Interaction Studies - Volume 5, Issue 1, 2004

The study of imitation and other mechanisms of social learning is an exciting area of research for all those interested in understanding the origin and the nature of animal learning in a social context. Moreover, imitation is an increasingly important research topic in Artificial Intelligence and social robotics which opens up the possibility of individualized social intelligence in robots that are part of a community, and allows us to harness not only individual learning by the single robot, but also the acquisition of new skills by observing other members of the community (robots, humans, or virtual agents). After an introduction to the main research issues in research on imitation in various fields (including psychology, biology and robotics), we motivate the particular focus of this work, namely the correspondence problem. We describe Action Learning for Imitation via Correspondences between Embodiments (Alice), an implemented generic framework for solving the correspondence problem between differently embodied robots. Alice enables a robotic agent to learn a behavioral repertoire suitable to performing a task by observing a model agent. Importantly, the model agent could possibly possess a different type of body, e.g. a different number of limbs or joints (implying different degrees of freedom), a different height, different sensors, a different basic action repertoire, etc. Previously, in a test-bed where the agents differed according to their possible movement patterns, we demonstrated that the character of imitation achieved will depend on the granularity of subgoal matching, and on the metrics used to evaluate success. In our current work, we implemented Alice in a new test-bed called Rabit where simple simulated robotic arm agents use various metrics for evaluating success according to actions, states, effects, or weighted combinations. We examine the roles of synchronization, looseness of perceptual matching, and of proprioceptive matching by a series of experiments. Also, we study how Alice copes with changes in the embodiment of the imitator during learning. Our simulation results suggest that synchronization and loose perceptual matching allow for faster acquisition of behavioral compentencies at low error rates. Social learning (broadly construed) plays a role as a replication mechanism for behaviors and results in variability when the transmitted behavior differs from the model’s behavior, thus providing the evolutionary substrate for culture and its pre-cursors. Social learning in robotics could therefore serve as the basis for culture in societies whose members include artificial agents. We address the use of imitative social learning mechanisms like Alice for transmission of skills between robots, and give first examples of transmission of a skill despite differences in embodiment of agents involved. In the particular setup, transmission occurs through a chain, as well as emerging in cyclic arrangements of robots. These simple examples demonstrate that by using social learning and imitation, (proto-)cultural transmission is possible among robots, even in heterogeneous groups of robots.

Adopting a functionalist perspective, we emphasize the interest of considering imitation as a single capacity with two functions: communication and learning. These two functions both imply such capacities as detection of novelty, attraction toward moving stimuli and perception-action coupling. We propose that the main difference between the processes involved in the two functions is that, in the case of learning, the dynamics is internal to the system constituted by an individual whereas in the case of communication, the dynamics concerns the system composed by the perception of one individual coupled with the action of the other. In this paper, we compare the first developmental steps of imitation in three populations: typically developing children, children with autism, and robots. We show evidence of strong correlations between imitating and being imitated in typical infants and low-functioning children with autism. Relying on this evidence, the robotic perspective is to provide a generic architecture able not only to learn via imitation but also to interact as an emerging property of the system constituted by two similar architectures with a different history.

Grey parrots (Psittacus erithacus) do not acquire referential English labels when tutored with videotapes displayed on CRT screens if (a) socially isolated, (b) reward for attempted labels is possible, (c) trainers direct birds’ attention to the monitor, (d) live video feed avoids habituation or (d) one trainer repeats labels produced on video and rewards label attempts. Because birds learned referential labels from live tutor pairs in concurrent sessions, we concluded that video failed because input lacked live social interaction and modeling (Pepperberg, 1999). Recent studies (e.g. Ikebuchi & Okanoya, 1999), however, suggest that standard CRT monitor flickering could instead have prevented learning. Using an LCD monitor, we found that eliminating flickering did not enable birds to learn from video under conditions of limited social interaction. Results emphasize the role of social interaction in referential label learning and may generalize to other systems (e.g. disabled children, or possibly software and robotic agents).

This study examines the effects of sex and familiarity on Americans’ talk to dogs during play, using categories derived from research comparing mothers’ and fathers’ talk to infants. Eight men and fifteen women were videotaped whilst playing with their own dog and with another person’s dog, and their utterances were codified for features common to infant-directed talk. Women used the baby talk speech register more than men, and both men and women used this register more when interacting with the unfamiliar dog than with the familiar dog. When playing with the familiar dog, women talked more than men, and their talk was more suggestive of friendliness and having a conversation. When playing with the unfamiliar dog people used more praise, more conversational gambits, a more diverse vocabulary, and longer utterances than when playing with the familiar dog, suggesting that when playing with the unfamiliar dog, people pretended to have more of a conversation, were more attentive to appearing friendly and were less attentive to the dog’s limited understanding. Overall, however, men and women used similar forms of talk when interacting with a dog, whether familiar or not.

In recent studies of primates, the question has been raised whether competitive regimes (egalitarian versus despotic) are species-specific or should rather be considered as sex-specific. To study this problem we use an individual-oriented model called DomWorld in which artificial agents are equipped merely to group and compete. In former studies of this model, dominance style appeared to be strongly influenced by the intensity of aggression: by increasing only this intensity of aggression, a great number of the characteristics of an egalitarian society switched to those of a despotic one. Here, we investigate, using DomWorld, a competitive regime of artificial males and females that differ exclusively in their fighting capacity; males having a higher intensity of aggression and a higher initial capacity of winning, such as may be due to a male-biased sexual dimorphism. Unexpectedly it appears that, in the model, even if the intensity of aggression of males is greater than that of females, their hierarchy is still significantly weaker and thus their society less differentiated and more egalitarian than that of females. The explanation is that, due to the higher initial dominance of males (compare larger body size), single events of victory and defeat lead to less differentiation than among females. The greater the sexual difference in initial dominance between the sexes is the more egalitarian the males behave among themselves compared to the behaviour of the females among themselves. These effects are already visible during the initial phases of the hierarchical development. These results resemble findings among primates; in real primates their degree of sexual dimorphism may influence the competitive regime of each sex.