Both motor and social-evaluative effects of imitation have been explained by the similarity of perceived and executed actions (for recent reviews, see Heyes,
2011, regarding the motor effects of imitation; and Hale & Hamilton,
2016, regarding socio-evaluative effects of imitation). But what exactly is a ‘similar’ action? While some theoretical accounts have argued that similarity is the result of a conceptual matching between two events (Jansson et al.,
2007), others suggested that similarity is the result of an associative learning process (Heyes,
2001). The present research, however, follows yet another account and adopts an ideomotor perspective on imitation (Prinz,
2005; Brass & Heyes,
2005). According to this view, actions are selected, initiated, and controlled by representations of their sensory consequences, that means, their action-effects (James,
1890; Greenwald,
1970; Hommel,
2013; for a review, Shin, Proctor, & Capaldi,
2010). Specifically, it is assumed that agents learn to associate specific movements with specific sensory effects. Importantly, the associative link between the movement pattern and the action-effect is bidirectional, which implies that the cognitive activation of the action-effect precedes the movement (Dignath, Kiesel, Frings, & Pastötter,
2020; Kühn, Keizer, Rombouts, & Hommel,
2011; van Steenbergen et al.,
2017) and that activation of the action-effect re-activates the movement pattern that caused this action-effect (e.g., Dignath, Pfister, Eder, Kiesel, & Kunde
2014 & Hommel,
2001; Kunde,
2003; Pfister & Kunde,
2013). The mental representation of actions in terms of their perceivable effects implies that ‘motor codes’ and ‘perceptual codes’ have a commensurable representational format (Hommel, Müsseler, Aschersleben, & Prinz,
2001). This common coding principle explains a similarity between perceived and performed actions with a code overlap on the representational level (Prinz,
2005).
The ideomotor framework thus provides a straightforward account of imitation because observing another person’s action should automatically activate matching movement patterns in the observer (Prinz,
2005; Wohlschläger, Gattis, & Bekkering,
2003). The stronger the overlap between the codes that represent the perceived event and the intended action, the stronger the tendency to copy the observed action. Furthermore, because both perceived changes of the body and perceived changes in the environment can guide actions (e.g., Pfister, Janczyk, Gressmann, Fournier, & Kunde,
2014a,
b; see also Pfister,
2019), imitation is not restricted to the observation of other people’s movements, but also extends to the perception of other people’s action-effects in the environment (Ondobaka, de Lange, Newman-Norlund, Wiemers, & Bekkering,
2012; Wohlschläger & Bekkering,
2002). For instance, Bekkering et al. asked pre-school children to imitate a confederate, who reached with one or both of her hands to one or both of her ears (Bekkering, Wohlschläger, & Gattis,
2000). Movements could be either ipsilateral (e.g., left hand to left ear) or contralateral (e.g., left hand to right ear). Although children were very good at touching the correct ear, they had problems choosing the appropriate hand to perform the movement. This impairment was especially pronounced for trials in which the movement of only one hand had to be imitated. According to the ideomotor view on imitation, children in this study represented their actions in terms of the location of the ear.