1.1 secs
  – H: 0.4 secs
  – M: 1.35 secs
  – R: depends on system; often less than .05 secs


                                                       43
         MS Word Find Results
H (Home on mouse)
P (Edit)
B (click on mouse button - press/release)
P (Find)
B (click on mouse button)
H (Home on keyboard)
6K (Type six characters into Find dialogue box)
MK (Return key on dialogue box starts the find)
• Timings
    – H = 0.40, P = 1.10, B = 0.20, M = 1.35, K = 0.28
    – 2H, 2P, 2B, 1M, 6K
• Predicted time = 6.43 secs

                                                         44

				
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posted:6/11/2011
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