Engineering Psychology PSY 378S

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Engineering PsychologyPSY 378S

• University of Toronto
• Spring 2006
• L15 Action Selection and RT

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Overview

• Stimulus-Response Compatibility
• Static and Dynamic Compatibilities
• Modality Compatibility

• Response Time
• Simple and Choice RT
• Hick-Hyman Law
• Speed-Accuracy Tradeoff
• Speed-Accuracy Operating Characteristic
• Processing Stages

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Simple Reaction Time

• In a simple reaction time (RT) situation, there
  is no uncertainty what the signal is, and there
  is no uncertainty how to respond
• Like sprinter in starting blocks

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Factors Affecting Simple Reaction Time

• 1) Stimulus Modality
• RT(aud) lt RT(vis)
• 2) Stimulus Intensity
• More intense stimuli lead to shorter RTs
• Can be modeled using SDT (aggregation of neural
  evidence over time)
• Can raise or lower criterion (e.g., false start
  for sprinter)

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Factors Affecting SimpleReaction Time

• 3) Temporal Uncertainty
• Greater uncertainty increases RT
• Greater warning interval increases RT
  (uncertainty in internal timing mechanism)
• But not too short
• Traffic lights short yellow light leads to high
  red light violation (Van der Horst, 1988)
• Increasing yellow light by 1 s reduced red light
  violation
• 4) Expectancy
• Within-Block effect
• Response after long wait faster than after short
• RT lower with greater expectancy

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Choice Reaction Time

• In a choice reaction time task, there can be more
  than one signal, and more than one type of
  response
• Each response corresponds to a signal

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Factors Affecting Choice RT

• Factors affecting simple RT also affect choice
• In choice RT situation, subject transmitting
  information from stimulus to response in
  information theory sense
• Hymans (1953) experiment
• S observes set of lights
• One light flashes
• S makes assigned response
• Number of lights (and responses) varied (N)
• Varying amount of information (H log2 N)
• Hick-Hyman Law
• Choice RT increases linearly with stimulus
  information
• RT a bHs

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Hick-Hyman Law
RT a bHs
N Number of Alternatives
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Information Transmission Rate

• Slope b is 170 ms/bitamount of extra time
  resulting from each added bit of stimulus
  information to be processed
• Can derive information transmission rate
  (bandwidth) by 1/b 0.00588 bits/ms 5.88
  bits/s
• Intercept a ( 180 ms) represents time to encode
  stimulus and execute response factors unrelated
  to stimulus information

RT a bHs
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H-H Law about Information

• What are three factors affecting amount of
  information?
• Number of alternatives, probability, context
• When probability or sequential constraints
  (context) varied to affect amount of information,
  H-H Law still holds
• Higher probability events lower total amount of
  stimulus information
• Mean RTs (averaging across lower and higher
  probability events) shortened

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Hick-Hyman Law
E1 Number of Alternatives E2 Probabilities E3
Context
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Hick-Hyman Law Robust

• Hick-Hyman Law tested many times with different
  kinds of stimuli and responses, and is generally
  accurate
• However, many other factors affect RTs

RT a bHs
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Problems for Hick-Hyman Law

• RT not just a function of number of bits
• Six variables that affect RT but not easily
  quantified using information theory
• Stimulus discriminability
• Repetition effect
• Response factors
• Practice
• Executive control
• S-R compatibility
• See text for details

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Speed-Accuracy Tradeoff

• Speed-Accuracy Tradeoff People tend to make more
  errors when they respond more rapidly if they
  take longer they tend to be more accurate
• A reciprocity between speed and error

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Optimal Information Transmission

• Constant bandwidth implied by H-H Law not quite
  accurate
• Rather there is one level of the S-A tradeoff
  that produces optimal performance
• Information transmission tends to be optimal at
  moderate speed-accuracy sets

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Pushing People along the Tradeoff

• When you push people to be extremely accurate,
  reaction time increases a lot for little increase
  in accuracydiminishing returns
• Effect of instructional manipulations depends on
  task difficulty (Howell Kreidler, 1963, 1964)
• To get most efficient performance
• For easy task, best to emphasize bandwidth
• For hard task, best to emphasize speed

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SAOC (Speed-Accuracy Operating Characteristic)

• Typically plotted as logP(correct)/P(error) vs.
  RT (Pew, 1969)
• Accuracy scale typically plotted in log units
• Tends to linearize the functions

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SAOC Space
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SAOC Performance Quality

• Northwest is best southeast is least good vs.
  poor performance
• analogous to d in SDT

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SAOC the Tradoff

• Going from southwest to northeastmoving along
  the SAOCrepresents different speed-accuracy
  tradeoff settings
• analogous to ? in SDT

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SAOC

• How could we change peoples settings
• payoffs, instructional strategies
• Or vary available equipment to perform task
• Keyboard arrangements (e.g., Dvorak vs. QWERTY)

http//www.mwbrooks.com/dvorak/
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SAOC hypothetical example

• Assume
• A Dvorak BQWERTY
• A is better than B across the range of
  speed-accuracy settings

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SAOC Slopes

• If however, slopes are different
• What is relative importance of speed vs.
  accuracy?

A
A Dvorak BQWERTY
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Auditory vs. Visual

• Other factors shift performance along the SAOC
• Auditory processing leads to more rapid,
  error-prone performance (quick and dirty) than
  visual

Visual
Auditory
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Stress

• High stress situations tend to move us to fast,
  inaccurate responding
• Regulations in the nuclear industry require
  workers to wait a certain amount of time before
  responding as a result

Lo Stress
Hi Stress
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Processing Stages
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Stages in Reaction Time

• Most information processing models generally
  assume that total RT equals sum of duration of
  number of component stages
• Do particular variables affect particular stages?
• Two general approaches
• Subtractive Method
• Additive Factors Technique

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Subtractive Method

• Donders (1869)
• Delete operation from one condition
• Compared simple vs. choice RT (assumed former has
  no response selection stage)
• Difference in RT between two conditions should
  represent time for response selection stage
• Problem Changing task may affect duration of
  first stage
• In choice RT, may encode stimulus differently
• Think of how you encode the stimulus when you
  only have to respond to one

Stimulus Encoding
Response Selection
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Additive Factors TechniqueSternberg (1969, 1975)

• Basic logic
• Manipulate two variables in factorial design
• If two factors affect common processing stage,
  produces statistical interaction
• If they affect different processing stages,
  produces two main effects

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Additive Factors Technique
Ctrl Hi Disc
N4
X
O
X
O
R
T
Disc Lo
S-R Compatibility
X
Y
X
O
R
T
Mask
O
X


Switch responses L/R
Task S classifies a single letter using a
particular response
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Additive Factors Technique
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Problems with Additive Factors

• Assumption that stages proceed strictly in series
  is wrong (McClelland, 1979 Meyer Kieras,
  1997a, 1997b)
• Overlap between stages (cascading processes)
• Process of preparation for response can proceed
  while stimulus still being perceived (Coles et
  al., 1988)

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Additive Factors Apps

• Nonetheless, additive factors useful
• How is speed of information processing influenced
  by different environmental and individual
  factors?
• Aging, drug and chemical effects, mental workload
• Workers exposed to chemicals in industrial
  environments
• Interaction between memory load and amount of
  mercury poisoning in bloodstream (Smith
  Langolf, 1981)
• Implied that toxins effect was localized at
  memory retrieval stage

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Break
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Stimulus-Response Compatibility

• Compatibility between displayed information and
  method of response or control
• Static sense Compatibility between a display
  location and the location of the response
• Dynamic sense Compatibility between display
  movement and movement involved in the response

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Locational Compatibility

• We naturally orient towards and move to source of
  stimulation in environment
• Infants will orient toand try to touchnew faces
  or pictures
• So why not put the control and the display in the
  same location? colocation principle
• touch screen, hypertext links, elevator buttons
• Cant always do that so, put controls right next
  to displays (as close as possible)

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Stovetops Revisited

• More compatible mappings in (a) means fewer
  mental operations (spatial transformations) from
  stimulus (stove burner arrangement) to response
  (select control)
• Norman called these natural mappings

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Cheating Colocation

• Can colocate controls and burners by connecting
  themmaking them a single object

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Principle of Congruence

• When cant follow the colocation principle, can
  get away with congruence
• Spatial array of controls is congruent with the
  spatial array of objects being controlled (stove
  burners)

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Testing the Congruence Principle(Fitts and
Seeger, 1953)

• Best performance for each stimulus array obtained
  from spatially congruent response array

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Compatibility Advantage Holds Up With Training
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Principle of Congruence

• Stimulus display garage doors (left and right)
• Response buttons (left and right)

Door 2
Door 1
Door 2
Door 1
To House
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Rules

• If congruence cannot be achieved, can use simple
  rule to map stimuli and responses
• Fitts and Deininger (1954)
• Used a circular array of 8 lights and 8 controls
• Used 3 mappings congruent, L/R reversed, and
  random
• Congruent better than reversed but reversed
  better than random
• Simple rule could be used to do the reversal!

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Design Solution Cant

• Put slight cant or angling of one array in
  direction congruent with the other
• Can be as fast as parallel arrangement

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Movement Compatibility

• Compatibility in dynamic sense
• Compatibility between display movement and
  movement involved in response
• Typically movement of control should correspond
  to movement in display

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Movement Compatibility

• Sometimes movement compatibility cant be
  achieved for practical reasons
• There are common ways to show an increase move a
  control up, to the right, forward, or clockwise
• These types of common conventions are called
  population stereotypes

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Movement Proximity

• Place moving control close to moving display
• Principle of movement proximity

Better than
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Movement Proximity

• Can run into problem when moving control is
  placed close to moving display
• In (b) movement proximity violates movement
  compatibility

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Movement Proximity

• But can arrange so that movement proximity
  corresponds to movement compatibility (c)

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Organizing S-R Compatibility
S-R Compatibility
Dynamic
Static
Colocation (Locational Compatibility)
Movement Proximity
Movement Compatibility
Congruence
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Modality Compatibility

• S-R compatibility can also be affected by
  stimulus and response modality
• If stimulus is light, faster choice RT results
  for manual than voice response
• If stimulus is spoken digit, faster with naming
  than spatial pointing response

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Modality Compatibility
Stimulus
Light (Visual)
Heard Digit (Auditory)
?
Manual (Spatial)
Response
?
Voice (Verbal)
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General Summary

• Stimulus-Response Compatibility
• Static and Dynamic Compatibilities
• Modality Compatibility

• Response Time
• Hick-Hyman Law
• Speed-Accuracy Tradeoff
• Speed-Accuracy Operating Characteristic
• Processing Stages