Script Author: David Nitz, Millisecond
Last Modified: January 26, 2025 by K. Borchert (katjab@millisecond.com), Millisecond
Script Copyright © Millisecond Software, LLC
This script implements the Money/Food Delay Discounting Task, an adjusting delay discounting task to assess the reward amounts at which people start to discount higher monetary/food rewards in favor of shorter wait periods.
The implemented procedure is based on:
Odum, A.L., Baumann, A.A.L., Rimington, D.D. (2006). Discounting of delayed hypothetical money and food: Effects of amount. Behavioural Processes, 73, 278-284.
15 minutes
Participants are asked to select btw. 2 options: one option presents a higher value but with a delay (7 different ones), the second option presents a lower value but with an immediate pay-off. The lower value continuously decreases or increases (decrease/increase tested in blocked format). The options tested are 'Money' and 'Food'.
2 options (food, money: tested in blocked format) x 2 orders (ascending, descending: tested in blocked, consecutive format) x 7 delays (tested in blocked format, in ascending order);
tested within subjects
4 different experimental groups (assignment by groupnumber)
1: Money-> Food, desc -> asc
2: Money-> Food, asc -> desc
3: Food -> Money, desc -> asc
4: Food -> Money, asc -> desc
Indifference Point Calculations:
For each of the 7 temporal delays 2 indifference points are assessed: one for ascending order and one for descending order.
Indifference points are reached when participants switches response pattern 'consistently':
-> descending order: after 2 choices of the delayed option
-> ascending order: after 2 choices of the immediate option
The final indifference point for a delay is the midpoint of these 2.
see section EDITABLE STIMULI
see section EDITABLE INSTRUCTIONS
File Name: ddt_moneyfood_summary*.iqdat
| Name | Description |
|---|---|
| inquisit.version | Inquisit version number |
| computer.platform | Device platform: win | mac |ios | android |
| 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 |
| parameters.delayedReward | The set amount for a delayed reward ($10) ipDelay1M- |
| ipDelay7F | The IPs for the 7 different delays for food (F) and money (M) blocks |
File Name: ddt_moneyfood_raw*.iqdat
| Name | Description |
|---|---|
| build | Inquisit version number |
| computer.platform | Device platform: win | mac |ios | android |
| date | Date the session was run |
| time | Time the session was run |
| subject | Participant ID |
| group | Group number |
| session | Session number |
| blockCode | Name of the current block |
| blockNum | Number of the current block |
| trialCode | Name of the current trial |
| trialNum | Number of the current trial |
| blockCount | The number of blocks run |
| blockType | Type of current block: “money” or “food” |
| order | Current order of values "descending" vs “ascending” |
| trialCount | DiscountTrials run in the current block |
| response | Participant’s response (choice trials: ‘delayed’ or ‘immediate’) |
| latency | Response latency for the current trial in ms |
| delay | The currently selected delay |
| parameters.delayedReward | The set amount for a delayed reward ($10) |
| immediateReward | The currently selected immediate reward |
| delayedResponseStreak | Tracks the number of consecutive delayed responses per block |
| immediateResponseStreak | Tracks the number of consecutive immediate responses per block |
| ipDesc | The indifference point found in the descending blocks of a consecutive pair of money/food blocks for a given delay |
| ipAsc | The indifference point found in the ascending blocks of a consecutive pair of money/food blocks for a given delay |
| ip | The overall estimated indifference point of a pair of money/food blocks: average of the ip_asc and ip_desc of a consecutive pair of money/food blocks for a given delay |
The procedure can be adjusted by setting the following parameters.
| Name | Description | Default |
|---|---|---|
| pretrialdelay | Pretrialpause | 0ms |
| posttrialdelay | Posttrialpause | 500ms |
| delayedreward | The default value to use for the delayed reward (here: $10.00) | |
| delay1:- | ||
| delay7 | The proposed 7 delays tested (defaults: "1 day", "2 days", "1 week", "2 weeks", "1 month", "6 months", "2 years") |