Results Experiment 1: Automatic Imitation The three-factorial ANOVA on the cycle time (ms) data yielded a significant main effect of distractor speed, F(1, 18) = 47.07, p,0.001, gp2 = 0.72. As predicted, response cycle times were shorter after seeing a fast, compared to a slow distractor (645 vs. 690 ms; see Figure 3). Trivially, the main effect of habitual speed was also significant, F(1, 18) = 68.57, p,0.001, gp2 = 0.79. There was no significant main effect for the availability of vision, F(1, 18) = 0.01, p.0.05. The only significant interaction was that between distractor speed and habitual speed, F(1, 18) = 12.45, p,0.01, gp2 = 0.41. This reflected the fact that, although the ratio of slow:fast distractor speeds was the same for each habitual speed (150%), the absolute difference between distractor cycle times was greater in habitually slow actions compared to habitually fast actions (see Method, Section 6). The five-factorial ANOVA on the cycle time ratio (%) data yielded a significant main effect of action type compatibility, F(1, 18) = 22.78, p,0.001, gp2 = 0.56, and of plane compatibility, F(1, 18) = 34.56, p,0.001, gp2 = 0.66. In both cases, the cycle time ratio was closer to the display ratio (150%) for compatible than for incompatible trials (109 vs. 106%; 109 vs. 105%, respectively; see Figure 4). Unexpectedly, the main effect of delay was not significant, F(2, 36) = 1.12, p.0.05. Different to the ANOVA on the mean cycle time data (ms), the effect of habitual speed was not significant in the cycle time ratios, confirming that the imitation bias was similarly pronounced at both habitual speeds, when expressed as cycle time ratios. Again, the main effect for the availability of vision was not significant. Automatic Imitation in Rhythmical Actions Figure 4. Automatic imitation experiment: Cycle time ratios (%). Mean cycle time ratios (with standard error of the mean) for the factors delay, action type compatibility, and plane compatibility (SA = Same Action; DA = Different Action; SP = Same Plane; DP = Differ- ent Plane). The cycle time ratio in the distractor actions was 150%. doi:10.1371/journal.pone.0046728.g004 Only two significant interactions were found. First, the interaction between action type and plane compatibility was significant, F(1, 18) = 16.23, p,0.01, gp2 = 0.47. Pairwise compar- isons using Bonferroni corrections showed that responses in the fully compatible SA/SP condition were biased significantly more by the different distractor speeds than responses under each of the Figure 3. Automatic imitation experiment: Cycle times (ms). Mean cycle times for the factors habitual speed, distractor speed, and the availability of vision of the hand. The error bars show the standard error of the mean. doi:10.1371/journal.pone.0046728.g003 PLOS ONE | www.plosone.org 6 October 2012 | Volume 7 | Issue 10 | e46728