Exp Brain Res (2011) 211:531–545 539 Fig. 4 Reaction times for 3rd PP trials in both attention conditions in experiments 1 and 2. Left Experiment 1. Middle Cooperation group. Right Competition group. The single-attention condition is depicted in grey (squares), the joint-attention condition in black (triangles) were still ﬂat [ts (45) \ 1] (see Fig. 4 for 3rd PP trials in experiments 1 and 2). There was a signiﬁcant two-way interaction of attention and perspective of ﬁrst hand in RTs [F(1, 45) = 4.1, p \ .05]. This was due to the fact that attention affected only 1st PP trials, but not 3rd PP trials [t(45) = 1.2, p = .23]. Participants were faster in joint-attention trials as compared to individual attention trials in the competition group [t(21) = 2.5, p \ .05], but not in the cooperation group [t(23) \ 1]. Cooperation only Reaction times Increasing angles of rotation elicited an increase in RTs [t(23) = 8.4, p \ .001]. We found a signiﬁcant difference between slopes in the single and the joint-attention condi- tion; slopes were considerably ﬂatter when the other partic- ipant was attending as well [t(23) = 2.5, p \ .05]. Intercepts were not affected by attention [t(23) = 1.5, p = .14]. Errors Mean error rates were 7.1%. Error rates increased with increasing angle of rotation [t(23) = 3.5, p \ .01]. No effect of attention on slopes was present in error rates [t(23) \ 1]. There were no effects on intercepts [t(23) \ 1]. Competition only Reaction times Increasing angles of rotation elicited an increase in RTs [t(21) = 5.7, p \ .001]. We found a signiﬁcant difference between slopes in the single and the joint-attention condi- tion; slopes were signiﬁcantly ﬂatter when the other par- ticipant was attending as well [t(21) = 2.2, p \ .05]. Analysis of intercepts revealed no signiﬁcant differences [t(21) = 1, p = .33]. Errors Mean error rate was 8,6%. Error rates increased with increasing angle of rotation [t(21) = 4,9, p \ .001]. No effect of attention on slopes was present in error rates [t(21) = 1.5, p [ .1]. Intercepts were not inﬂuenced by attention [t(21) \ 1]. Discussion The results replicate the main ﬁnding of experiment 1. When both participants attended jointly, slopes reﬂecting the relation between RTs and angle of rotation were ﬂatter than when participants attended alone. The more stimuli were rotated towards the co-attending person, the more participants beneﬁtted from the other’s attention. The joint- 123