Last Modified: August 06, 2026 by K. Borchert (katjab@millisecond.com), Millisecond
Script Copyright © Millisecond Software, LLC
This script implements a simple visual Simon Task, a measure of visuospatial attention and inhibitory control processes. The classic Simon Effects refers to the observation of stimulus-response compatibility: stimuli congruent in spatial location and response button location (e.g. stimulus presented on the left screen and response button is located on the left side) elicit faster responding than stimuli incongruent in spatial location and response button location (e.g. stimulus presented on the left screen and response button is located on the right side).
The implemented procedure is based on the description in Bialystok et al (2004).
Bialystok, E., Craik, F. I. M., Klein, R., & Viswanathan, M. (2004). Bilingualism, Aging, and Cognitive Control: Evidence From the Simon Task. Psychology and Aging, 19(2), 290-303.
2 minutes
Brief overview taken from Bialystok et al., 2004, p. 292 (slightly adapted):
Each trial begins with a fixation cross in the center of the screen that remains visible for 800 ms and is followed by a 250-ms blank interval. At the end of this interval, a red or blue square appears on either the left or the right side of the screen and remains on the screen for 1,000 ms if there is no response. Participants are instructed to press the left 'A' key when they see a blue square and the right 'L' key when they see a red square. Response timing begins with the onset of the stimulus, and the response terminates the stimulus. There is a 500-ms blank interval before the onset of the next trial.
The experiment begins with eight practice trials, and participants must complete all eight trials success-
fully to proceed to the experimental trials. If a mistake is made, participants are given additional
pratice trials until all eight trials are completed without error.
The following 28 experimental trials, half of which present the square on the same side as the associ-
ated response key (congruent trials) and half of which present the square on the opposite side
(incongruent trials), are presented in a randomized order.
red and blue square - size can be controlled via parameters.squaresize under section Editable Parameters
Instructions are not original to the task. They are provided by Millisecond
as htm/html pages and simple page elements and can be edited either by changing
the provided htm/html files or directly under Editable Instructions.
To edit htm/html-files: open the respective documents in simple Text Editors such as TextEdit (Mac)
or Notepad (Windows).
The instruction code can be found in script "visualsimontask_instructions_inc.iqjs"
File Name: visualsimontask_summary*.iqdat
| Name | Description |
|---|---|
| startDate | Date the session was run |
| startTime | Time the session was run |
| subjectId | Participant ID |
| groupId | Group number |
| sessionId | Session number |
| inquisit.version | Inquisit version number |
| computer.platform | Device platform: win | mac |ios | android |
| computer.touch | 0 = device has no touchscreen capabilities; 1 = device has touchscreen capabilities |
| computer.hasKeyboard | 0 = no external keyboard detected; 1 = external keyboard detected |
| elapsedTime | Session duration in ms |
| completed | 0 = Test was not completed 1 = Test was completed |
| propCorrect | Proportion correct across all test trials |
| meanRT | Mean latency of correct test trials in ms |
| propCorrectCongruent | Proportion correct of congruent test trials |
| meanRTCongruent | Mean latency of correct congruent test trials in ms |
| propCorrectIncongruent | Proportion correct of incongruent test trials |
| meanRTIncongruent | Mean latency of correct incongruent test trials in ms |
Speed-Accuracy Trade Off: Linear Integrated Speed-Accuracy Score, Lisas ("Error-Corrected Processing Speed" In Ms) |
|
| sdRTPooled | The pooled standard deviation of correct response times across all test trials |
| errorSDPooled | The pooled standard deviation of error rates across all test trials |
| lisasCongruent | LISAS score for Congruent trials |
| lisasIncongruent | LISAS score for Incongruent trials |
Simon Bias Scores Based On: Accuracy, Response Times, And Lisas |
|
| simonEffectAcc | Difference in proportions correct "[congruent] - [incongruent]" positive value: participants made more errors on incongruent than on congruent trials |
| simonEffectRT | Ms difference in "[mean corrRT Incongruent] - [mean corrRT Congruent]" positive value: participants responded faster on congruent than on incongruent trials |
| simonEffectLisas | Difference in LISAS scores ("error-corrected processing speed") from Incongruent and Congruent Trials (lisasIncongruent - lisasCongruent) => integration of response time and accuracy in one measure => positive difference, "error-corrected processing speed" was faster for Congruent than for Incongruent ones => a positive difference supports that processing Incongruent trials required more cognitive effort, time, or accuracy sacrifices than processing congruent trials |
File Name: visualsimontask_raw.iqdat
| Name | Description |
|---|---|
| date | Date the session was run |
| time | Time the session was run |
| subject | Participant ID |
| group | Group number |
| session | Session number |
| build | Inquisit version number |
| computer.platform | Device platform: win | mac |ios | android |
| computer.touch | 0 = device has no touchscreen capabilities; 1 = device has touchscreen capabilities |
| computer.hasKeyboard | 0 = no external keyboard detected; 1 = external keyboard detected |
| blockcode | The name the current block (built-in Inquisit variable) |
| blocknum | The number of the current block (built-in Inquisit variable) |
| trialcode | The name of the currently recorded trial (built-in Inquisit variable) |
| trialnum | The number of the currently recorded trial (built-in Inquisit variable) trialnum is a built-in Inquisit variable; it counts all trials run even those that do not store data to the data file. |
| countTrials | Trial count (resets after each practice session) |
| congruence | Congruent (stim position and response button position on the same side) vs. incongruent |
| stimhpos | Left vs. right (the position of the stimulus on the screen) |
| stimType | Blue Square vs. Red Square |
| response | The participant's response (scancode of response key) 30 = 'A' key 38 = 'L' key |
| responseText | The label of the response button |
| respLocation | Left vs. right (the interpreted key response, 30 => left; 38 => right) |
| correct | The correctness of the response (1 = correct; 0 = incorrect) |
| latency | The response latency in ms; measured from onset of stimulus |
The procedure can be adjusted by setting the following parameters.
| Name | Description | Default |
|---|---|---|
Timing Parameters |
||
| fixationCrossDuration | The duration of the fixation cross in ms | 800 |
| isi | The interstimulus interval between fixation cross and square in ms | 250 |
| responseWindow | The responsewindow/duration of square in ms | 1000 |
| iti | The intertrial interval in ms | 500 |
Sizing/Location Parameters |
||
| squareSize | The square size in % of canvas height | 25% |
| leftX | The left square coordinate in % of screen canvas | 15% |
| rightX | The left square coordinate in % of screen canvas | 85% |
Response Keys |
||
| responseKeyBlueLeft | The left response button for a blue square | "A" |
| responseKeyredRight | The right response button for a red square | "L" |