Monetary Incentive Delay (MID) Task – PsyFlow Version

This task implements a classical Monetary Incentive Delay (MID) paradigm, designed to measure reward anticipation and outcome processing under different motivational conditions. It is built using the PsyFlow framework.

Task Overview

Participants are instructed to respond as quickly and accurately as possible to a briefly presented target after a cue and anticipation phase. Each cue indicates the condition: potential reward ("win"), potential loss avoidance ("lose"), or neutral ("neut"). Feedback is given based on performance.

The task dynamically adjusts target duration to maintain a target hit rate (~66%) using an adaptive controller.

Task Flow

Step	Description
Instruction	A textbox (instruction_text) presents task instructions in Chinese. Participants press space bar to begin.
Cue	A visual shape (circle, square, or triangle) indicates the trial type (win, lose, neutral).
Anticipation	A fixation cross is displayed while participants prepare.
Target	A brief target appears; participants must press the specified key (down) as quickly as possible.
Feedback	Performance feedback is shown based on the hit/miss outcome.
ITI (Inter-Trial Interval)	A short blank screen is shown before the next trial.
Block Break	After each block, performance is summarized and participants rest.
Goodbye	Final thank-you and score display.

Configuration Summary

All key settings are stored in the config/config.yaml file.

Subject Info (subinfo_fields)

Participants are registered with:

• Subject ID (3-digit number from 101–999)
• Session Name (e.g., Practice, Experiment)
• Experimenter Name
• Gender (Male or Female)

Localizations for Chinese are defined via subinfo_mapping.

Window Settings (window)

• Resolution: 1920 × 1080
• Units: deg
• Fullscreen: True
• Monitor: testMonitor
• Background color: gray

Stimuli (stimuli)

Stimulus Name	Type	Description
fixation	text	Central fixation cross
*_cue	circle/rect/polygon	Visual cue for condition type (win/lose/neut)
*_target	circle/rect/polygon	Target stimulus for response
*_hit_feedback	textbox	Feedback for hit trials
*_miss_feedback	textbox	Feedback for miss trials
iti_stim	text	Blank screen during ITI
instruction_text	textbox	Pre-task instruction screen
instruction_image1/2	image	Optional instructional images
block_break	textbox	Mid-task break and feedback screen
good_bye	textbox	End of task message and final score

Timing (timing)

Phase	Duration
Cue	0.3 seconds
Anticipation	1.0–1.2 seconds (randomized)
Target	Adaptive (initial 0.3s, min 0.15s, max 0.5s)
Feedback	1 second
ITI	0.6–0.8 seconds (randomized)

Triggers (triggers)

The following event triggers are sent via TriggerSender:

Event	Codes
Win cue onset	10
Lose cue onset	20
Neut cue onset	30
Anticipation onset	11, 21, 31
Target onset	12, 22, 32
Hit feedback onset	13, 23, 33
Miss feedback onset	14, 24, 34
Key press detected	15, 25, 35
No response detected	16, 26, 36
Experiment start/end	98 / 99
Block start/end	100 / 101
Fixation onset	1

Triggers can be customized for synchronization with EEG, fMRI, or other acquisition systems.

Adaptive Controller (controller)

The MID task uses an adaptive staircase algorithm to maintain a target hit rate of 66%.

Parameter	Value
Initial Target Duration	0.3 seconds
Minimum Duration	0.15 seconds
Maximum Duration	0.5 seconds
Step Size	0.05 seconds
Target Accuracy	66%
Condition-Specific	True (tracks separately for win, lose, neut)

The controller updates target duration based on ongoing performance during each block.

Running the Task

python main.py