Stroop Task

Field	Value
Name	Stroop Task
Version	main (1.0)
URL / Repository	https://github.com/TaskBeacon/Stroop
Short Description	A task measuring response inhibition and selective attention.
Created By	Zhipeng Cao (zhipeng30@foxmail.com)
Date Updated	2025/07/24
PsyFlow Version	0.1.0
PsychoPy Version	2025.1.1
Modality	Behavior/EEG
Language	Chinese
Voice Name	zh-CN-YunyangNeural

1. Task Overview

The Stroop Task is a classic experimental paradigm used to assess selective attention and response inhibition. Participants are presented with a word (a color name) printed in a specific ink color. They are instructed to name the ink color of the word, ignoring the word itself. The task measures how efficiently a participant can focus on a target attribute (the ink color) and filter out distracting information (the word’s meaning).

2. Task Flow

Block-Level Flow

Step	Description
Load Config	Load task configuration from config.yaml.
Collect Subject Info	Display a form to collect participant demographics.
Setup Triggers	Initialize the trigger sender for EEG/fMRI synchronization.
Initialize Window/Input	Create the PsychoPy window and keyboard handler.
Load Stimuli	Load all visual stimuli defined in the config using StimBank.
Show Instructions	Present task instructions to the participant.
Loop Over Blocks	For each block: run trials, then compute and show block-level feedback.
Show Goodbye	Display a final thank you message.
Save Data	Save all recorded trial data to a CSV file.
Close	Close the trigger port and quit PsychoPy.

Trial-Level Flow

Step	Description
Fixation	Show a central fixation cross (+).
Stimulus	Present the Stroop stimulus (e.g., the word “Red” in green ink).
Response	Record the participant’s key press (f for red, j for green).
Feedback	Display feedback (Correct, Incorrect, or No Response).
ITI	A blank screen shown for a random duration before the next trial.

3. Configuration Summary

a. Subject Info

Field	Meaning
subject_id	Unique participant ID (3 digits).
subname	Participant’s name (Pinyin).
age	Participant’s age.
gender	Participant’s gender.

b. Window Settings

Standard PsychoPy window settings for fullscreen display.

c. Stimuli

Name	Type	Description
fixation	text	Central cross +.
congruent_red	text	The word “红” (Red) in red ink.
congruent_green	text	The word “绿” (Green) in green ink.
incongruent_red	text	The word “绿” (Green) in red ink.
incongruent_green	text	The word “红” (Red) in green ink.
correct_feedback	textbox	“正确” (Correct) in white.
incorrect_feedback	textbox	“错误” (Incorrect) in white.
no_response_feedback	textbox	“未反应” (No Response) in white.
instruction_text	textbox	Instructions explaining the task.
block_break	text	Inter-block message showing accuracy.
good_bye	text	Final thank you message.

d. Timing

Phase	Duration (s)	Config Variable
fixation	0.5	fixation_duration
stimulus	2.0 (max response time)	stim_duration
feedback	0.5	feedback_duration
iti	random 0.8–1.2	iti_duration

e. Triggers

Event	Code
exp_onset	98
exp_end	99
block_onset	100
block_end	101
fixation_onset	1
congruent_stim_onset	10
incongruent_stim_onset	20
red_key_press	30
green_key_press	31
feedback_correct_response	51
feedback_incorrect_response	52
feedback_no_response	53
feedback_onset	60

4. Methods (for academic publication)

In this experiment, participants performed a Stroop task to assess selective attention and response inhibition. Each trial began with a central fixation cross, displayed for 500 ms. Subsequently, a word was presented in the center of the screen for up to 2000 ms or until a response was made. Participants were instructed to respond to the ink color of the word while ignoring the word’s meaning by pressing the ‘f’ key for red ink or the ‘j’ key for green ink. Following their response, feedback was provided for 500 ms, indicating whether the response was correct, incorrect, or if no response was made.

The task included two types of stimuli: congruent trials, where the word and ink color matched (e.g., the word “Red” in red ink), and incongruent trials, where the word and ink color were mismatched (e.g., the word “Red” in green ink). These conditions were presented in a randomized order within each block.

The task was structured into 3 blocks of 60 trials each (total 180 trials), with equal numbers of each condition (congruent-red, congruent-green, incongruent-red, incongruent-green) in each block. After each block, participants received feedback on their accuracy and were given the opportunity to rest before continuing to the next block. The inter-trial interval varied randomly between 800 and 1200 ms to prevent anticipatory responses.

This design allows for the examination of cognitive control processes, specifically the ability to selectively attend to relevant information while suppressing interference from irrelevant information. The difference in performance (reaction time and accuracy) between congruent and incongruent trials provides a measure of the “Stroop effect,” which reflects the cost of inhibiting conflicting information.

5. References

1. Stroop, J. R. (1935). Studies of interference in serial verbal reactions. Journal of Experimental Psychology, 18(6), 643-662.

2. MacLeod, C. M. (1991). Half a century of research on the Stroop effect: An integrative review. Psychological Bulletin, 109(2), 163-203.