The evolution of imitation: what do the capacities of non-human animals tell us about the mechanisms of imitation?

Abstract

In this paper, we review reports and present new empirical data from studies with marmosets and dogs that address the correspondence problem of imitation research. We focus on the question of how it is possible to transform visual information into matching motor acts. Here, the important issue is not the learning of a complex skill, but determining the copying fidelity of animals at different levels of behavioural organization. As a theoretical framework, we suggest a classification in terms of movement, action and result, which shows a positive relationship between the organizational level of imitation and matching degree. While the monkey studies have provided evidence of very precise copying of movements and, to a lesser degree, of behaviours, the dog studies have provided evidence of action copying and the reproduction of results. In a Do-as-I-do study, a dog attempted to reproduce the results of demonstrated object manipulations at the expense of movement details. Transitive actions were more easily replicated than intransitive ones, and familiarity of actions had a major influence. The discussion of these findings addresses the question of the neuronal mechanisms underlying imitation and whether a single mechanism is sufficient to explain the different levels of copying fidelity.

Imitation as an inheritance system

“…Whether or not some correspondence mechanisms develop independently of experience, the results reported by Catmur et al (2007Catmur et al ( , 2009) strongly suggest that existing correspondence mechanisms can be added to, or adapted through, associative learning from individual experience. Rizzolatti argues that novel actions can be incorporated into the pre-existing mirror system (Rizzolatti 2005;Huber et al 2009), whereas Catmur et al argue that all correspondence mechanisms are acquired by experience. Either way, if it is right that the range of behaviours that can be passed on by imitation is not limited to some innate library of perceptuo-motor mappings, then the putative imitation-based inheritance system has greater evolutionary power, and its capacity to explain the exceptionalism of human culture is correspondingly increased.…”

“…Voelkl & Huber (2007) went on to do a detailed movement analysis of marmoset behaviour, using a discriminant analysis classifier, which suggested that observers precisely copied the movement patterns of the models they had observed. Great apes can also be trained to copy novel actions; from humans by learning the general rule 'do as I do' and extending it to novel actions; as, it seems, can dogs (both summarized by Huber et al 2009). …”

“…Similarly, primates can emulate an observed goal using a novel means, other than the one they have observed (Tennie et al 2009). Dogs, too, seem to imitate selectively to achieve the best functional fit between actions and goal (Range et al 2007;Huber et al 2009). These are perfectly rational tendencies, from the perspective of individual learning.…”

Associative sequence learning: the role of experience in the development of imitation and the mirror system

“…The ASL theory, in contrast, predicts that imitation is likely to occur in a variety of species, to the extent that the sensorimotor experience of the imitated actions was available during development. While early studies of imitation in non-human animals were beset with methodological problems (see Tomasello et al 1987;Whiten & Ham 1992), recent data (see also Huber et al 2009) provide compelling evidence for imitation of simple movements across a range of species, including chimpanzees (Custance et al 1995;Whiten et al 1996Whiten et al , 2004, marmosets (Bugnyar & Huber 1997;Voelkl & Huber 2007), dogs (Slabbert & Rasa 1997;Range et al 2007) and several bird species (Lefebvre et al 1997;Campbell et al 1999;Mui et al 2008). For example, dogs will perform a paw-press action to obtain a food reward, rather than the usually preferred mouth action, after observing a demonstrator dog using this action (Range et al 2007).…”

Automatic imitation in dogs

“…Single case studies have found 'functional matching' of human actions (e.g. reproducing the object-related effects of an observed action), but were ambiguous with respect to body movement imitation [20,21]. Similarly, Miller et al [22] showed that dogs that have seen a conspecific pushing a screen door to the right or left are more likely than controls to push the door in the same direction as their demonstrator.…”