Experiential Discounting Task

Script Author: Katja Borchert, Ph.D. (katjab@millisecond.com), Millisecond

Created: January 06, 2013

Last Modified: January 26, 2025 by K. Borchert (katjab@millisecond.com), Millisecond

Script Copyright © Millisecond Software, LLC

Background

This script implements the Experiential Discounting Task, a type of Delay Discounting task that assesses the degree to which the subjective value of a commodity decreases as a function of a delay. In contrast to more traditional Delay Discounting Tasks, the Experientiel Discounting Task provides participants with actual experiences of delays as consequences of their choices.

The implemented procedure is based on:

Reynolds, B. & Schiffbauer, R. (2004). Measuring state changes in human delay discounting: an experiential discounting task. Behavioural Processes, 67, 343–356.

And:

Smits,R.R, Stein,J.S., Johnson, P.S., Odum, A.L., & Madden, G.J. (2013). Test–Retest Reliability and Construct Validity of the Experiential Discounting Task. Experimental and Clinical Psychopharmacology, 21, 155–163.

Millisecond thanks Dr. Fillmore and Nicholas Van Dyke for collaborating on this script. Millisecond further thanks Dr. Madden for answering procedural questions pertaining to the EDT.

Duration

30 minutes

Description

The goal of the game is to win as much money as one can. In order to win money, participants choose between 2 options: the Standard option (on the right) and the Adjust option (on the left). When choosing the Standard option participants can win a fixed amount of money (higher than with the adjust option) but it is more uncertain whether they will win it (probabilistic reward, default probability p = 0.35) and they may have to wait to find out whether or not they won (4 different delay periods). With the Adjust option, participants can immediately add the advertised amount of money to their winnings. Choosing the Standard option will increase the amount that can be won with the Adjust option for the next round (up to a point); choosing the Adjust option will decrease the amount that can be won with the Adjust option for the next round. After choosing the same option consecutively for 4 (default) times in a row, participants will be forced to choose the opposite option. Forced trials in this script do not influence the amount that can be won with the adjust options. The game is over if either an Indifference Point for the two options can be determined or a predetermined time period has passed.

Procedure

• 2 choices: standard vs. adjust (NO choice is given if the same option was chosen 4 times in a row => forced choice)
• 4 delay periods: 0, 7s, 14s, 28s (Smits et al, 2013; editable parameters); tested in blocked format
• The 4 delay periods are run in sequence of ascending delays (Smits et al, 2013)
-> more info under section EXPERIMENT
• win probability: p = 0.35, fixed (can be edited under EDITABLE CODE -> Editable Lists)
• Standard Option: set win amount of $0.30 (does not change)
• Adjust Option: start win amount of $0.15; can increase (up to 24 cents) or decrease (down to 6cents) depending on selected option

(1) 'Adjust Win Amount' Adjustment Rules:
Selecting the Standard Choice will increase the Adjust Win Amount, selecting the Adjust Choice will
decrease the Adjust Win Amount
• The INITIAL change amount to increase or decrease is calculated as follows: change = round(0.15*original Adjust Amount) = round(0.15*0.15) = round(0.0225) = 0.02
• If the same choice is made consecutively, 0.15 is reduced consecutively by 0.02 until it reaches 0.03, after that it changes to 0.02 and stays there
=> Example: Participant chooses Standard Option 4 times in a row
1. change = round(0.15*0.15) = 0.02 (Adjust Amount = 0.15 + 0.02 = 0.17; after choosing Standard option, participant could now add 17 cents to winnings when choosing Adjust option next)
2. change = round(0.13*0.15) = 0.02 (Adjust Amount = 0.17 + 0.02 = 0.19)
3. change = round (0.11*0.15) = 0.02 (Adjust Amount = 0.19 + 0.02 = 0.21)
4. change = round (0.09*0.15) = 0.01 (Adjust Amount = 0.21 + 0.01 = 0.22)
(forced)
5. change = round (0.07*0.15) = 0.01 (Adjust Amount = 0.22 + 0.01 = 0.23)
6. change = round (0.05*0.15) = 0.01 (Adjust Amount = 0.23 + 0.01 = 0.24)
7. change = round (0.03*0.15) = 0.00 (Adjust Amount = 0.24 + 0.00 = 0.24)
8. change = round (0.02*0.15) = 0.00 (Adjust Amount = 0.24 + 0.00 = 0.24)
(forced)

• Choosing the opposite option will undo the previous adjustments in the reversed order*
example: if participant were now to choose the Adjust Option for 8 times in a row the Adjust Amount would change
1. 0.24 - 0.00 = 0.24
2. 0.24 - 0.00 = 0.24
3. 0.24 - 0.01 = 0.23
4. 0.23 - 0.01 = 0.22
(forced standard)
5. 0.22 - 0.01 = 0.21
6. 0.21 - 0.02 = 0.19
7. 0.19 - 0.02 = 0.17
8. 0.17 - 0.02 = 0.15
=> back to start conditions

• this script offers the option to set via parameters.reversaloption whether to
a) reverse in the exact same order (that is if participant has reached parameters.min_adjustvalue (0.02)- and
continues with same choice the reversal would take into account how many times participant was at 0.02)
example: 0.15, 0.13, 0.11, 0.09, 0.07, 0.05, 0.03, 0.02, 0.02, 0.02
reversal: 0.02, 0.02, 0.02, 0.03, 0.05, 0.07, 0.09, 0.11, 0.13, 0.15
b) reverse in the same order but start reversing immediately after participant reaches values.minadjustvalue (0.02)
(reversal starts with 0.03 regardless how many times participants had chosen a particular button with
with values.adjustamount = 0.02)
example: 0.15, 0.13, 0.11, 0.09, 0.07, 0.05, 0.03, 0.02, 0.02, 0.02
reversal: 0.03, 0.05, 0.07, 0.09, 0.11, 0.13, 0.15

(2) Indifference Point
After 16 mandatory choice trials (default), the program checks whether the Indifference Point can be determined.
The Indifference Point can be determined if participant chose the same number of Adjust and Standard options for the last
6 choice trials. If this condition is met, the Indifference Point = average of the last 6 adjust amounts.
If this condition is not met, the block continues and the program checks after each new choice trial if the
Indifference condition is met at this point (or if predetermined time for block has expired, see (3)).

(3) Duration of Game/Block
• at least 16 (default) choice trials per game/block
• Game/block quits if
a) the participant chose the same number of Standard options as Adjust options during the last 6 rounds => Indifference Point
can be established (see above)
b) the predetermined time for the game/block is up.

Determination of Predetermined Time:
• The predetermined time of a block = 20 (standard option trials) * values.delay
=> each block allows the selection of 20 choice standard option trials
(!!! for values.delay = 0; the predetermined time of a block = 20 and not 0 to allow for the selection
of 20 choice standard option trials)
• The game duration decreases by values.delay in trial.delayinterval_standard for choice standard option trials only
• if the game ends before predetermined time is up (because IP has been found) the remaining time is added to an interblock trial
(trial.interblockinterval) can be turned off via Editable parameter

in the unlikely even that participant chooses only Adjust option, an endless loop is created.
For this particular reason, the script has
- an emergency block termination duration which is 15 minutes long (editable parameter) does require some block responding to kick in
- a built-in time to abort the script after 2h (editable parameter) will abort after 2h whether any responses are made or not

Stimuli

provided by Millisecond - can be edited under section Editable Stimuli

Instructions

Instructions are not original to the task. They are provided by Millisecond
and can be edited under section Editable Instructions

Original instructions from Reynolds & Schiffbauer (2004) are provided under section Editable Instructions
for comparisons.

Summary Data

File Name: experientialdiscountingtask_summary*.iqdat

Data Fields

Raw Data

File Name: experientialdiscountingtask_raw*.iqdat

Data Fields

Parameters

The procedure can be adjusted by setting the following parameters.