Last Modified: January 22, 2025 by K. Borchert (katjab@millisecond.com), Millisecond
Script Copyright © Millisecond Software, LLC
This script implements a version of the classic Stroop Task with keyboard input. The classic Stroop paradigm demonstrates the interference of word meaning on the naming of the color in which the words are written as measured by reaction time/accuracy differences to color-meaning congruent and color-meaning incongruent combinations.
Stroop, J, R. (1935). Studies of interference in serial verbal reactions. Journal of Experimental Psychology, 18, 643-662.
2 minutes
Participants are given color words written in color and are asked to indicate the color of the word (not its meaning) by key press as fast as they can without making too many errors. Congruent trials: color word and the color it is presented in are the same Incongruent trials: color word and the color it is presented in are not the same Control trials: colored rectangles
1 Testblock with:
• 4 colors (red, green, blue, black) x 3 color-stim congruency (congruent, incongruent, control) x 7 repetitions = 84 trials
• trials are randomly sampled
Trial Timing:
- stimuli stay on screen until response (latencies are measured from onset of stimuli)
- intertrial interval of 200ms
- error feedback of 400ms
congruent/incongruent: color words
control: rectangle shapes
see "stroopwithcontrolkeyboard_instructions_inc.iqjs"
Instructions are not original to the task. They are provided by Millisecond.
See "stroopwithcontrolkeyboard_instructions_inc.iqjs"
File Name: stroopwithcontrolkeyboard_summary*.iqdat
| Name | Description |
|---|---|
| inquisit.version | Inquisit version number |
| computer.platform | Device platform: win | mac |ios | android |
| startDate | Date the session was run |
| startTime | Time the session was run |
| subjectId | Participant ID |
| groupId | Group number |
| sessionId | Session number |
| elapsedTime | Session duration in ms |
| completed | 0 = Test was not completed 1 = Test was completed |
| propCorrect | Overall proportion correct of all trials |
| meanRT | Overall mean latency (in ms) of all correct trials |
| propCorrectCongruent | Proportion correct of congruent trials |
| propCorrectIncongruent | Proportion correct of all incongruent trials |
| propCorrectControl | Proportion correct of all control trials |
| meanRTCorrCongruent | Mean latency of all correct congruent trials (in ms) |
| meanRTCorrIncongruent | Mean latency of all correct incongruent trials (in ms) |
| meanRTCorrControl | Mean latency of all correct control trials (in ms) |
Stroop Effects |
|
| stroopAccuracy | Difference in proportion corrects for (Congruent-Incongruent) => positive difference: participants were more accurate on categorizing congruent stims than on incongruent ones |
| stroopLatency | Difference in meanCorrRT for (Incongruent - Congruent) => positive difference: participants were on average faster on correctly categorizing congruent stims than on incongruent ones |
| stroopInhibitionAccuracy | Difference in proportion corrects for (Control - Incongruent) => positive difference: participants were more accurate on categorizing control stims than on incongruent ones (this performance difference ~ cost of inhibiting the dominant response) |
| stroopInhibitionLatency | Difference in meanCorrRT for (Incongruent - Control) => positive Difference: participants were on average faster on correctly categorizing control stims than on incongruent ones (this latency difference ~ cost of inhibiting the dominant response) |
File Name: stroopwithcontrolkeyboard_raw*.iqdat
| Name | Description |
|---|---|
| build | Inquisit version number |
| computer.platform | Device platform: win | mac |ios | android |
| date | Date the session was run |
| time | Time the session was run |
| subject | Participant ID |
| group | Group number |
| session | Session number |
| blockCode | Name of the current block |
| blockNum | Number of the current block |
| trialCode | Name of the current trial |
| trialNum | Number of the current trial |
| congruency | 1 = congruent (color of word and meaning of word are the same) 2 = incongruent (color of word and meaning of word are different) 3 = control (rectangles) |
| stimulusItem | The presented words |
| response | The participant's response (scancode of response button) 32 = D (red) 33 = F (green) 36 = J (blue) 37 = K (black) |
| responseCategory | The interpreted key response "red" "green" "blue" "green" |
| correct | The correctness of the response (1 = correct; 0 = incorrect) |
| latency | The response latency (in ms); measured from onset of word |
| congruentCorrect | Number of correct congruent responses |
| incongruentCorrect | Number of correct incongruent responses |
The procedure can be adjusted by setting the following parameters.
| Name | Description | Default |
|---|---|---|
| keyRed | The red response button | 32 -> d |
| keyGreen | The green response button | 33 -> f |
| keyBlue | The blue response button | 36 -> j |
| keyBlack | The black response button | 37 -> k |