Performance was measured by: 1) response time (RT); 2) performance decrement (PD) defined as the difference in correct response rates in 0-back and 2-back conditions (Jansma et al., 2000). The 2-back load was utilized as it maintained cognitive demand without exceeding capacity constraints (Callicott et al., 1999, Sweet et al., 2008) with satisfactory accuracy (77.9%±16.7 here). RTs less than 100 milliseconds were considered anticipatory responding and removed from subsequent analyses. All performance measures were normally distributed (KS test, p’s>0.07) in SPSS version 17 (Chicago, IL).
