Lecture 18 - Decision Making

Question 1

Decisional Processes

Answer 1

Input, sensory
output, motor command afferent based on choices made.

Question 2

Take home message

Answer 2

The speed that we select and
initiate actions depends on the number of alternatives and the compatibility between the stimuli and response

Question 3

Three stages of information processing

Answer 3

1. Stimulus identification (perception)
   -what and where
   Sensory of visual, audio, touch, smell
2. Response selection (Decision)
   - decide and planning based on environment and goal
3. Response Programming (Action)
   -program and act

Question 4

Reaction, movement and response time

Answer 4

Reaction time: is the difference in time between stimulus presentation and the initiation of the motor response (processing speed)

Movement time: time elapsed from
end of reaction time to the completion of movement

Response time: Time elapsed between
stimulus presentation and end of
movement (RT + MT)

Question 5

Simple reaction time

Answer 5

Time interval between the presentation of a known stimulus and
the motor response

On your mark…Set…GO!: The starter’s pistol is the stimulus that
triggers the motor response

MOST TIME IS SPENT IN STIMULUS IDENTIFICATION PHASE

Simple reaction time is when stimulus is knows in advance

One stimulus and one response

Question 6

Choice reaction time

Answer 6

Time interval between the presentation of one of several possible stimuli and the beginning of one of several
potential motor responses

Ex: deer runs in front of car

Stimulus identification: Detect deer’s position, speed. Oncoming traffic? Traffic behind you? Car’s speed? Weather and road conditions

Response selection: Brake, swerve (left or right?), continue driving

Requires time to detect and
identify stimulus, then select,
plan and initiate a response

Equal time in all phases

Several stimuli, several responses (slower then SRT)

Question 7

Hicks Law - The # of Choices Influences RT

Answer 7

Hick discovered the relation between # of choices and RT could be described by a simple log-linear equation

Hick’s Law: RT = a(log2(n)) + b

where:
n = # of S-R alternatives

a = slope: the slope (term a in equation) is the expected increase in RT when the # of S-R alternatives is doubled

b = y-intercept: the y-intercept ( the term b in equation) is the expected RT when no choice is required

Question 8

Stimulus Response (S-R) compatibility

Answer 8

Spatial Comp: Stove example

Example A is easier to use due to spatial mapping between burners and
control dials

Hypothesis: people respond more slowly in spatially-
incompatible trials

Other examples: Movement compatibility

The movement of displays and controls
relative to the response of the system being displayed or controlled

The turn signals in a car align with the
rotation of the steering wheel – CCW
for left and CW for right