Script Author: Katja Borchert, Ph.D. (katjab@millisecond.com), Millisecond
Created: September 22, 2015
Last Modified: March 27, 2026 by K. Borchert (katjab@millisecond.com), Millisecond
Script Copyright © Millisecond Software, LLC
This script implements a Probabilistic Reward Task, a simple categorization task using a differential reinforcement schedule of monetary reward. It can be used as a measure of reward responsiveness (hedonic capacity).
The setup of this script allows for absolute sizing of the stimuli. By default, the stimuli are NOT absolutely sized (the script uses the largest 4:3 portion of the current screen for data presentation). However, you can change the sizing parameter settings under section Defaults to turn on absolute sizing.
The implemented procedure is based on Pizzagalli et al (2005).
Pizzagalli, D.A., Jahn, A.L, & O'Shea, J.P. (2005). Toward an Objective Characterization of an Anhedonic Phenotype: A Signal-Detection Approach. Biol Psychiatry, 57(4), 319–327.
15 minutes
Participants are asked to categorize faces into "short" and "long" mouths. Correct responses are intermittedly rewarded with an asymmetric reinforcement schedule for short and long mouths. For half the participants short mouths get reinforced about 60% of the times ("frequent reward") whereas long mouths get reinforced only about 20% of the times ("infrequent reward"); for the other half of the participants the reverse is true.
Responsekeys are counterbalanced within groups. Assignment to the 4 experimental condition (2 reinforcement schedules x 2 response keys assignments) is done by groupnumber.
Face Stimuli are not original to Pizzagalli et al (2005). They can be edited under section Editable Stimuli.
(The default short mouth is about 88% of the long mouth).
Sizes of stimuli on screen are proportional to the monitor/canvas size;
Absolute Sizing can be turned on under section Defaults.
Instructions are not original to Pizzagalli et al (2005).
They can be edited in script probabilisticrewardtask_instructions_inc.iqjs
File Name: probabilisticrewardtask_summary*.iqdat
| Name | Description |
|---|---|
| inquisit.version | Inquisit version number |
| computer.platform | Device platform: win | mac |ios | android |
| computer.touch | 0 = device has no touchscreen capabilities; 1 = device has touchscreen capabilities |
| computer.hasKeyboard | 0 = no external keyboard detected; 1 = external keyboard detected |
| startDate | Date the session was run |
| startTime | Time the session was run |
| subjectId | Participant ID |
| groupId | Group number |
| sessionId | Session number |
| elapsedTime | Session duration in ms |
| completed | 0 = Test was not completed 1 = Test was completed |
| expGroup | 1 = short mouth is frequently rewarded 2 = long mouth is frequently rewarded |
| responseKeyAssignment | 1 = short mouth left/long mouth right 2 = short mouth right/long mouth left |
| countRewardTrials | Counts the number of rewards given out (across test blocks) |
| total | Stores the currently total cents won (across test blocks) |
Notes: Responses With Latencies < 150Ms Or Latencies > 2500Ms Removed From Summary Statistics |
|
| propCorrect | Overall proportion correct -across all test trials- |
| meanRT | Overall mean response latency (in ms) of correct responses - across all test trials |
| propCorrectFrequent | Proportion correct frequently rewarded mouth trials |
| meanRTFrequent | Mean latency (in ms) of correct frequently rewarded mouth trials |
| propCorrectInfrequent | Proportion correct infrequently rewarded mouth trials |
| meanRTInfrequent | Mean latency (in ms) of correct infrequently rewarded mouth trials |
Overall (And For Each Block) Measures Of Discriminability And Measures Of Response Bias |
|
| logD | Measure of Discriminability (see Pizzagalli et al, 2005, p.5), across all testblocks logD is a non-parameteric alternative measure to the traditional d' measure of a signal detection framework. |
| logB | Measure of Response Bias (see Pizzagalli et al, 2005, p.5), across all testblocks logB is non-parameteric alternative measure of the criterion measure of a signal detection framework |
File Name: probabilisticrewardtask_raw*.iqdat
| Name | Description |
|---|---|
| build | Inquisit version number |
| computer.platform | Device platform: win | mac |ios | android |
| computer.touch | 0 = device has no touchscreen capabilities; 1 = device has touchscreen capabilities |
| computer.hasKeyboard | 0 = no external keyboard detected; 1 = external keyboard detected |
| date | Date the session was run |
| time | Time the session was run |
| subject | Participant ID |
| group | Group number |
| session | Session number |
| blockcode | The name the current block (built-in Inquisit variable) |
| blocknum | The number of the current block (built-in Inquisit variable) |
| trialcode | The name of the currently recorded trial (built-in Inquisit variable) |
| trialnum | The number of the currently recorded trial (built-in Inquisit variable) trialnum is a built-in Inquisit variable; it counts all trials run even those that do not store data to the data file. |
| expGroup | 1 = short mouth is frequently rewarded 2 = long mouth is frequently rewarded |
| responseKeyAssignment | 1 = short mouth left/long mouth right 2 = short mouth right/long mouth left |
| blockCount | Counts the blocks |
| rewardShort | 0 = short mouth trial is not supposed to be rewarded 1 = short mouth trial is supposed to be rewarded (if response is correct; otherwise the next short trial that is correct is rewarded) |
| newRewardShort | 0 = no new reward_short (this happens if the last short mouth trial was supposed to be rewarded but response was incorrect) 1 = a new reward_short needs to be determined |
| rewardLong | 0 = long mouth trial is not supposed to be rewarded 1 = long mouth trial is supposed to be rewarded (if response is correct; otherwise the next log trial that is correct is rewarded) |
| newRewardLong | 0 = no new reward_long (this happens if the last long mouth trial was supposed to be rewarded but response was incorrect) 1 = a new reward_long needs to be determined |
| stimulusItem | The presented stimuli in order of trial presentation |
| image | The presented image |
| response | The scancode of the the participant's response key 18 = E 23 = I |
| responseText | The label of the response key |
| responseCat | The interpreted key response: "short" vs. "long" |
| correct | The correctness of the response (1 = correct; 0 = incorrect) |
| latency | The response latency (in ms); measured from onset of target |
| countRewardTrials | Counts the number of rewards given out (across test blocks) |
| total | Stores the currently total cents won (across test blocks) |
The procedure can be adjusted by setting the following parameters.
| Name | Description | Default |
|---|---|---|
Color Parameter |
||
| canvasColor | Display color of the actively used portion of the screen (the 'canvas') if set to a color other than the screenColor, the active canvas appears 'anchored' on the screen regardless of monitor size | white |
| screenColor | Color of the screen not used by the canvas ('inactive screen') | white |
| defaultTextColor | Default color of text items presented on active canvas | black |
| fixationHeight | The size of the fixation stim in % of canvas height | 10% |
| picSize | The size of the face images in % of canvas size | 80% |
| feedbackHeight | The size of the feedback stim in % of canvas size | 6% |
Timing Parameters |
||
| fixationDuration | The duration of the fixation stim in ms | 500 |
| signalDuration | The duration of the signal (face without mouth) before target appears in ms | 500 |
| targetDuration | The duration of the target (face with mouth) in ms | 100 |
| iti | The duration of the intertrial interval in ms | 0 |
| feedbackDuration | The duration of the feedback stim in ms | 1750 |
| restDuration | The duration of the rest trial inbetween blocks in ms | 30000 |
Outlier Removal |
||
| minLatency | Responses with reaction times (in ms) < 150ms are not considered for summary statistics | 150 |
| maxLatency | Responses with reaction times (in ms) > 2500ms are not considered for summary statistics | 2500 |
Reward |
||
| rewardAmount | The size of the reward in cents | 5 |
Responsekeys |
||
| responseKeyLeft | The left response key | "E" |
| responseKeyRight | The right response key | "I" |