Demonstrates the Simon effect: even when stimulus location is irrelevant to the task, responses are faster and more accurate when the stimulus appears on the same side as the required response (congruent) than on the opposite side (incongruent).
Participants identify the colour of a square (red or green) regardless of where it appears on screen (left or right).
Fixation cross → Coloured square → Response → ITI
500 ms until response key press 500 ms
| Key | Meaning |
|---|---|
F |
Red |
J |
Green |
sudo apt install libsdl3-dev on Ubuntu/Debian)# Fullscreen, participant 1
go run main.go -s 1
# Windowed (development / testing)
go run main.go -s 1 -d
| Flag | Default | Description |
|---|---|---|
-s |
0 |
Participant ID (integer) |
-d |
off | Development mode: windowed 1024×768 |
Data are saved to goxpy_data/ as a .xpd file (CSV with a metadata header). One row per trial:
| Column | Description |
|---|---|
trial |
Trial number |
color |
Stimulus colour (red / green) |
position |
Stimulus position (left / right) |
key |
Key pressed |
rt |
Reaction time in milliseconds |
correct |
Whether the response was correct |
congruency |
congruent or incongruent |
Simon, J. R. (1969). Reactions toward the source of stimulation. Journal of Experimental Psychology, 81(1), 174–176. https://doi.org/10.1037/h0027448