Delay Discounting Task with Money and Food

Technical Manual

Script Author: David Nitz, Millisecond

Last Modified: January 09, 2026 by K. Borchert (katjab@millisecond.com), Millisecond

Background

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 et al (2006).

References

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.

Duration

15 minutes

Description

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'.

Procedure

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.

Stimuli

see section EDITABLE STIMULI in script 'ddt_moneyfood_instructions_inc.iqjs'

Instructions

see section EDITABLE INSTRUCTIONS in script 'ddt_moneyfood_instructions_inc.iqjs'

Summary Data

File Name: ddt_moneyfood_summary*.iqdat

Data Fields

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
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-ipDelay7M	The indifference points for the 7 different delays for Money (M)
ipDelay1F-ipDelay7F	The indifference points for the 7 different delays for Food (F)

Raw Data

File Name: ddt_moneyfood_raw*.iqdat

Data Fields

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.
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

Parameters

The procedure can be adjusted by setting the following parameters.

Name	Description	Default
Design
delayedReward	The default value to use for the delayed reward (here: $10.00)	10.00
Timing Parameters
pretrialDelay	Pretrialpause (in ms) in choice trial	0
posttrialDelay	Posttrialpause (in ms) in choice trial	500
Delays: Edit The 7 Delays In Language-Dependent Script 'Ddt_Moneyfood_Instructions_Inc.Iqjs'

Delay Discounting Task with Money and Food

Technical Manual

Background

References

Duration

Description

Procedure

Indifference Point Calculations:

Stimuli

Instructions

Summary Data

Data Fields

Raw Data

Data Fields

Parameters

Design

Timing Parameters

Delays: Edit The 7 Delays In Language-Dependent Script 'Ddt_Moneyfood_Instructions_Inc.Iqjs'