Task 1 Flashcards
Cognitive psychology
Study of mental activity as an info processing problem
- Assumption:
We don’t directly perceive & act in the world
-> Our perception, thoughts, actions depend on internal transformations or
computations
Tasks are composed of set of mental operations
-> Which involve taking representation as an input and performing some sort of process on it
-> Thus producing new representation or output
2 key underlying concepts
- Info processing depends on internal representations
- Mental representations undergo transformations
Example:
You first smell garlic bread (sensation) → You think about holiday in Italy at your grandmother’s house (perception) → You pick up the bread and eat it (action)
Reaction Time
The time between stimulus presentation and the response
Operation def. :
Participant intends to be as fast as possible w/out making errors
- Trials are repeated several dozen times
-> To get reliable mean RT (mRT)
-Observed average RT should gain validity as a measure of what we aim it to reflect
-> The minimum amount of time needed by participant to produce correct response
Theoretical assumption:
RT is minimum amount of time needed by pp to produce correct response
-> PP may try go be faster but will then find out that errors occur more often
-> PP can also be perfectly accurate if they take much longer time
- Instruction & training are to avoid that
Speed accuracy tradeoff
Tendency, when performing task, for either speed or accuracy to be sacrificed in order to prioritize the other
- The faster → the less accurate
-effects on mean RT should always be inspected in context of accuracy Neg. relationship btw RT & accuracy
->One way to investigate this: rune same task multiple times & give diff. speed-accuracy instruction every time
Outliers with RT
-Inattentiveness can cause large RT
- That skew the mean RT, standard deviation and variance
- Outliers can also be extremely fast responses
Dealing with outliers
Medians: The median is “robust measure of central tendency”
- Meaning it is relatively insensitive to outliers
Trimmed means:
-Middle nr. of trials
- Thus: it deletes upper & lower 50% of distribution
- One may delete smaller proportion (e.g. fastest & slowest 10%) & then take mean of remaining ones
Standard deviation:
- Compute mean & SD for each partic. & condition
- Then delete RTs that deviate more than some nr ‘C’ of SDs from mean
Fixed Criterion
-Delete all RTs exceeding some value and compute mean of rest
Doing nothing
-Own choice whether to remove or not & whether it would make sense
Instructions to participants
-Should be consistent
- Give feedback
- Experiments shouldn’t be too long
Subtraction method
- Construct 2 tasks that differ ony in single component
- Measure RT in both taks
- Subtract RT
- will give duration of single differing component
-Subtracting RT as RT(C)-RT(B) = duration of response selection
-Subtraction RT as RT(B)-RT(A) = duration of stimulus discrimination
Donders´3 tasks
-Task A: Simple RT
-> 1 possible stimulus and 1 possible response
-> sensory time + motor time
-Task B: 2-choice RT
-> 2 possible stimuli; each demand different response
-> sensory time + discrimination time + response selection time + motor time
-Task C: Go-nogo task/ disjunctive RT
-> 2 stimuli and 1 possible response
-> sensory time + discrimination time + motor time
Pure insertion
(assumption of Donder´s 3 task)
-Duration of all processing stages remains same when extra stage is added or removed
-Assumption implies no interactions among the cognitive components of a task
Seriality
(assumption of Donder´s 3 task)
Processing stages are carried out in a strictly serial manner
Only in the case that total RT is equal to sum of durations of individual stages
Aim of Sternberg´s additive factor method
- Identify whether stages are serial or parallel
- Controlling for limitations of Donder’s subtraction method
- Discover processing stages
Interaction
-Effect of one factor modulates the effect of another
-Simple effect of factor A varies across levels of factor B
Diffusion model
-Provide theory that explains distribution of RTs of both correct responses & errors in 2- choice RT task
Basic assumption:
-Info accumulates continuously during time btw stimulus onset & response Accumulated info is represented by internal counter
- Counter is driven in opposite directions
- By tiny bits of info → Supporting the different outcomes (correct vs. incorrect)
- Over time: counter runs in a corridor btw 2 thresholds - As soon as upper or lower threshold is hit
→ decision has been made & response A or B is executed
Random walk
The whole process of various trials can be simulated to obtain simulated RT distributions
- Can be tuned in a way that the simulated RT mimics the actually obtained RT
distributions closely
➔ If the match is close: Assumptions of the model are valid & parameters of diffusion model are
psychologically meaningful
Sternberg´s additive factor model
In each trial, a set of letters is presented and the participant has to memorize them
- This set can contain 1-6 letters
After these letters have been shown, a single ‘probe’ letter is presented and the participant has to say whether it was shown in the set of letters before or not → then he has to press ‘yes’ or ‘no’
=>RT increases linearly with the number of items held in memory
4 mental processes
1. Encode: the participant must identify the visible target
2. Compare: the participant must compare the mental representation of the target with
the representation of the the items in memory
3. Decide: the participant must decide whether the target matches one of the memorized
items
4. Respond: the participant must respond appropriately for the decision made in step 3
-> Factors that influenced one stage (e.g. stimulus intensity) would be additive with those that influenced another stage (e.g. motor output)
