Effort Expenditure for Reward Task

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

Created: January 28, 2015

Last Modified: January 09, 2023 by K. Borchert (katjab@millisecond.com), Millisecond

Script Copyright © Millisecond Software, LLC

Background

This script implements the Effort Expenditure for Rewards Task; a measure of reward motivation. The implemented procedure is based on:

Treadway MT, Buckholtz JW, Schwartzman AN, Lambert WE, Zald DH (2009) Worth the ‘EEfRT’? The Effort Expenditure for Rewards Task as an Objective Measure of Motivation and Anhedonia. PLoS ONE 4(8): e6598. doi:10.1371/journal.pone.0006598

Duration

23 minutes

Description

Participants have to select between an Easy and a Hard task. Both tasks involve pressing the Spacebar for a predetermined amount of time. The Hard task offers more money (in this script: 8 variable amounts) but is harder and takes twice as long. Participants make their selection knowingly under 3 different win probabilities (aka they might not win money even if they are successful; particularly not if the win probabilities are low). By default, E selects the Easy task and I selects the Hard task (can be edited under section Editable Parameters).

Procedure

(A) Test:
- 20 minutes total: the number of trials run per participant during that timeframe depends on
- how fast they make their selection
- the type of task they select
- how fast they complete the task
(Treadway et al, 2009, p.4, only use the first 50 trials per participant for their data analyses:
Mean trials completed = 54, SD =4.74, Range = 47–69 trials).

- 3 win probabilities: 88%, 50%, 12% (can be edited under section Editable List; the probabilities are 'true' probabilities and not frequencies)
- hard task reward amounts: $1.24-$4.30 (in this script: in steps of $0.43)
=> 8 levels (1.24,1.68,2.11,2.55,2.99,3.43,3.86,4.3; mean = 2.77)
- each level of probability (3) is paired with each level of hard task reward (8) twice within every 48 trials in this script
=> expected money for successfully completing hard task for (every) 48 trials: $2.77 * 48 * average(0.12, 0.5, 0.88) = $66.48
=> IF twice as many (successful) easy trials are run in the same time frame: = $1 * (2 * 48) * average(0.12, 0.5, 0.88) = $48
=> a maximum payoff can be set in this script (if it's reached, the task is terminated)
- the presentation of the different combinations of hard reward tasks x probabilities was randomized for 2 lists of 48 trials and is presented
in fixed order to each participant (see list.rewards_hard).


Trial Sequence:
Selection Screen (max. 5000ms)*->Ready Screen (1000ms)->Task Screen (max.7s or max.21s)->success/failure feedback screen (2000ms)->potentially win screen (2000ms)

•If no selection is made within 5000ms, the computer randomly selects a task for the participant

(B) Practice:
- 4 trials: The first 2 trials provide the choices (Easy->Hard; if something else is chosen, the choice is "corrected");
for the last 2 trials participants are free to choose either task.
Reward Amounts for the Hard Task (same as for test) are selected randomly from 4 options (without replacement);
Win probabilities (same as for test) are randomly selected (with replacement).
In this script, practice trial provide a reminder description of the tasks for the "Ready" screen (Ready screen is presented for 2000ms)

Instructions

The instructions are not original to Treadway et al (2009). They are provided by Millisecond.
They can be edited under section Editable Instructions.

Summary Data

File Name: effortexpenditureforrewardtask_summary*.iqdat

Data Fields

Raw Data

File Name: effortexpenditureforrewardtask_raw*.iqdat

Data Fields

Parameters

The procedure can be adjusted by setting the following parameters.