Iowa Gambling Task (IGT)

Original Scheme

This implementation is adapted from the Bechara et al. (1994) schedules. The procedure in this version:

• There were 4 decks of cards (A, B, C, and D)
• Participants had to choose in total 100 cards, one at the time
• Each time they choose a card, they get feedback about winning and/or losing some money
• Participants did not know what each card would yield in advance (i.e., like a lottery)
• Participants started with a "loan" of $2000 and were told to make a profit
• Decks A and B always yielded $100
• Decks C and D always yielded $50
• Every card carries a fixed reward and triggers a fixed penalty with a fixed probability. Decks A and B are disadvantageous: deck A pays $100 but carries a 50% chance of a $250 penalty, and deck B pays $100 but carries a 10% chance of a $1250 penalty. Decks C and D are advantageous: deck C pays $50 with a 50% chance of a $50 penalty, and deck D pays $50 with a 10% chance of a $250 penalty. These schedules are adapted from the Bechara et al. (1994) schedules, and their long-run expected values match the original task (average net loss of $250 per 10 draws from A/B, average net gain of $250 per 10 draws from C/D).

Analysis

When you are analyzing the data, you need to think carefully about what exactly you want to find out.

One interesting outcome is how often people decided for the "high risk" decks (A/B) or the "low risk" decks (C/D).

Another interesting question is how long it took people to decide before they made a low or high risk decision.

"Decks A and B are disadvantageous in the long run because they cost the most in the long run, while decks C and D are advantageous because they result in an overall gain in the long run." (Bechara et al., 1994, p.10).

Neuroscience Background

The task was originally developed to detect problems patients with damage to the ventromedial prefrontal cortex. This part of the brain is, among other things, involved in processing risk, fear, emotion, and decision making:

Following damage to the ventromedial prefrontal cortex, humans develop a defect in real-life decision-making, which contrasts with otherwise normal intellectual functions. Currently, there is no neuropsychological probe to detect in the laboratory, and the cognitive and neural mechanisms responsible for this defect have resisted explanation. Here, using a novel task which simulates real-life decision-making in the way it factors uncertainty of premises and outcomes, as well as reward and punishment, we find that prefrontal patients, unlike controls, are oblivious to the future consequences of their actions, and seem to be guided by immediate prospects only. This finding offers, for the first time, the possibility of detecting these patients' elusive impairment in the laboratory, measuring it, and investigating its possible causes.

— Bechara et al. 1994