The effect of reward magnitude differences on choosing disadvantageous decks in the Iowa Gambling Task.

In the Iowa Gambling Task, participants have to develop a long-term profitable monetary scenario in a situation of uncertainty and a conflict between the chance of encountering an immediate large reward (100 US dollars) in two long-term loosing decks (A and B; -250 US dollars per 10 cards) and the chance of encountering an immediate small reward (50 US dollars) in two long-term winning decks (C and D; +250 US dollars per 10 cards). The ratio of the immediate rewards in decks A/B and C/D is thus 2:1. Here, we manipulated these differences in reward magnitude between the advantageous (C/D) and disadvantageous (A/B) decks, while keeping the net gains and losses per 10 cards the same, to assess the impact of the conflict between immediate and distant pay-off on choice behaviour. Participants selected less cards from disadvantageous decks and won more money when the reward magnitude difference was decreased, A/B:C/D=1:1, while they selected more cards from disadvantageous decks and lost more money when reward magnitude differences were increased, A/B:C/D=4:1 and 6:1. This study shows that the outcome in the Iowa Gambling Task is sensitive to differences between the magnitude of immediate rewards in the advantageous and disadvantageous decks.