Week 3.1: Stimulus Identification and Response Selection

Question 1

Human Information Processing

Answer 1

When discussing human information processing we take a black box approach
-Input -> processing -> output
-identify stimulus, assume processing, measure output

Cognitive neuroscience, a field that is concerned with processing
-processing phenomena are not directly observable

In the field of motor Behaviour a chronometric approach was adopted
-measuring timings between input and output and infer amount of processing that must take place

Question 2

Stages of Human Information Processing

Answer 2

1. Stimulus identification
2. Response selection
3. Response programming
   *translating stimulus into response to produce an output

Many different information processing activities take place during the RT period
-it is critical to have a well-designed experiment to use RT as a measure of
processing

One can usually infer that RT is related to the amount processing of a stimulus or
task
-as processing time increases, reaction time also increases-> there is a
positive correlation

Question 3

What is an Easy Measure of Processing

Answer 3

Simple reaction time: a task that involves reacting to one stimulus
-gives a measure of processing time
-correlated with age
-affected by fatigue, attention, sensory modality of the cue

Question 4

Serial vs. Parallel Processing

Answer 4

Parallel processing:
-overlapping processes
-two or more stages happening at once

Serial processing:
-processing and sequential steps

*with regard to human information processing:
-some steps can occur in parallel under certain conditions
-some steps must occur in sequence in certain conditions

Question 5

Stimulus Identification

Answer 5

First the individual must perceive the stimulus
-involves stimulus detection and then identification

The stimulus must be sensed and processed
-processed until it contacts memory
-some memorized aspect of its relevance is aroused
-there are many variables that can affect the stimulus identification stage

Question 6

Sensation vs. Perception

Answer 6

Sensation involves the activation of sensory receptors
-sensory receptors have a minimum amount of stimulation required to
detect a stimulus (ex. auditory decibels- can only hear at certain frequencies)
-can be affected by attention at both the behavioural and neural level

Perception involves interpreting those sensations
-involves the combination and integration of numerous sources of information to form a percept
-moving from sensation to perception is what we do

Question 7

Stimulus detection

Answer 7

Stimulus detection is affected by:
-stimulus clarity, stimulus intensity, sensory cue modality

Question 8

Response Selection

Answer 8

After the stimulus is detected, the actor must now decide what response to initiate
-move or not to move
-move high or move low
-block or cover

Experimentally, we can explain the relationship between the reaction time and the number of possible stimulus response alternatives
-Choice RT: a reaction time task where the participant is presented with more than one possible stimulus
and the required response is dependent on that stimulus

Question 9

Hick’s Law

Answer 9

The time it takes to make a response is related to the number of stimulus
response
-Hick’s law was based on an experiment by Hick and Hyman
-presented in increasing number of stimulus response pairs and measured RT

Choice RT increases nearly a constant amount when stimulus response alternatives
-log linear relationship
-the relationship between the choice RT and the logarithm of the number of stimulus response alternatives should be linear

Choice RT= a + b *log2(N)
a= y-intercept
b= slope

Question 10

Practical applications of Hick’s Law

Answer 10

Can use to increase or decrease response alternatives to try to increase or decrease RT

Question 11

Bits of Information

Answer 11

Log2 (N) = a bit of information
-The amount of information required to reduce uncertainty by half
-Least amount of binary decisions
-Bit = Binary Digit

Question 12

Hick’s Law: What is the y-intercept experimentally

Answer 12

Reaction time when number of stimulus responses is equal to zero (simple RT)

Question 13

Hick’s Law: what is the slope experimentally

Answer 13

Reaction time as you increase bits by one

Question 14

Donder’s subtractive method (Simple RT, Choice RT and Go/No Go)

Answer 14

Simple RT (a) - Response programming (RP)
-Raise right hand in response to Green go signal
-RT=250ms
*fastest

Choice RT (b) - stimulus identification (SI), response selection (RS), response programming (RP)
-raise right hand in response to Green go signal
-raise left hand in response to Blue go signal
-RT=300ms
*slowest

Go/No Go (c) - Stimulus identification (SI), response programming (RP)
-raise hand and response to Green go signal, stop and response to Red
stop signal
-RT=280ms

(go no go ) - (simple RT) = Stimulus identification

(choice RT) - (go no go) = Response selection

Question 15

Simple RT, Choice RT and Go/No Go (Donder’s Method)

Answer 15

Simple RT tasks: reacting to one stimulus with the same response
-Number of stimuli choices = 1
-Number of response choices = 1

Choice RT tasks: selecting the appropriate response for a given stimulus
-Number of stimuli choices = 2
-Number of response choices = 2

Go/No-Go tasks: reacting to one stimulus, and not reacting to another
-Number of stimuli choices = 2
-Number of response choices = 1

Question 16

Other factors affecting response selection

Answer 16

-Although the number of stimulus response alternatives affects response selection, features of the stimulus response relationship could also have an impact
-One prominent example is a stimulus response compatibility (the mapping of the response to the action)

Pioneering work on stimulus response compatibility was performed by Fitts & Seeger 1953

Question 17

Simon Effect

Answer 17

Irrelevant spatial features have effects on reaction
-Participants responded to auditory cues played in either the left ear or the right ear
-Had to press the right key when they heard the word
-Had to press the left key when they heard the word left

Compared responses of spatial compatible trials versus incompatible trials

Has been replicated with numerous types of Trials

Question 18

Joint-Simon Effect (Sebanz et al., 2003)

Answer 18

Previous research has also suggested that we can co-represent actions
-when two people perform the Simon task, they perform similar to when performing a two-choice task

If you have a two Choice reaction time pass, when blue is presented on the right side it is a compatible stimulus but if the green is on the right side it is an incompatible stimulus
-compatible with stimulus spatially matched to the response, incompatible when the stimulus maps to the other side of the response, neutral and stimulator are presented in the middle

Question 19

Sebanz 2003

Answer 19

Joint Simon Effect:
-Participants responded faster and compatible versus non-compatible trials in the two Choice condition
-When performing the task with another person, participants also showed faster responses in the compatible compared to incompatible conditions
(result was found even though participants were instructed to respond to one colour)
-in the individual go no go task there were no differences between compatible and incompatible stimuli

Question 20

Practice Question: Considering Hick’s Law, how much more information in bits is required to increase RT by empirical constant b?

Answer 20

1 bit (b is the slope in Hick’s Law)