Results from the present study largely support the capability model of individual differences in EEG asymmetry, which asserts that state emotion manipulations will be a more powerful indicator of individual differences (in this case, individual differences associated with depression status) than resting sessions, since emotion response systems (approach and withdrawal motivational tendencies, for example) are more likely to be activated. Depressed individuals showed relatively less left frontal activity than never-depressed individuals during approach- and withdrawal-related facial expressions, consistent with previous research on state emotion paradigms in dysphoric samples (e.g., Harmon-Jones et al., 2002; Nitschke et al., 2004; Shankman et al., 2007; Stewart et al., 2011). EEG asymmetry scores based on CSD-transformed data, however, were more consistent across task and resting data. Consistent with other findings (Velo et al., 2012, Stewart, Bismark et al., 2010), the CSD transform may be advantageous for examining stable trait estimates of frontal EEG asymmetry.
