Script Author: Meticulously handcrafted from the finest code by David Nitz (nitz.david@gmail.com), Millisecond.
Last Modified: January 04, 2025 by K. Borchert (katjab@millisecond.com), Millisecond
Script Copyright © Millisecond Software, LLC
This script implements a Delay and Probability Discounting Procedure to establish a) the hypothetical payoffs at which people start to discount higher monetary rewards in favor of shorter wait periods (Delay Discounting) b) the fictional payoffs at which people start to discount high monetary rewards of unsure events in favor of lower monetary rewards of sure wins (Probability Discounting)
The implemented procedure is based on Richards et al (1999).
Richards, J. B., Zhang, L., Mitchell, S. H., & De Wit, H. (1999). Delay or probability discounting in a model of impulsive behavior: Effect of alcohol. Journal of the Experimental Analysis of Behavior, 71(2), 121-143.
15 minutes
Participants choose between a standard amount of money ($10) with different time/probability delays or a variable amount with no delay until an indifference point for each delay is found or until the maximum number of trials has been run for each delay (default: 30).
• 5 temporal delays and 5 probability "delays"; tested within in a mixed design
temporal delays are 0, 2, 30, 180 and 365 days
probability delays are: 100, 90, 75, 50 and 25 percent
=> change delays under section EDITABLE PARAMETERS
• 1 standard amount (10), variable amounts between 0 <=variable amount <= 10
• once an indifference point is found for a particular delay, that delay is not run any further
• potentially 30 trials can be run for each delay -> can be edited under block.dpdt
• after a predetermined amount of trials (see EDITABLE PARAMETERS), a distractor trial is run after each test trial
• script stops if an indifference point has been found for all delays or the maximum number of trials
has been run for each delay (default: 30).
see section EDITABLE INSTRUCTIONS
File Name: dpdt_richards_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 |
| nips | The total number of successfully determined indifference points. The procedure determines a total of 10 different indifference points (for five temporal delays, 't1' to 't5', and five probabilistic 'delays', 'p1' to 'p5'). The procedure is stopped as soon as 'expressions.nips' returns 10, i.e. when all indifference points at question have been obtained. |
| t1IpFound | Value reflecting whether an indifference point has been successfully determined ('1') or not ('0') for temporal delay t1. |
| t1Ip | Obtained indifference point estimate for temporal delay t1 |
| t2IpFound | Value reflecting whether an indifference point has been successfully determined ('1') or not ('0') for temporal delay t2. |
| t2Ip | Obtained indifference point estimate for temporal delay t2 |
| t3IpFound | Value reflecting whether an indifference point has been successfully determined ('1') or not ('0') for temporal delay t3. |
| t3Ip | Obtained indifference point estimate for temporal delay t3 |
| t4IpFound | Value reflecting whether an indifference point has been successfully determined ('1') or not ('0') for temporal delay t4. |
| t4Ip | Obtained indifference point estimate for temporal delay t4 |
| t5IpFound | Value reflecting whether an indifference point has been successfully determined ('1') or not ('0') for temporal delay t5. |
| t5Ip | Obtained indifference point estimate for temporal delay t5 |
| p1IpFound | Value reflecting whether an indifference point has been successfully determined ('1') or not ('0') for probabilistic delay p1. |
| p1Ip | Obtained indifference point estimate for probabilistic ‘delay’ p1 |
| p2IpFound | Value reflecting whether an indifference point has been successfully determined ('1') or not ('0') for probabilistic delay p2. |
| p2Ip | Obtained indifference point estimate for probabilistic ‘delay’ p2 |
| p3IpFound | Value reflecting whether an indifference point has been successfully determined ('1') or not ('0') for probabilistic delay p3. |
| p3Ip | Obtained indifference point estimate for probabilistic ‘delay’ p3 |
| p4IpFound | Value reflecting whether an indifference point has been successfully determined ('1') or not ('0') for probabilistic delay p4. |
| p4Ip | Obtained indifference point estimate for probabilistic ‘delay’ p4 |
| p5IpFound | Value reflecting whether an indifference point has been successfully determined ('1') or not ('0') for probabilistic delay p5. |
| p5Ip | Obtained indifference point estimate for probabilistic ‘delay’ p5 |
| text.subjectQuestion.currentItem | The question that was randomly selected to determine participant’s reward |
| text.subjectAnswer.currentItem | The participant’s response to the win question |
File Name: dpdt_richards_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 cou |
| trialCount | Total number of trials run (including distractor trials). |
| latency | The participant’s response latency (in ms) for the current trial (in ms) |
| response | The selected response of the participant for the current trial (for most trials: A or B) |
| text.question.currentItem | The actual decision question presented to participant |
| questionType | 0 = temporal delay question; 1 = probabilistic delay question |
| text.subjectQuestion.currentItem | The question that was randomly selected to determine participant’s reward |
| text.subjectAnswer.currentItem | The participant’s response to the win question |
| var | 'Variable' amount of money offered in the current trial. This value is computed according to the proper bottom and top limits (see below) by expressions 't1Var' through 'p5Var'. |
| std | 'Standard' amount of money to use throughout the task. Default is 10. |
The Following Variable Is Only Relevant For Trials With Question Type = 1 |
|
| t | Value of the current temporal delay used in a given trial. |
The Following Variable Is Only Relevant For Trials With Question Type = 2 |
|
| p | Value of the current probabilistic 'delay' used in a given trial. |
The Following Variables Are Only Relevant For Trials Trialcode = “T1” (The Same Applies To All Temporal Delay Trials.T2-T5) |
|
| t1BMax | The respective maximum bottom limits for temporal delay t1. Used to determine the variable amount of money offered in a given t1 trial and to adjust the limits for subsequent t1 trials. |
| t1BMin | The respective minimum bottom limits for temporal delay t1. Used to determine the variable amount of money offered in a given t1 trial and to adjust the limits for subsequent t1 trials. |
| t1TMin | The respective minimum top limits for the temporal delay t1. Used to determine the variable amount of money offered in a given t1 trial and to adjust the limits for subsequent t1 trials. |
| t1TMax | The respective maximum top limits for the temporal delay t1. Used to determine the variable amount of money offered in a given t1 trial and to adjust the limits for subsequent t1 trials. |
| t1Var | 'variable' amount for temporal delays t1. The valid range is restricted by the respective maximum bottom and maximum top limits. Values returned lie between those limits in 0.5 increments. |
| t1Count | Number of trials for temporal delay t1. |
| t1IpFound | Value reflecting whether an indifference point has been successfully determined ('1') or not ('0') for temporal delay t1. |
| t1Ip | Obtained indifference point estimate for temporal delay t1 |
| parameters.t1 | Predetermined value for temporal delay t1 questions in this script (t1 = 0) |
The Following Variables Are Only Relevant For Trials Trialcode = “P1” (The Same Applies To All Probabilistic Delay Trials.P2-P5) |
|
| p1BMax | The respective maximum bottom limits for probabilistic ‘delay’ p1. Used to determine the variable amount of money offered in a given p1 trial and to adjust the limits for subsequent p1 trials. |
| p1BMin | The respective minimum bottom limits for probabilistic ‘delay’ p1. Used to determine the variable amount of money offered in a given p1 trial and to adjust the limits for subsequent p1 trials. |
| p1TMin | The respective minimum top limits for the probabilistic ‘delay’ p1. Used to determine the variable amount of money offered in a given p1 trial and to adjust the limits for subsequent p1 trials. |
| p1TMax | The respective maximum top limits for the probabilistic ‘delay’ p1. Used to determine the variable amount of money offered in a given p1 trial and to adjust the limits for subsequent p1 trials. |
| p1Var | 'variable' amount for probabilistic ‘delay’ p1. The valid range is restricted by the respective maximum bottom and maximum top limits. Values returned lie between those limits in 0.5 increments. |
| p1Count | Number of trials for probabilistic ‘delay’ p1. |
| p1IpFound | Value reflecting whether an indifference point has been successfully determined ('1') or not ('0') for probabilistic ‘delay’ p1. |
| p1Ip | Obtained indifference point estimate for probabilistic ‘delay’ p1 |
| p1 | Predetermined value for probabilistic ‘delay’ for p1-questions in this script (p1 = 100) |
Relevant For All Trials |
|
| nips | The total number of successfully determined indifference points. The procedure determines a total of 10 different indifference points (for five temporal delays, 't1' to 't5', and five probabilistic 'delays', 'p1' to 'p5'). The procedure is stopped as soon as 'expressions.nips' returns 10, i.e. when all indifference points at question have been obtained. |
| distractorStart | Number of trials to run *before* distractor trials should be added to the mix. Default is 70, i.e. after 70 experimental trials ('t1' to 'p5') have been run, every second trial will be a distractor trial ('d0'). |
| d0Count | Total number of distractor trials run |
| d0Var | Computes a random 'variable' amount to be used in distractor trials ('d0'). The value returned always lies between 0 and the defined 'standard' amount ($10) in 0.5 increments |
The procedure can be adjusted by setting the following parameters.
| Name | Description | Default |
|---|---|---|
| pretrialDelay | Adjustable pretrialpause in milliseconds. Change as needed. | 500 |
| posttrialDelay | Adjustable posttrialpause in milliseconds. Change as needed. | 0 |
| distractorStart | Number of trials to run *before* distractor trials should be added to the mix. Default is 70, i.e. after 70 experimental trials ('t1' to 'p5') have been run, every second trial will be a distractor trial ('d0'). | 70 |
| std | 'Standard' amount of money to use throughout the task. | 10 |
5 Temporal Delays |
||
| t1 | Temporal delay t1 (in days) | 0 |
| t2 | Temporal delay t2 (in days) | 2 |
| t3 | Temporal delay t3 (in days) | 30 |
| t4 | Temporal delay t4 (in days) | 180 |
| t5 | Temporal delay t5 (in days) | 365 |
5 Probabilistic 'Delays' |
||
| p1 | Probabilistic 'delay' p1 (in percent) | 100 |
| p2 | Probabilistic 'delay' p2 (in percent) | 90 |
| p3 | Probabilistic 'delay' p3 (in percent) | 75 |
| p4 | Probabilistic 'delay' p4 (in percent) | 50 |
| p5 | Probabilistic 'delay' p5 (in percent) | 25 |