Stop-Signal Task (SST)

Field	Value
Name	Stop-Signal Task (SST)
Version	main (1.0)
URL / Repository	https://github.com/TaskBeacon/SST
Short Description	A response inhibition task measuring the ability to suppress prepotent motor responses
Created By	Zhipeng Cao (zhipeng30@foxmail.com)
Date Updated	2025/06/22
PsyFlow Version	0.1.0
PsychoPy Version	2025.1.1
Modality	Behavior/EEG
Language	Chinese
Voice Name	zh-CN-YunyangNeural

1. Task Overview

The Stop-Signal Task (SST) is a cognitive paradigm used to assess response inhibition—the ability to withhold an already-initiated action. In each trial, participants are instructed to respond to directional go stimuli (left or right arrows) by pressing the corresponding key. On a subset of trials, a red stop signal appears shortly after the go stimulus, indicating that the participant should inhibit their response. The delay between the go and stop signal (SSD) is adaptively adjusted to maintain a 50% stop success rate.

2. Task Flow

Block-Level Flow

Step	Description
Load Config	Load YAML configuration for subject, task, timing, stimuli, and controller
Collect Subject Info	Get subject ID, name, age, and gender
Setup Triggers	Initialize trigger sender (via loopback serial)
Initialize Window/Input	Set up PsychoPy window and keyboard
Load Stimuli	Load all visual/text stimuli, convert instructions to audio
Initialize Controller	Create SSD controller from config
Show Instructions	Display instruction text + voice before starting
Loop Over Blocks	For each of 3 blocks: run 70 trials with generated conditions
Compute Block Feedback	Show go hit rate and stop success rate per block
Show Goodbye	Final message after task completion
Save Data	Save full trial-level data to CSV
Close	Close serial connection and PsychoPy window

Trial-Level Flow

Step	Description
Fixation	Present fixation cross for 0.8–1.0s with trigger
Go Only Trial	Present arrow; wait up to 1s for correct keypress; show feedback if none
Stop Trial	Present arrow for SSD duration; then switch to red stop signal
Response Recording	Capture whether responses occurred before or after stop signal
Adaptive Update	Adjust SSD based on stop success/failure

Controller Logic

Feature	Description
Type	1-up/1-down staircase adjusting stop-signal delay (SSD)
Target Success Rate	50%
Step Size	±0.05s
Range	0.05–0.5s
Condition Pooling	Shared SSD across conditions
Logging	Logs SSD adjustment and performance to PsychoPy console

3. Configuration Summary

a. Subject Info

Field	Meaning
subject_id	Unique participant number (101–999)
subname	Participant name (pinyin)
age	Age (5–60)
gender	Gender (Male or Female)

b. Window Settings

Parameter	Value
size	[1920, 1080]
units	deg
screen	1
bg_color	gray
fullscreen	True
monitor_width_cm	60
monitor_distance_cm	72

c. Stimuli

Name	Type	Description
fixation	text	White cross “+”
go_left	shape	White left-pointing arrow
go_right	shape	White right-pointing arrow
stop_left	shape	Red left-pointing arrow
stop_right	shape	Red right-pointing arrow
no_response_feedback	text	Message shown if participant fails to respond
block_break	text	Inter-block feedback with hit/stop accuracy
instruction_text	textbox	Full task instructions with keys and stop rule
good_bye	textbox	Final screen thanking participant

d. Timing

Phase	Duration (s)
fixation	random 0.8–1.0
go stimulus (max duration)	1.0
stop signal delay (SSD)	adaptive (0.05–0.5)
no-response feedback	0.8

e. Triggers

Event	Code
exp_onset	98
exp_end	99
block_onset	100
block_end	101
fixation_onset	1
go_onset	10
go_response	11
go_miss	12
pre_stop_response	23
on_stop_response	24
post_stop_response	25
no_response_feedback_onset	30

f. Adaptive Controller

Parameter	Value
initial_ssd	0.25
min_ssd	0.05
max_ssd	0.5
step	0.05
target_success	0.5
condition_specific	False
enable_logging	True

4. Methods (for academic publication)

Participants completed a stop-signal task (SST) designed to evaluate response inhibition. The task consisted of 3 blocks, each containing 70 trials, resulting in a total of 210 trials. On each trial, participants saw a directional arrow (left or right) and were instructed to press the corresponding key—“F” for left, “J” for right—as quickly and accurately as possible. On 25% of the trials, the arrow changed color (white to red) shortly after its onset, signaling the participant to inhibit their response. The delay between the go stimulus and the stop signal—the stop-signal delay (SSD)—was controlled adaptively using a 1-up/1-down staircase procedure. The SSD increased after successful inhibition and decreased after failed inhibition, with a target success rate of 50%.Trials began with a fixation cross (0.8–1.0s), followed by a go arrow. On go trials, the arrow remained on screen for up to 1 second or until a keypress. If no response occurred, a warning message was presented. On stop trials, the red stop signal replaced the arrow after an SSD-determined delay. Responses were recorded for both go and stop phases. The SSD was adjusted per trial based on inhibition performance. Participants received a break after each block, displaying their hit rate on go trials and success rate on stop trials.

5. References

Kok, A., Ramautar, J. R., De Ruiter, M. B., Band, G. P., & Ridderinkhof, K. R. (2004). ERP components associated with successful and unsuccessful stopping in a stop‐signal task. Psychophysiology, 41(1), 9-20.

Casey, B. J., Cannonier, T., Conley, M. I., Cohen, A. O., Barch, D. M., Heitzeg, M. M., … & Dale, A. M. (2018). The adolescent brain cognitive development (ABCD) study: imaging acquisition across 21 sites. Developmental cognitive neuroscience, 32, 43-54.