602 1999; Lakin and Chartrand 2003). It has been demonstrated that when people are not aware that their behaviour is being copied, being mimicked increases rapport (Chartrand and Bargh 1999), feelings of closeness (Ku¨hn et al. 2010), altruistic behaviour (van Baaren et al. 2004) and trust (Bailenson and Yee 2005). In a study where half the par- ticipants were mimicked by a confederate and half were not, participants who were mimicked reported liking the confederate more than those who were not (Chartrand and Bargh 1999). In another study, waitresses who were instructed to mimic their customers received bigger tips than those who were instructed not to mimic (van Baaren et al. 2003a). Thus, a range of studies suggests that unconscious mimicry is linked to increased positive social attitudes. A number of studies suggest that the converse rela- tionship—that positive social attitudes increase uncon- scious mimicry—is also true. Early research suggested that among romantic couples, there is a correlation between the amount of rapport they feel with each other and the amount of imitation that takes place during their interactions (Bernieri 1988; Lafrance 1979, 1982; Lafrance and Broadbent 1976). Van Baaren et al. varied self-construal orientation and found that participants with either a tem- porarily induced, or chronic, dominant interdependent self- construal were more likely to match the behaviours of a confederate than those with an independent self-construal (van Baaren et al. 2003b). Recently Leighton et al. (2010) demonstrated that unconscious priming of positive social attitudes increases imitative behaviour in adults. In the study by Leighton et al., each participant completed two tasks: ﬁrst, a social attitude priming task and then an automatic imitation task. For the priming task, participants formed sentences from sets of words that included pro- social, neutral or anti-social terms (three groups). In each trial of the automatic imitation task, participants were required to perform a pre-speciﬁed hand movement (open or close) as soon as they saw a hand on a computer screen begin to move. The hand movement stimulus was either the same as the pre-speciﬁed response (compatible trials, e.g. open stimulus and open response) or the hand movement stimulus was the opposite of the pre-speciﬁed response (incompatible trials, e.g. close stimulus and open response). Although participants are not required to imitate, imitative responses (compatible trials) are consistently faster than non-imitative responses (incompatible trials; Brass et al. 2000; Heyes et al. 2005). The magnitude of this Imitation Effect was calculated as the reaction time difference between incompatible and compatible trials. Leighton et al. found that participants primed with pro-social words showed a larger Imitation Effect than those primed with anti-social words, and the neutral group showed an intermediate Imitation Effect. 123 Exp Brain Res (2011) 211:601–612 Although the psychological and neural mechanisms by which social attitudes modulate imitation are currently unknown, a number of studies suggest that the neural mechanisms that underlie the representation of others are involved in ‘top-down’ control of automatic imita- tive responses (Brass et al. 2003, 2005; Spengler et al. 2010a, b). In a study using functional Magnetic Resonance Imaging (fMRI), Brass et al. (2005) demonstrated that inhibition of imitation, in contrast to inhibition of non- imitative automatic responses (Stroop Task), activated both the medial prefrontal cortex (MPFC) and temporo-parietal junction (TPJ). The MPFC and TPJ are part of the ‘social brain’ (Brothers 1990; Frith 2007; Frith and Frith 2010), a network of brain areas that is active when we process social information, in particular when we represent the mental states (intentions, desires, beliefs) of others (‘theory of mind’). In addition to recruiting common neural areas, two recent studies suggest that the control of imitation and the representation of others are functionally associated. Spen- gler et al. (2010b) showed that the degree to which par- ticipants were able to inhibit imitative responses was correlated with performance on a behavioural theory of mind task and also with activity in the MPFC and TPJ when participants performed a theory of mind task whilst being scanned. Furthermore, patients with lesions to the MPFC and TPJ show impaired performance on theory of mind tasks, and the extent of their impairment correlates with their degree of impairment on an imitation inhibition task (Brass et al. 2003). Therefore, these studies suggest that control of imitation and the representation of others share a component process, and that parts of the social brain may be responsible for mediating imitation as a result of social priming. Adolescence is an important period in the development of social cognition and the social brain (for review see Blakemore 2008, 2010). This period can be characterized by changes in self-awareness (Sebastian et al. 2008; Harter 1990), in social behaviour (Brown 2004), and in responses to social situations (Sebastian et al. 2010; Hillebrandt et al. in press). For instance, Sebastian et al. (2010) showed that self-reported affective responses to social exclusion are signiﬁcantly greater for adolescents compared to adults. In addition to changes in social attitudes and behaviours, the adolescent years are also a time when many structural and functional changes are taking place in the brain. Both cellular (Huttenlocher 1979) and MRI (Giedd et al. 1999; Sowell et al. 1999; Paus 2005) studies suggest that some brain regions, including parts of the social brain, are still anatomically developing well into the adolescent years. For example, a recent developmental MRI study that measured cortical thickness in a sample of 375 participants aged 4–21 found that MPFC is one of the latest regions to mature, with a peak in cortical thickness at around age 14 years