604 Procedure Priming task A modiﬁed version of the Scrambled Sentence Priming task used in Leighton et al. (2010) was employed. There were 36 trials in total. Each trial showed ﬁve words arranged vertically down the centre of the screen. The task was to pick 4 of the 5 words to make a grammatically correct sentence. Words were presented in Arial, font size 24. The colour of the words (red, green, black or blue) varied randomly over trials in order to suggest to the par- ticipant that the aim of the task was to investigate the effect of colour on word processing and hence distract from the priming nature of the task. Two versions of the priming task were used: one to prime a pro-social attitude, one to prime a non-social attitude. For both versions, 24 of the 36 trials contained a priming word, that is, they contained an adjective or verb semantically related to the target attitude (pro-social or non-social). Twelve of the sentences were neutral (e.g. ‘‘the car was small’’). This corresponds to a 2/3 saturation level, which has previously been shown to be effective for priming target attitudes without provoking conscious awareness of this target attitude (R. Van Baaren, personal communication). For the pro-social priming version, the 24 priming words were: friend, talkative, sociable, married, outgoing, crowded, cooperative, agreeable, family, friendly, group, others, team, chatty, gathering, together, unity, sharing, joined, interactions, society, meeting, com- munity, popularity (e.g., ‘‘he is very talkative’’). For the non-social priming version, the 24 priming words were rebel, selﬁsh, alone, single, independent, withdrawn, secluded, uncooperative, disagreeable, independence, pri- vate, himself, individual, think, solitary, solo, detached, lone, separate, one, isolated, personal, self, unpopular (e.g. ‘‘she is often withdrawn’’). Priming task duration was approximately 15 min. Automatic Imitation and Effector Priming Control Tasks In order to obtain a reaction time (RT) measure of auto- matic imitation in a classroom/laboratory setting, we used a modiﬁed version of the two alternative choice reaction time task used in Brass et al. (2000). Short video sequences of a human hand were presented on the computer screen. The video sequences subtended approximately 6 visual angle vertically and 9 visual angle horizontally and consisted of ﬁve full-colour frames presented on a black background. The hand was presented in the vertical orientation (with the ﬁngers pointing to the right), whereas the participant rested their hand in a horizontal orientation (ﬁngers point to the computer screen) on the computer keypad; hence, response 123 Exp Brain Res (2011) 211:601–612 movements were orthogonal to stimulus postures. This feature of the design allows automatic imitation to be isolated from spatial compatibility. The Imitation and Effector Priming Control tasks com- prised a 2 9 2 factorial design with the factors Compati- bility (between participant’s ﬁnger and on screen ﬁnger: Compatible, Incompatible) and Experimental Task (Imita- tion Task, Effector Priming Control Task). For 50% of the compatible trials, the ﬁnger lifted (or changed to a green colour in the Effector Priming Control Task) was the index ﬁnger, and for 50% of the incompatible trials, the manip- ulated ﬁnger was the middle ﬁnger. There were 30 trials per trial type, 120 trials in total. Trials from the Imitation and Effector Priming Control Tasks were pseudo-ran- domized such that one trial type never occurred more than twice in a row. The duration of the Imitation plus Effector Priming Control Task was approximately 15 min. On each trial, the participant was required to place the index ﬁnger of their right hand on the letter ‘V’ on the computer keyboard and the middle ﬁnger of their right hand on the letter ‘B’ on the keyboard. Participants were told to lift the ﬁnger up as quickly as possible and then replace it on the same key. They should lift their index ﬁnger if a number 1 appeared on the screen and lift their middle ﬁnger if a number 2 appeared on the screen. The imperative stimulus (the 1 or 2) appeared between the index and middle ﬁngers and marked the onset of the response period. After the appearance of the imperative stimulus, the stimulus video was presented for 3,000 ms. The nature of the stimulus video depended on whether the trial was of the Imitation Task, or the Effector Priming Control Task. Imitation task In 50% of Imitation Task trials, the video sequence depicted an action that was compatible with the partici- pant’s required movement (e.g. the participant was required to lift the index ﬁnger, and the video showed an index ﬁnger lift); on 50% of trials, the video showed an incompatible action (e.g. the participant was required to lift the index ﬁnger and the video showed a middle ﬁnger lift). The RT difference between incompatible and compatible trials was used as an index of automatic imitation (Imita- tion Effect). Effector priming control task Stimulus videos used in the Effector Priming Control Task were not of an action. Rather, one of the ﬁngers acquired a semi-transparent green mask (Fig. 1b). On 50% of trials, the ﬁnger that changed colour was compatible with the instructed response (e.g. an index ﬁnger response was