Reaction, F (17.07, 54.87) = 26.78, p < 0.001 (Greenhouse?Geisser corrected, = 0.27). This effect was described by a highly significant linear trend, F (1, 20) = 53.14, p < 0.001, indicating a continuous decrease of relatedness ratings with increasing latency of gaze reactions.COMBINED ANALYSIS OF GAZE-FOLLOWING IN EXPERIMENTS 1A AND 1BRESULTSEXPERIMENT 1AThe ratings of relatedness of PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19913039 the avatar’s gaze reactions are depicted in Figure 2A. A two-way ANOVA for PF-562271 repeated-measures with the factors gaze reaction (joint vs. non-joint) and latency (0?000 ms in steps of 400 ms) showed a main effect of gaze reaction: as expected, gaze-following reactions resulting in JAIn a separate set of analyses, we focused only on JA and compared the JA trials from Experiment 1a to Experiment 1b. The crucial difference between these two experiments was that in Experiment 1a the putative interaction partner had an additional option to react and could also 
avert his/her gaze, whereas inFIGURE 
2 | (A) The results from Experiment 1a, in which the interaction partner could either follow the gaze of the participant to engage in joint attention (JA) or avert his/her gaze to the other object to engage in non-joint attention (NJA). (B) In Experiment 1b the interaction partner always engagedin JA, only the latency of the gaze reaction is varied. For better comparability, the joint attention data of Experiment 1a (JA in the context of NJA as another option to act) are plotted together with the data from Experiment 1b (JA only).www.frontiersin.orgDecember 2012 | Volume 3 | Article 537 |A-83-01 Pfeiffer et al.Dynamics of social gazeExperiment 1b the virtual character would always follow participants’ gaze, which participants were informed of during the instruction. In order to assess the influence of a second option to react on the perception of latency of gaze-following, we conducted a two-way repeated-measures ANOVA including only the JA trials from Experiment 1a and all trials from Experiment 1b with experiment as a between-subjects factor. There was a significant interaction between the factors experiment and relatedness rating, F (4.27, 196.3) = 11.02, p < 0.001 (Greenhouse?Geisser corrected, = 0.43). As Figure 2B shows, ratings from Experiment 1b (open circles), which consisted only of JA trials, suggest that participants experience gaze-following reactions as most related to their own gaze shift when they follow with a latency of 400 ms (M = 3.26, SD = 0.68). In Experiment 1a (filled circles) ratings for gaze reactions with a latency of 400 ms were significantly lower (M = 2.86, SD = 0.61), as shown by a t -test for independent samples, t (46) = -2.16, p = 0.038. Here, visual inspection of data suggests that maximum relatedness ratings were not reached before 800 ms. Furthermore, in Experiment 1b there was a continuous linear decrease of relatedness ratings beginning at 400 ms. This was confirmed by a highly significant linear trend, F (16.06, 42.67) = 53.14, p < 0.001, which is absent in the data of Experiment 1a, F (0.47, 17.49) = 0.7, p = 0.41. Taken together, these results suggest that when the interaction partner has no other choice but following participants' gaze, relatedness ratings peak earlier as compared to a context in which the other can either react by gaze-following or by gaze aversion. In addition, participants' are less sensitive to the latency of gaze-following in the context of action alternatives.EXPERIMENTSD = 0.35). Furthermore, standard deviations.Reaction, F (17.07, 54.87) = 26.78, p < 0.001 (Greenhouse?Geisser corrected, = 0.27). This effect was described by a highly significant linear trend, F (1, 20) = 53.14, p < 0.001, indicating a continuous decrease of relatedness ratings with increasing latency of gaze reactions.COMBINED ANALYSIS OF GAZE-FOLLOWING IN EXPERIMENTS 1A AND 1BRESULTSEXPERIMENT 1AThe ratings of relatedness of PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19913039 the avatar’s gaze reactions are depicted in Figure 2A. A two-way ANOVA for repeated-measures with the factors gaze reaction (joint vs. non-joint) and latency (0?000 ms in steps of 400 ms) showed a main effect of gaze reaction: as expected, gaze-following reactions resulting in JAIn a separate set of analyses, we focused only on JA and compared the JA trials from Experiment 1a to Experiment 1b. The crucial difference between these two experiments was that in Experiment 1a the putative interaction partner had an additional option to react and could also avert his/her gaze, whereas inFIGURE 2 | (A) The results from Experiment 1a, in which the interaction partner could either follow the gaze of the participant to engage in joint attention (JA) or avert his/her gaze to the other object to engage in non-joint attention (NJA). (B) In Experiment 1b the interaction partner always engagedin JA, only the latency of the gaze reaction is varied. For better comparability, the joint attention data of Experiment 1a (JA in the context of NJA as another option to act) are plotted together with the data from Experiment 1b (JA only).www.frontiersin.orgDecember 2012 | Volume 3 | Article 537 |Pfeiffer et al.Dynamics of social gazeExperiment 1b the virtual character would always follow participants’ gaze, which participants were informed of during the instruction. In order to assess the influence of a second option to react on the perception of latency of gaze-following, we conducted a two-way repeated-measures ANOVA including only the JA trials from Experiment 1a and all trials from Experiment 1b with experiment as a between-subjects factor. There was a significant interaction between the factors experiment and relatedness rating, F (4.27, 196.3) = 11.02, p < 0.001 (Greenhouse?Geisser corrected, = 0.43). As Figure 2B shows, ratings from Experiment 1b (open circles), which consisted only of JA trials, suggest that participants experience gaze-following reactions as most related to their own gaze shift when they follow with a latency of 400 ms (M = 3.26, SD = 0.68). In Experiment 1a (filled circles) ratings for gaze reactions with a latency of 400 ms were significantly lower (M = 2.86, SD = 0.61), as shown by a t -test for independent samples, t (46) = -2.16, p = 0.038. Here, visual inspection of data suggests that maximum relatedness ratings were not reached before 800 ms. Furthermore, in Experiment 1b there was a continuous linear decrease of relatedness ratings beginning at 400 ms. This was confirmed by a highly significant linear trend, F (16.06, 42.67) = 53.14, p < 0.001, which is absent in the data of Experiment 1a, F (0.47, 17.49) = 0.7, p = 0.41. Taken together, these results suggest that when the interaction partner has no other choice but following participants' gaze, relatedness ratings peak earlier as compared to a context in which the other can either react by gaze-following or by gaze aversion. In addition, participants' are less sensitive to the latency of gaze-following in the context of action alternatives.EXPERIMENTSD = 0.35). Furthermore, standard deviations.