Millisecond - aka Cambridge Gambling Task

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

Created: January 06, 2014

Last Modified: January 09, 2025 by K. Borchert (katjab@millisecond.com), Millisecond

Script Copyright © Millisecond Software, LLC

Background

This script implements the Millisecond Gambling Task (MGT), a decision-making and risk-taking behavioral task similar to the Cambridge Gambling Task (CGT).

References

Rogers, R.D., Everitt, B.J., Baldacchino, A., Blackshaw, A.J, Swainson, R., Wynne, K., Baker, N.B., Hunter, J., Carthy, T., Booker, E., M. London, M., Deakin, J.F.W., Sahakian, B.J., & Robbins, T.W. (1999). Dissociable Deficits in the Decision-Making Cognition of Chronic Amphetamine Abusers, Opiate Abusers, Patients with Focal Damage to Prefrontal Cortex, and Tryptophan-Depleted Normal Volunteers: Evidence for Monoaminergic Mechanisms. NEUROPSYCHOPHARMACOLOGY, 20, 322–339.

Duration

20 minutes

Description

Participants are given 10 boxes. Some of these boxes are red, the others are blue. They are told that a yellow token is hidden under one of these boxes and they have to guess the color of the box under which the yellow token is hidden. Once they decide on the color, they are asked to bet points on this choice: the computer provides the bets in either ascending (bets get bigger) or descending order (bets get smaller) and participants are asked to click on a bet when they want to bet this number of points. If they win, the bet number is added to their total points. If they lose the bet number is taken away from their total points.

Procedure

4 ratios of blue/red (as well as red/blue) boxes are tested within participants: 1/9, 2/8, 3/7, 4/6

(a) Practice Block: selection of box color (the color of the box that hides token) only
• 5 trials with a fixed order of blue/red ratios (see LISTS -> list.rednumbers_practice) and fixed order
of token position (see LISTS -> list.tokenbox_practice)

counterbalanced order (by groupnumber) of (b) and (c)
=> odd groupnumbers run Ascending -> Descending
=> even groupnumbers run Descending -> Ascending

(b) Ascending Bet Block: after selection of box color, bets are offered to participants
• by default: 4 blocks with 9 trial sequences aka "displays" each (see Rogers et al, 1999);
participants start with 100 points at the beginning of each block (values.totalpoints- editable value)
( according to Rogers et al, 1999, the trial sequence for one block is prematurely aborted if the
total points go below 2, the total points reset to 100 and the next block is started)

• displays (ratios) are presented in fixed order: order was pseudo-randomly determined by Millisecond.
In this script all 4 ratios are sampled 9 times across all 36 trials; half the time there are more red, half
the time there are more blue boxes -> to change the fixed order go to LISTS -> list.rednumbers_ascending

• fixed order of token position: the order of the token position (box1-10) was pseudo-randomly determined by Millisecond.
In 1/6 of all trials the better choice (based on probability) leads to a loss (see LISTS -> list.tokenbox_ascending)

• 5 bets are provided in fixed order of proportions of current total points (see LISTS -> list.betpercentages_asc).

• bets are starting small and get bigger (each bet is presented for parameters.betduration, default 5s);
sounds accompany each bet (the higher the sound, the higher the bet)

• if no bet is selected the last bet is selected by default

(b) Descending Bet Block:
• bets are starting big and get smaller
• different fixed orders for ratios/token position
=> no other differences to Ascending Bet Blocks

Instructions

Instructions are not original to the task. They are provided by Millisecond
as htm/html pages and can be edited by changing the provided htm/html files.
To edit htm/html-files: open the respective documents in simple Text Editors such as TextEdit (Mac)
or Notepad (Windows).

Scoring

Risk Adjustment:

Delay Aversion:

Summary Data

File Name: millisecondgamblingtask_summary*.iqdat

Data Fields

Raw Data

File Name: millisecondgamblingtask_raw*.iqdat

Data Fields

Parameters

The procedure can be adjusted by setting the following parameters.