A total of 16 studies (Egan et al. 2001; Bilder et al. 2002; Joober et al. 2002; Malhotra et al. 2002; Mattay et al. 2003; Tsai et al. 2003; Rosa et al. 2004; Taerk et al. 2004; Bruder et al. 2005; Galderisi et al. 2005; Ho et al. 2005; Lipsky et al. 2005; Minzenberg et al. 2006; Ohnishi et al. 2006; Rybakowski et al. 2006; Szoke et al. 2006) published between 2001 and 2006 and comprising 26 independent samples were identified by the search strategy and met the inclusion criteria (Table 4). Where data were not available in an appropriate format for inclusion, we attempted to contact authors directly. Data from two studies (Egan et al. 2001; Taerk et al. 2004) comprised normalized t scores (i.e. higher scores reflecting better performance) and were reversed for consistency with other studies. One study (Ohnishi et al. 2006), comprising two independent samples, had to be excluded because we could not obtain appropriate data.
