Are Normal Decision-Makers Sensitive to Changes in Value Contrast under Uncertainty? Evidence from the Iowa Gambling Task

Lin C-H (2014) Are Normal Decision-Makers Sensitive to Changes in Value Contrast under Uncertainty? Evidence from the Iowa Gambling Task. PLoS ONE 9(7): e101878. doi:10.1371/journal.pone.0101878 Are Normal Decision-Makers Sensitive to Changes in Value Contrast under Uncertainty? Evidence from the Iowa Gambling Task We-Kang Lee 0 Yi-An Su 0 Tzu-Jiun Song 0 Yao-Chu Chiu 0 Ching-Hung Lin 0 Cosimo Urgesi, University of Udine, Italy 0 1 Department of Psychology, Soochow University , Taipei, Taiwan , 2 Department of Psychology, National Chengchi University , Taipei, Taiwan , 3 Biomedical Engineering R&D Center, China Medical University Hospital , Taichung, Taiwan , 4 Biomedical Electronics Translational Research Center, National Chiao Tung University , Hsinchu, Taiwan , 5 Department of Psychology, Kaohsiung Medical University , Kaohsiung , Taiwan The Iowa Gambling Task (IGT) developed by Bechara et al. in 1994 is used to diagnose patients with Ventromedial Medial Prefrontal Cortex (VMPFC) lesions, and it has become a landmark in research on decision making. According to Bechara et al., the manipulation of progressive increments of monetary value can normalize the performance of patients with VMPFC lesions; thus, they developed a computerized version of the IGT. However, the empirical results showed that patients' performances did not improve as a result of this manipulation, which suggested that patients with VMPFC lesions performed myopically for future consequences. Using the original version of the IGT, some IGT studies have demonstrated that increments of monetary value significantly influence the performance of normal subjects in the IGT. However, other research has resulted in inconsistent findings. In this study, we used the computerized IGT (1X-IGT) and manipulated the value contrast of progressive increments (i.e., by designing the 10X-IGT, which contained 10 times of progressive increment) to investigate the influence of value contrast on the performance of normal subjects. The resulting empirical observations indicated that the value contrast (1X- vs. 10X-IGT) of the progressive increment had no effect on the performance of normal subjects. This study also provides a discussion of the issue of value in IGT-related studies. Moreover, we found the ''prominent deck B phenomenon'' in both versions of the IGT, which indicated that the normal subjects were guided mostly by the gain-loss frequency, rather than by the monetary value contrast. In sum, the behavioral performance of normal subjects demonstrated a low correlation with changes in monetary value, even in the 10X-IGT. - Funding: The authors would like to thank the National Science Council of Taiwan for financially supporting this study under Contract No. NSC 99-2410-H-031025. The fifth author was also supported in part by the Aim for the Top University Plan of National Chiao Tung University and the Ministry of Education, Taiwan (MOE-100W960) and by Kaohsiung Medical University (KMU-Q103022). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. The Iowa Gambling Task (IGT) was developed by Bechara et al. [1] to examine the differences in decision making between patients with ventromedial prefrontal cortex (VMPFC) lesions and normal subjects and to prove the somatic marker hypothesis (SMH), according to which people may be guided by their emotions to make fast and rational decisions under complex and uncertain situations [2]. IGT serial studies [1,3,4,5,6] specifically indicated that because of the effects of brain lesions on emotional processing, patients with VMPFC lesions are unable to form somatic markers (indexed by skin conductance response (SCR)) that can guide people in making rational decisions, and consequently, perform myopically in decision-making tasks [3,4,5,6]. In the original IGT, participants were presented with four decks of cards (i.e., decks A, B, C, and D) and required to choose cards manually. The gain-loss structure of the ten selections in each deck is designed as a section and is repeated four times. The expected value in each section of the original IGT is steady and unchanged. For each selection, participants are informed of the outcome of wins and losses. Although each selection in disadvantageous decks A and B carries an immediate reward of $100, some trials also contain an uncertain punishment (losses of $150 to $1250). Over the long run, selecting from decks A and B causes negative outcomes. In contrast, every selection in advantageous decks C and D carries an immediate reward of $50, but in some trials also contains an uncertain punishment (losses of $50 to $250). Over the long run, selections from decks C and D cause positive outcomes. Furthermore, decks A and C contain 5 losses in every section, but decks B and D have only 1 loss (see Table 1). According to the prediction of the SMH, normal participants will avoid the bad decks and select more from the good decks due to the formation of somatic markers. The results reported by Bechara et al. [1,4] proved the SMH; however, the performance of patients with VMPFC lesions showed a reversed outcome (i.e., they preferred decks A and B over decks C and D). The IGT researchers demonstrated that the decision-making deficit in patients with VMPFC lesions may be due to insensitivity to future consequences (see details in [5]). Furthermore, in their Deck A (Bad) Deck C (Good) Deck D (Good) Deck B (Dad) 10 gains 1 loss Gain in each selection Modified from Bechara et al. [1] doi:10.1371/journal.pone.0101878.t001 10 gains 5 losses 10 gains 1 loss 10 gains 5 losses attempt to normalize the performance of patients with VMPFC lesions by enhancing the patients sensitivity to future consequences, Bechara et al. increased the prospective rewards and penalties gradually in each section of the original IGT and developed a computerized version of the IGT, thereby increasing the expected value in each section of the computerized IGT dynamically. The gains in decks A and B and decks C and D were programmed at an average of $100 or $50, respectively, in the first section of 10 cards and progressively increased by $10 or $5 in consecutive sections in decks A and B and decks C and D, respectively. Additionally, in each section of decks A and C, an additional loss trial was added, but the value remains the same (with losses ranging from $150 to $350 in deck A and $25 to $75 in deck C, which is identical to the original IGT). Therefore, 5 losses are contained in the first section, 6 in the second section, and so on. In each section of decks B and D, the value increases, but the frequency remains the same. The net difference (the expected value of a section) of decks A and B increases by $150 in a negative direction, whereas decks C and D increase by $25 in a positive direction from the second to (...truncated)