Script Author: Katja Borchert, Ph.D. (katjab@millisecond.com), Millisecond
Created: January 06, 2018
Last Modified: January 12, 2026 by K. Borchert (katjab@millisecond.com), Millisecond
Script Copyright © Millisecond Software, LLC
This script implements the Minute Discounting Task; a quick procedure to estimate delay discount rates of monetary rewards. Instead of adjusting the amounts and keeping delay intervals constant, the Minute Discounting Tasks adjusts the delays.
The implemented procedure is described in Koffarnus & Bickel (2014).
Koffarnus, M.N. & and Bickel, W.K (2014). A 5-Trial Adjusting Delay Discounting Task: Accurate Discount Rates in Less Than One Minute. Experimental and Clinical Psychopharmacology, 22, 222–228.
1 minute
Participants receive 5 questions that ask whether they prefer a smaller amount (default: $5) now or a larger amount (default: S10) at variable delays (delays depend on previous choices). The task takes about a minute. The discount rate k is calculated.
1 Test block with 5 choice trials
• each trial presents a choice between the immediate amount and the delayed amount
=> based on response the new delay gets selected for the next trial based on
adjusting the index of the selected delays (see item.delayChoices under section STIMULUS)
• delay parameters used in this script to calculate the discount rate k are published in: Koffarnus & Bickel (2014, Table 1, p.224)
Adjustment Rule of the indices:
• the first delay always uses index = 16 ("3 weeks")
• the index adjustment value starts at 16/2=8 and is halved for each new trial (8, 4, 2, 1)
• if the immediate amount is selected: the index is adjusted down by the current adjustment value
• if the delayed amount is selected: the index is adjusted up by the current adjustment value
Example:
• the index adjust amount in trial 1 = 8:
if the immediate amount is selected in trial 1 (index always 16), trial 2 presents the delay for index 8 (16-8) ("1 day")
if the delayed amount is selected in trial 1 (index always 16), trial 2 presents the delay for index 24 (16 + 8) ("2 years")
• the index adjust amount in trial 2 = 4:
if the immediate amount is selected in trial 2 (e.g. index 8), trial 3 presents the delay for index 4 (8-4)("4 hours")
if the delayed amount is selected in trial 2 (e.g. index 8), trial 3 presents the delay for index 12 (8 + 4)("4 days")
etc.
provided by Millisecond - can be edited in script minutediscountingtask_instructions_inc.iqjs
File Name: minutediscounting_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 |
Parameter Values |
|
| immediateAmount | The promised immediate amount (default: $5) |
| delayedAmount | The promised delayed amount (default: $10) |
Performance Metrics |
|
| ed50 | Stores the estimated ED50 (in days) ~ the number of days that a delay is tolerated to receive the higher payoff Effective Delay 50% (ED50): can be directly translated into k-values |
| k | Main DV = stores the absolute k-value (discount rate, inverse of ED50) The higher the discount rate, the less participant is willing to wait for the delayed higher reward and the more the lesser, immediate reward is preferred. |
| meanRT | The mean choice reaction time (measured from onset of the response buttons) |
File Name: minutediscounting_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. |
Parameter Values |
|
| immediateAmount | The promised immediate amount (default: $5) |
| delayedAmount | The promised delayed amount (default: $10) |
Performance Metrics |
|
| trialCount | A running count of the choice trials run |
| choiceNo | Stores the current choice trial number (1-5) attached to the current index (should always be equal to the number of choice trials run = values.trialCount) |
| index | The index of the current choice values (choice trial #1 starts with index = 16) |
| indexAdjustment | The current index adjustment value |
| delayChoice | The variable delay choice assigned to the current index |
| response | The participant's response: selected response button "now" vs. "delayed" |
| latency | The response latency (in ms); measured from: onset of response buttons |
| ed50 | Stores the estimated ED50 (in days) ~ the number of days that a delay is tolerated to receive the higher payoff Effective Delay 50% (ED50): can be directly translated into k-values |
| k | Main DV = stores the absolute k-value (discount rate, inverse of ED50) The higher the discount rate, the less participant is willing to wait for the delayed higher reward and the more the lesser, immediate reward is preferred. |
The procedure can be adjusted by setting the following parameters.
| Name | Description | Default |
|---|---|---|
Design |
||
| delayedAmount | The promised delayed amount | 10 |
| immediateAmount | The promised immediate amount | 5 |
Timing Parameters |
||
| iti | The intertrial interval between each choice trial the options are blacked out during the iti | 500 |