(1994) was that normal, healthy decision makers would learn over time to choose cards from the two advantageous decks only, assuming that they would focus on the long-term outcome and not be misled by the high immediate rewards. The initial assumption made by Bechara et al. The expected values of the decks differ so that two decks are associated with high immediate rewards but long-term overall loss (disadvantageous decks A and B), and two decks yield lower immediate rewards but long-term overall gains (advantageous decks C and D). This task requires participants to repeatedly draw cards from four possible card decks. It has become most popular for studying differences between clinical groups (e.g., Grant et al., 2000 Bechara et al., 2001 Cavedini et al., 2004 Bark et al., 2005 Bolla et al., 2005 Shurman et al., 2005 Toplak et al., 2005 Boeka and Lokken, 2006 Garon et al., 2006 Tchanturia et al., 2007 Hermann et al., 2009 Liao et al., 2009 Brogan et al., 2010, 2011 Davis et al., 2010 Fridberg et al., 2010). The Iowa Gambling Task (IGT, Bechara et al., 1994) has been widely used to assess decision-making under uncertainty. In addition, differences between clinical groups can be assessed for each factor individually. In sum, our model facilitates a more focused conclusion about the factors guiding decision-making in the IGT. Consequently, long-term outcome alone is not able to drive choice behavior on the IGT. However, subjects in general do not learn to solely base their preference for particular decks on expected long-term outcome. Further, cluster analysis of estimated feature weights revealed sub-groups of participants with distinct weight patterns and associated advantageous decision behavior. This is reflected in the relationship between the weights for gain frequency (highest), loss frequency (intermediate), and long-term outcome (lowest). However, among options with low-frequency gains, subjects learned to distinguish between choices that led to advantageous and disadvantageous long-term consequences. Subjects preferred choices associated with high-frequency gains to those with low-frequency gains, regardless of long-term outcome. Results from 119 healthy young subjects suggest that choice behavior is predominantly influenced by gain and loss frequency. With our proposed model it is possible to disentangle and quantify the impact of each of these features. Offering an alternative way of modeling IGT data, we propose to use a system of linear equations to estimate weights that quantify the influence of each individual feature on decision-making in the IGT. Since choice options are characterized by gain and net loss frequency in addition to long-term outcome, we hypothesized that a combination of features rather than a single feature would influence participants’ choices. Recently, several studies have shown that healthy subjects do not meet the basic predictions of the task (i.e., prefer options with positive long-term outcome), hence questioning its basic assumptions. The Iowa Gambling Task (IGT) has been widely used to assess differences in decision-making under uncertainty. 4 Mind and Brain Institute, Berlin School of Mind and Brain, Humboldt University Berlin, Berlin, Germany.
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