Effects of feature integration in a hands-crossed version of the Social Simon paradigm

In order to better compare our findings with those of the Welsh (2009) study, we ran an additional analysis on the present experimental data with crossed hands including the dataset of a previous study in which another group of participants performed exactly the same task with hands uncrossed (Liepelt et al., 2011). This analysis included the factors Compatibility (Compatible vs. Incompatible), Preceding Compatibility on trial (N−1), and Group (Crossed vs. Uncrossed). The analysis was performed separately for the Individual go/nogo task and the Joint go/nogo task. For the Individual go/nogo task this analysis showed no overall SSE effect, but a sequential modulation across both groups (Crossed, Uncrossed), F(1, 46) = 50.96, MSe = 132.71, p < 0.001, partial η² = 0.53. The sequential modulation did not differ between crossed- and uncrossed-effector conditions for the Individual go/nogo tasks, F(1, 46) < 1, partial η² = 0.01. For the Joint go/nogo tasks, however, we found a significant overall SSE across both groups (Crossed, Uncrossed), F(1, 46) = 7.26, MSe = 156.07, p < 0.05, partial η² = 0.14, which was, however, entirely driven by the 9 ms Simon effect in the uncrossed-effector condition (compared to the 0 ms in the hands-crossed condition). This enlargement of the SSE in the uncrossed-effector condition compared to the crossed-effector condition was also reliable, F(1, 46) = 5.27, MSe = 156.07, p < 0.05, partial η² = 0.10. Further, we found a sequential modulation across both groups (Crossed, Uncrossed) for the Joint go/nogo tasks, F(1, 46) = 174.44, MSe = 100.66, p < 0.001, partial η² = 0.79, which did not differ between crossed- and uncrossed-effector conditions, F(1, 46) < 1, partial η² = 0.002.