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Delayed Reward Task
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Script Author: David Nitz (nitz.david@gmail.com) for Millisecond Software, LLC.
last updated: 05-30-2023 by K. Borchert (katjab@millisecond.com) for Millisecond Software, LLC
Script Copyright © 05-30-2023 Millisecond Software
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BACKGROUND INFO
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The Delayed Reward Task by Cherek et al (1997) is a 2-choice procedure for assessing tolerance
for delayed rewards. It can be used as a measure of impulsivity.
Cherek, D. R., Moeller, F. G., Dougherty, D. M., & Rhoades, H.(1997). Studies of violent and
nonviolent male parolees: II. Laboratory and psychometric measurements of impulsivity.
Biological Psychiatry, 41, 523-529.
Related references:
Cherek, D. R., Moeller, F. G., Schnapp, W., & Dougherty, D. M. (1997). Studies of violent and
nonviolent male parolees: I. Laboratory and psychometric measurements of aggression.
Biological Psychiatry, 41, 514-522.
Moeller, F. G., Dougherty, D. M., Barratt, E. S., Oderinde, V., Mathias, C. W., Harper, R. A.,
& Swann, A. C. (2002). Increased impulsivity in cocaine dependent subjects independent of
antisocial personality disorder and aggression. Drug and Alcohol Dependence, 68, 105-111.
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TASK DESCRIPTION
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Participants get to choose between an A button (small with small, fixed delay)
or a B button (big with large, variable delay).
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DURATION
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the default set-up of the script takes appr. 18 minutes to complete
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DATA OUTPUT DICTIONARY
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The fields in the data files are:
(1) Raw data file: 'delayedrewardtask_cherek_raw*.iqdat' (a separate file for each participant)
build: The specific Inquisit version used (the 'build') that was run
computer.platform: the platform the script was run on (win/mac/ios/android)
date, time: date and time script was run
subject, group, with the current subject/groupnumber
session: with the current session id
blockCode, blockNum: the name and number of the current block (built-in Inquisit variable)
trialCode, trialNum: the name and number of the currently recorded trial (built-in Inquisit variable)
Note: trialNum is a built-in Inquisit variable; it counts all trials run; even those
that do not store data to the data file such as feedback trials. Thus, trialNum
may not reflect the number of main trials run per block.
nTrials: Number of trials (separate counts for training and test sessions).
response: Participant’s response (choice trials: A or B)
latency: latency for the current trial (in ms)
aDelay: Fixed delay in milliseconds for impulsive choices (option A). Default is 5000.
bDelay: Delay in milliseconds for controlled choices (option B) at the start of the session. Default is 15000. The delay is adjusted at runtime according to subjects' responses.
totalReward: Total amount of money rewarded (separate counts for training and test sessions).
impulsiveChoices: Running total of impulsive choices (applies to test sessions only).
controlledChoices: Running total of controlled choices (applies to test sessions only).
pctimpulsive: Proportion impulsive choices in test session
pctControlled: Proportion controlled choices in test session
(2) Summary data file: 'delayedrewardtask_cherek_summary*.iqdat' (a separate file for each participant)
inquisit.version: Inquisit version run
computer.platform: the platform the script was run on (win/mac/ios/android)
startDate: date script was run
startTime: time script was started
subjectId: assigned subject id number
groupId: assigned group id number
sessionId: assigned session id number
elapsedTime: time it took to run script (in ms); measured from onset to offset of script
completed: 0 = script was not completed (prematurely aborted);
1 = script was completed (all conditions run)
totalReward: Total amount of money rewarded (separate counts for training and test sessions).
impulsiveChoices: Running total of impulsive choices (applies to test sessions only).
controlledChoices: Running total of controlled choices (applies to test sessions only).
pctimpulsive: Proportion impulsive choices in test session
pctControlled: Proportion controlled choices in test session
meanDelaysControlled: the mean delay (in s) for choosing the delayed choice
Range: 7.333s (choosing only impulsive choice)- 30.5s (choosing only controlled choice)
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EXPERIMENTAL SET-UP
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During experimental sessions subjects were provided with two response options: 1) an
impulsive response option (option A); and 2) a self-control response option (option B).
Training Sessions:
At the beginning of the first session, subjects participated in a training session that consisted of 20
trials. During the first 10 trials the letter A was presented on the computer screen, and after
a 5-sec delay the letter A began to flash off and on. A single press of button A removed the
letter from the screen and added 5 cents to the counter (00.05). During the last 10 trials, the
letter B appeared, and 15 sec later the letter began to flash off and on. A single press of
button B removed the letter from the screen and added 15 cents to the counter (00.15). At
the end of the 20 training trials, the screen displayed "Training Over." The purpose of the
training sessions was to give subjects a brief exposure to the different monetary amounts and
delays associated with the letters A and B.
Test Sessions:
During these subsequent regular sessions, both the A and B letters appeared on the screen at
the beginning of each trial. The subject selected a letter by pressing the corresponding button,
either A or B. The selected letter remained on the screen, and the other letter disappeared.
After a delay, the letter began to flash off and on, and single response on that button added a
monetary value (either 5 or 15 cents) to the counter, and the letter disappeared.
The subsequent appearance of the two letters signaled the beginning of the next trial.
The letter A selection resulted in a 5-cent reward after a fixed delay of 5 sec.
The letter B selection resulted in a 15-cent reward after a delay that began each session at
15 sec. The delay for option B varied during the session. Each time the subject selected option
B, the next delay increased by 2 sec. Conversely, each time the subject selected option A, the
next delay for option B decreased by 2 sec. The delay for option B was never less than 7 sec,
and was thus always longer than the delay for option A, which was fixed at 5 sec. Since the
sessions were stopped after 60 trials, the length of the sessions varied depending upon the
choices of the subjects.
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INSTRUCTIONS
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see section Editable Instructions
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EDITABLE CODE
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check below for (relatively) easily editable parameters, stimuli, instructions etc.
Keep in mind that you can use this script as a template and therefore always "mess" with the entire code
to further customize your experiment.
The parameters you can change are:
skiptraining: Pseudo-boolean switch to (de-)activate the training block.
1 = no training block; 0 = run training block.
skiptest: Pseudo-boolean switch to (de-)activate the test block.
1 = no test block; 0 = run test block.
adelay: Fixed delay in milliseconds for impulsive choices (option A).
Default is 5000.
bdelay: Delay in milliseconds for controlled choices (option B) at the start
of the session. Default is 15000. The delay is adjusted at runtime
according to subjects' responses.
bdelaymin: Minimum value for the controlled choice delay. This value is used
in the runtime adjustments and should be greater than the fixed
impulsive choice delay ('parameters.adelay'). Default is 7000.
badjust: Amount in milliseconds by which the controlled choice delay is
adjusted. If subjects choose the 'controlled' option (B), the
controlled choice delay is increased by the value entered here.
If subjects choose the 'impulsive' option (A), the controlled choice
delay is decreased by the value entered here. Default is 2000.
areward: Fixed reward for impulsive choices. Default is 0.05.
breward: Fixed reward for controlled choices. Default is 0.15.
moneyUnit: by default, the money unit is in US "$"
position_moneyUnit: 0: the unit appears before the money amount (e.g. $15) (default)
1: the unit appears after the money amount (e.g. 15€)
