We tested two cognitive variables – neurocognition and social cognition (Table 1). The neurocognition variables were the composite scores computed from predefined domains-working memory, verbal memory, processing speed, reasoning and vigilance. Details on the composite score, domain scores, neurocognitive tests used to compute domain scores, and measurement characteristics are provided in Keefe et al. (2006). Social cognition was measured by the facial emotion recognition task (Kerr and Neale, 1993). Since the task measures facial emotion recognition, is only one component of social cognition from here on we refer to it as emotion recognition. Briefly, in this task subjects are asked to discriminate if two faces presented have the same emotional expression. The total score is the number of correctly discriminated faces and ranges between 0 and 30. The data distribution for this variable was skewed with 16 subjects scoring <15. Subsequently, we rescaled the variable to a lowest score of 15 and all subjects who scored 15 or below were assigned a value of 15.
