Cecilia Heyes

Causes and consequences of imitation

Recent behavioural and neuroscientific research concerning imitation has revealed evidence of experience-dependent imitation in chimpanzees and birds, wide ranging imitation deficits in autism, and unintentional imitation in adult humans. This review examines these findings and also evaluates evidence of neonatal imitation and intentional imitation in infancy, and evidence suggesting that the left inferior frontal gyrus is specialized for imitation. At the theoretical level, the empirical findings support the view that the perceptual-motor translation that is a unique and defining property of imitation depends primarily on direct links between sensory and motor representations established through correlated experience of observing movements and carrying them out.

Imitation: Is cognitive neuroscience solving the correspondence problem?

Imitation poses a unique problem: how does the imitator know what pattern of motor activation will make their action look like that of the model? Specialist theories suggest that this correspondence problem has a unique solution; there are functional and neurological mechanisms dedicated to controlling imitation. Generalist theories propose that the problem is solved by general mechanisms of associative learning and action control. Recent research in cognitive neuroscience, stimulated by the discovery of mirror neurons, supports generalist solutions. Imitation is based on the automatic activation of motor representations by movement observation. These externally triggered motor representations are then used to reproduce the observed behaviour. This imitative capacity depends on learned perceptual-motor links. Finally, mechanisms distinguishing self from other are implicated in the inhibition of imitative behaviour.

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

A core requirement for imitation is a capacity to solve the correspondence problem; to map observed onto executed actions, even when observation and execution yield sensory inputs in different modalities and coordinate frames. Until recently, it was assumed that the human capacity to solve the correspondence problem is innate. However, it is now becoming apparent that, as predicted by the associative sequence learning model, experience, and especially sensorimotor experience, plays a critical role in the development of imitation. We review evidence from studies of non-human animals, children and adults, focusing on research in cognitive neuroscience that uses training and naturally occurring variations in expertise to examine the role of experience in the formation of the mirror system. The relevance of this research depends on the widely held assumption that the mirror system plays a causal role in generating imitative behaviour. We also report original data supporting this assumption. These data show that theta-burst transcranial magnetic stimulation of the inferior frontal gyrus, a classical mirror system area, disrupts automatic imitation of finger movements. We discuss the implications of the evidence reviewed for the evolution, development and intentional control of imitation.

What Is the Significance of Imitation in Animals

Publisher Summary This chapter explains the significance of imitation in animals. The greatest challenge for any theory of the cognitive mechanisms of imitation is to explain imitation of “perceptually opaque” actions, those actions that yield dissimilar sensory inputs when observed and executed. The reason of this difficulty is discussed in the chapter. The chapter also distinguishes two types of theory of imitation, transformational and associative, in terms of the way in which they attempt to meet this challenge. Transformational theories suggest that most of the information necessary to achieve a behavioral match is generated internally by complex cognitive processes, whereas associative theories claim that this information is derived principally from experience. These theories delineate plausible alternative accounts of the psychological mechanisms of imitation, but they do not provide a satisfactory framework for empirical inquiry because each theory either does not make testable predictions or is inconsistent with what is already known about the conditions of imitation. The associative sequence learning (ASL) theory is discussed and the significance of imitation in animals with respect to culture rather than cognition is also discussed.

Intact automatic imitation of human and robot actions in autism spectrum disorders

The existence of a specialized imitation module in humans is hotly debated. Studies suggesting a specific imitation impairment in individuals with autism spectrum disorders (ASD) support a modular view. However, the voluntary imitation tasks used in these studies (which require socio-cognitive abilities in addition to imitation for successful performance) cannot support claims of a specific impairment. Accordingly, an automatic imitation paradigm (a ‘cleaner’ measure of imitative ability) was used to assess the imitative ability of 16 adults with ASD and 16 non-autistic matched control participants. Participants performed a prespecified hand action in response to observed hand actions performed either by a human or a robotic hand. On compatible trials the stimulus and response actions matched, while on incompatible trials the two actions did not match. Replicating previous findings, the Control group showed an automatic imitation effect: responses on compatible trials were faster than those on incompatible trials. This effect was greater when responses were made to human than to robotic actions (‘animacy bias’). The ASD group also showed an automatic imitation effect and a larger animacy bias than the Control group. We discuss these findings with reference to the literature on imitation in ASD and theories of imitation.

Imitation in Infancy: The Wealth of the Stimulus.

Imitation requires the imitator to solve the correspondence problem--to translate visual information from modelled action into matching motor output. It has been widely accepted for some 30 years that the correspondence problem is solved by a specialized, innate cognitive mechanism. This is the conclusion of a poverty of the stimulus argument, realized in the active intermodal matching model of imitation, which assumes that human neonates can imitate a range of body movements. An alternative, wealth of the stimulus argument, embodied in the associative sequence learning model of imitation, proposes that the correspondence problem is solved by sensorimotor learning, and that the experience necessary for this kind of learning is provided by the sociocultural environment during human development. In a detailed and wide-ranging review of research on imitation and imitation-relevant behaviour in infancy and beyond, we find substantially more evidence in favour of the wealth argument than of the poverty argument.

Reflections on self-recognition in primates

Abstract Abstract. Evidence that apes touch head marks more in the presence of a mirror than in its absence have been taken to indicate that, unlike monkeys, they are capable of self-recognition and have a self-concept. Both of these conclusions are challenged. First, variance in mark-touching behaviour may be due, not to mirror-presence, but to the effects of anaesthetic recovery on species with a high baseline frequency of self-directed behaviour. Second, evidence of species differences in mirror-guided body inspection could not be explained in terms of the presence or absence of a self-concept. Since monkeys can avoid colliding with objects, they must possess the only kind of self-concept necessary for mirror-guided body inspection; i.e. the capacity to discriminate feedback from other sensory input. Rather than implying a self-concept, mirror-guided body inspection involves the use of novel, displaced visual feedback to guide action.

Through the looking glass: Counter-mirror activation following incompatible sensorimotor learning

The mirror system, comprising cortical areas that allow the actions of others to be represented in the observer’s own motor system, is thought to be crucial for the development of social cognition in humans. Despite the importance of the human mirror system, little is known about its origins. We investigated the role of sensorimotor experience in the development of the mirror system. Functional magnetic resonance imaging was used to measure neural responses to observed hand and foot actions following one of two types of training. During training, participants in the Compatible (control) group made mirror responses to observed actions (hand responses were made to hand stimuli and foot responses to foot stimuli), whereas the Incompatible group made counter‐mirror responses (hand to foot and foot to hand). Comparison of these groups revealed that, after training to respond in a counter‐mirror fashion, the relative action observation properties of the mirror system were reversed; areas that showed greater responses to observation of hand actions in the Compatible group responded more strongly to observation of foot actions in the Incompatible group. These results suggest that, rather than being innate or the product of unimodal visual or motor experience, the mirror properties of the mirror system are acquired through sensorimotor learning.

Motor learning by observation: Evidence from a serial reaction time task

This study sought evidence of observational motor learning, a type of learning in which observation of the skilled performance of another person not only facilitates motor skill acquisition but does so by contributing to the formation of effector-specific motor representations. Previous research has indicated that observation of skilled performance engages cognitive processes similar to those occurring during action execution or physical practice, but has not demonstrated that these include processes involved in effector-specific representation. In two experiments, observer subjects watched the experimenter performing a serial reaction time (SRT) task with a six-item unique sequence before sequence knowledge was assessed by response time and/or free generation measures. The results suggest that: (1) subjects can acquire sequence information by watching another person performing the task (Experiments 1-2); (2) observation results in as much sequence learning as task practice when learning is measured by reaction times (RTs) and more than task practice when sequence learning is measured by free generation performance (Experiment 2, Part 1); and (3) sequence knowledge acquired by model observation can be encoded motorically—that is, in an effector-specific fashion (Experiment 2, Part 2).

Making mirrors: Premotor cortex stimulation enhances mirror and counter-mirror motor facilitation

Mirror neurons fire during both the performance of an action and the observation of the same action being performed by another. These neurons have been recorded in ventral premotor and inferior parietal cortex in the macaque, but human brain imaging studies suggest that areas responding to the observation and performance of actions are more widespread. We used paired-pulse TMS to test whether dorsal as well as ventral premotor cortex is involved in producing mirror motor facilitation effects. Stimulation of premotor cortex enhanced mirror motor facilitation and also enhanced the effects of counter-mirror training. No differences were found between the two premotor areas. These results support an associative account of mirror neuron properties, whereby multiple regions that process both sensory and motor information have the potential to contribute to mirror effects.