Money Food Delay Discounting Task

Background

Classic Delay Discounting (DD) procedures are research tools to help investigate the degree to which the subjective value of a monetary reward decreases as a function of wait time. However, instead of focusing on monetary rewards, other reward commodities such as 'food' can also be studied in discounting paradigms, with 'food' being of particular interest in obesity research.

One of the first studies to focus on food discounting was conducted by Walter Mischel and colleagues in 1972 with children. Their basic test - later coined the 'Marshmallow Test' for delay gratification - was to study children's behavior when confronted with the choice to eat a single marshmallow that sits right in front of them or to wait some time to get rewarded with more marshmallows.

The Delay Discounting Task with Money and Food -published by Amy Odum and colleagues in 2006- is a computerized assessment tool of discounting of both monetary and food rewards. The basic choice task for either commodity is the hypothetical choice between a small reward right now versus a larger reward after a delay. Both commodities are tested in a within-subjects design.

Odum et al assess 2 indifference points for each of 7 temporal delays per reward commodity: (a) one in which the immediate value gets systematically decreased (e.g. from $10 down to $0.10) regardless of choice and (b) another in which the immediate value gets systematically increased (e.g. from $0.10 to $10). The indifference points are found when participants switch response patterns 'consistently' and the final indifference point for each delay is then calculated as the arithmetic mean of the increasing and decreasing indifference points.

Comparing discount rates for these two commodities, Odum et al found that the difference in observed discounting rates for food and money is fairly robust across different amounts, with food discounting consistently occurring at a steeper rate.

Task Procedure

After learning about the basic choice task in the Delay Discounting Task with Money and Food , a participant selects a preferred food dish from two provided picture options (e.g. 'maccaroni and cheese' vs. 'chicken nuggets') which is then the food reward used throughout the task. Each of the 7 delays is tested in a separate round with fixed orders of food and money blocks. For example, for a particular delay a participant might work first on decreasing MONEY trials (26 trials), followed directly by the increasing MONEY trials (26 trials) before working on the decreasing/increasing FOOD trials (also 26 trials each).

During each trial (e.g. a 'Food' trial) a participant sees the picture of the selected food and gets the choice between an immediate smaller reward (e.g. '5 servings of chicken nuggests NOW') vs. a delayed larger reward (e.g. '10 servings of chicken nuggets in 1 hour'). The participant selects the preferred option via mouse click/touch. If the participant works on the increasing Food condition, the next trial would increase the promised servings of the immediate food servings regardless of the participant's choice (e.g. from 5 servings to 5.1 servings). The same principle applies to the decreasing condition.

What it Measures

The Delay Discounting Task with Money and Food Task is a behavioral assessment tool for choice impulsivity and delay gratification

Psychological domains

• Inhibitory Control: The ability to withhold a "rash" response for immediate gain in favor of a more valuable future outcome.

Main Performance Metrics

• Indifference Points: Estimated indifference points for various delays

Psychiatric Conditions

Higher discount rates k are linked to the following conditions:

• Addictive Disorders
• Substance Abuse
• Gambling
• Attention Deficit Hyperactivity Disorder (ADHD)
• Bipolar Disorder
• Borderline Personality Disorder (BPD)