The Iowa gambling task (Bechara et al., Cognition 50:7-15, 1994) is designed to simulate a decision making problem under ambiguity, in which the degree of reliance on emotional cues arising from previous experiences contributes to perform advantageously. Recent studies based on the appraisal tendency framework demonstrated that emotional certainty (associated with intuitive strategies) leads to a more advantageous decision pattern, whereas emotional uncertainty (associated with deliberative strategies) impairs the performance in the IGT (Bagneux et al., Motivation and Emotion 37(4):818-827, 2013; Bollon and Bagneux, Cognition and Emotion 27(2):376-384, 2013). Due to the problems in the IGT (Dunn et al., Neuroscience and Biobehavioral Reviews 30:239-271, 2006; Steingroever et al., Psychological Assessment 25(1):180-193, 2013), however, it is an open question to what extent the disadvantageous IGT performance in the uncertainty conditions was based on risky decision making. Addressing the main criticisms on the IGT, the primary aim of the present study is to provide a further explanation for the underlying source of the IGT impairment led by uncertainty appraisals. In line with previous research, we found that participants in the certainty-associated emotion condition (disgust) outperformed those in uncertainty-associated conditions (fear, sadness) in the gambling game. Detailed four-deck format analyses on decision patterns and knowledge levels provided supporting evidence for our main hypothesis that the weak IGT scores in the uncertainty conditions can be summarized as a failure to anticipate the badness and the goodness of the most difficult decks, and a dominant preference for a risky option with high immediate gains and infrequent losses.