Monetary Incentive Delay (MID) Task

Field	Value
Name	Monetary Incentive Delay (MID) Task
Version	main (1.0)
URL / Repository	https://github.com/TaskBeacon/MID
Short Description	A task measuring reward anticipation and feedback processing using adaptive timing
Created By	Zhipeng Cao (zhipeng30@foxmail.com)
Date Updated	2025/06/21
PsyFlow Version	0.1.0
PsychoPy Version	2025.1.1
Modality	Behavior/EEG

1. Task Overview

The Monetary Incentive Delay (MID) Task is designed to assess reward processing and motivational control. Participants respond to brief target stimuli that follow cues indicating potential monetary gain, loss, or neutral outcomes. By analyzing reaction times and success rates, the task evaluates anticipatory and feedback-related cognitive processes. An adaptive timing algorithm adjusts target durations based on participant performance, maintaining consistent task difficulty.

2. Task Flow

Block-Level Flow

Step	Description
Load Config	Load task configuration and subject form
Collect Subject Info	Collect demographic/subject info using SubInfo form
Setup Triggers	Initialize trigger sender using serial port (COM3)
Initialize Window/Input	Create PsychoPy window and keyboard handler
Load Stimuli	Load all stimuli via StimBank, convert instructions to voice, preload
Setup Controller	Create adaptive controller from config
Show Instructions	Present text and voice instruction before starting
Loop Over Blocks	For each block: countdown, run 60 trials, compute and show block feedback
Show Goodbye	Present final feedback with total score
Save Data	Save all trial data to CSV
Close	Close serial port and quit PsychoPy

Trial-Level Flow

Step	Description
Cue	Show condition-specific cue (win/lose/neutral) with trigger
Anticipation	Display fixation; allow response (early keypress logged)
Target	Show target with adaptive duration; record response
Pre-feedback Fixation	Display fixation before feedback
Feedback	Present hit/miss feedback based on performance
Adaptive Update	Update target duration based on hit/miss outcome

Controller Logic

Feature	Description
Adaptive Duration	Target duration adjusts between 0.04 and 0.37 seconds
Step Size	±0.03 seconds
Accuracy Target	66% accuracy threshold
Condition Specific	Tracks performance separately by condition (win/lose/neutral)
Logging	Performance logs are printed to PsychoPy console

3. Configuration Summary

a. Subject Info

Field	Meaning
subject_id	Unique participant number (101–999, 3 digits)
subname	Participant name (pinyin)
age	Participant age (5–60)
gender	Participant gender (Male/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	Central cross "+"
win_cue	circle	Magenta circle (reward)
lose_cue	rect	Yellow square (punishment)
neut_cue	triangle	Cyan triangle (neutral)
win_target	circle	Black circle target
lose_target	rect	Black square target
neut_target	triangle	Black triangle target
win_hit_feedback	textbox	“击中 +10 分” (black text, SimHei)
win_miss_feedback	textbox	“未击中 +0 分”
lose_hit_feedback	textbox	“击中 -0 分”
lose_miss_feedback	textbox	“未击中 -10 分”
neut_hit_feedback	textbox	“击中 +0 分”
neut_miss_feedback	textbox	“未击中 -0 分”
instruction_text	textbox	Multi-line Chinese instructions (includes scoring rules)
block_break	text	Inter-block message showing block, accuracy, and score
good_bye	text	End screen showing final score

d. Timing

Phase	Duration (s)
cue	0.3
anticipation	random 1.0–1.2
target	adaptive (0.04–0.37)
prefeedback fixation	random 0.6–0.8
feedback	1.0

e. Triggers

Event	Code
exp_onset	98
exp_end	99
block_onset	100
block_end	101
win_cue_onset	10
win_anti_onset	11
win_target_onset	12
win_hit_fb_onset	13
win_miss_fb_onset	14
win_key_press	15
win_no_response	16
lose_cue_onset	20
lose_anti_onset	21
lose_target_onset	22
lose_hit_fb_onset	23
lose_miss_fb_onset	24
lose_key_press	25
lose_no_response	26
neut_cue_onset	30
neut_anti_onset	31
neut_target_onset	32
neut_hit_fb_onset	33
neut_miss_fb_onset	34
neut_key_press	35
neut_no_response	36
fixation_onset	1

f. Adaptive Controller

Parameter	Value
initial_duration	0.2
min_duration	0.04
max_duration	0.37
step	0.03
target_accuracy	0.66
condition_specific	true

4. Methods

Participants performed a computerized Monetary Incentive Delay (MID) task to assess motivational processing under different reward contingencies. The task consisted of 3 blocks, each comprising 60 trials, totaling 180 trials. Each trial began with a cue, a colored shape (circle, square, or triangle), signaling whether the trial was a reward, punishment, or neutral condition. Following a variable anticipation phase (1.0–1.2 s), a black target appeared briefly. Participants were instructed to press the spacebar as quickly as possible upon target onset.

The target's presentation duration was controlled by an adaptive algorithm that updated the duration after each trial based on performance. Initial target duration was set to 0.2 s and was adjusted between 0.04 and 0.37 s using ±0.03 s increments to stabilize performance at a target accuracy of 66%, tracked separately by condition.

Feedback followed the target phase, based on whether participants responded within the target duration. “击中” (“hit”) and “未击中” (“miss”) messages were shown with point gain/loss specific to the cue type. After each block, a break screen summarized the participant's accuracy and cumulative score. The task began with audio-visual instructions and ended with a final message displaying total score.

5. References

The task is originally developed by Knutson 2000:

Knutson, B., Westdorp, A., Kaiser, E., & Hommer, D. (2000). FMRI visualization of brain activity during a monetary incentive delay task. Neuroimage, 12(1), 20-27.

Here, we adopted the ABCD Study design of the task:

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.