538 Fig. 3 Reaction times and linear ﬁts for 1st PP trials in both attention conditions of experiment 2. Left Cooperation group. Right Competition group. The single-attention condition is depicted in grey (squares), the joint-attention condition in black (triangles). The linear trend line for the single condition is depicted in grey, R2 = .99 in the cooperation group and R2 = .98 in the competition group. The linear trend line for the joint condition is shown in black, R2 = .95 in the cooperation group and R2 = .97 in the competition group Additional analyses were performed on the 1st PP data with- out the 180 rotation condition and separately on 3rd PP trials. Results Two participants in the cooperation condition and four participants in the competition condition were excluded due to error rates that were more than two SDs above average. Reaction times RTs increased signiﬁcantly with increasing rotation [t(45) = 9.4, p \ .001, see Fig. 3]. There was a signiﬁcant difference between slopes in the single and the joint- attention condition. Overall, slopes were ﬂatter when the other participant was attending as well [F(1, 45) = 11.2, p \ .01, see Table 1]. There was no main effect of type of social interaction [F(1, 45) \ 1] and no signiﬁcant two- way interaction of attention and social interaction [F(1, 45) \ 1]. Intercepts were signiﬁcantly smaller in the competition condition than in the cooperation condition [F(1, 45) = 4.5, p \ .05]. Intercepts were marginally higher in the joint-attention condition compared to the single-attention condition [F(1, 45) = 3.4, p = .07]. There was no signiﬁcant two-way interaction of attention and social interaction [F(1, 45) \ 1]. Exclusion of 180 data All ﬁndings held when data at the 180 level were excluded from the analysis. RT increased signiﬁcantly with increasing 123 Exp Brain Res (2011) 211:531–545 angle of rotation [t(45) = 8.8, p \ .001], and slopes were signiﬁcantly ﬂatter in the joint-attention condition [t(45) = 2.1, p \ .05]. There was no main effect of type of social interaction [F(1, 45) \ 1] and no signiﬁcant two-way interaction of attention and social interaction [F(1, 45) \ 1]. Intercepts were signiﬁcantly smaller in the competition condition than in the cooperation condition [F(1, 45) = 3.5, p \ .05]. Intercepts did not differ between attention condi- tions [F(1, 45) \ 1]. There was no signiﬁcant two-way interaction of attention and social interaction [F(1, 45) \ 1]. Errors Errors rates increased signiﬁcantly with increasing level of rotation [t(45) = 3.7, p \ .01]. No effect of attention or social interaction on slopes was present in error rates [Fs(1, 45) \ 1]. Intercepts were not affected by any of the factors [Fs(1, 45) \ 1]. Slopes and intercepts are listed in Table 1. Additional analysis including 3rd PP trials A 2 9 2 9 2 ANOVA with the factors perspective of ﬁrst- hand picture, attention and social interaction showed a signiﬁcant main effect of the factor perspective of ﬁrst- hand picture [RTs: F(1, 45) = 9.7, p \ .01; errors: F(1, 21) = 7.3, p \ .01] on slopes. This was due to the fact that the rotation curve was nearly ﬂat on trials in which the ﬁrst- hand picture was shown from a third-person perspective [RTs and errors: ts(45) \ 1]. RTs were marginally faster on 0 trials than on trials including rotations (contrast between 0 and all later degrees: [F (1, 45) = 2.9, p = .09]. When 0 was excluded from the analysis, slopes