Abstract: We cannot solve questions about imitative learning without knowing what motivates animals to copy others. Imitative capacities can be expected to be most pronounced in relation to situations and models of great social significance. Experimental research on nonhuman primates has thus far made little effort to present such situations and models.
 

On several occasions, we have seen other apes mimic the victim's desperate situation. For example, the last time this happened I approached to assist but received threatening barks from both the mother and the alpha male. As a result, I just stood next to the fence and watched. One older juvenile came over to reconstruct the event. Looking me in the eyes, she inserted her finger into the mesh, slowly and deliberately hooking it around, and then pulled as if she, too, had gotten caught. Then two other juveniles did the same at a different location, pushing each other aside to get their fingers in the same tight spot they had selected for this game. Long ago these juveniles themselves may have experienced the situation for real, but here their charade was prompted by what had happened to the infant.

I wonder where this behavior would fall under the usual classifications of imitation: no problem was being solved, no goal was being copied, and no reward was procured. Manifestly fascinated by the infant's predicament, the juveniles' imitation seemed emotionally charged. In discussions of social cognition, I find attention to motivation, emotional or otherwise, sorely missing. Experiments often test responses to different species in peculiar situations, such as a person with a bag over his head (Povinelli et al. 1990) or a person manipulating a puzzle box (Whiten et al. 1996). The animal subjects are asked not only to cross a species barrier, but also to select the relevant stimuli from among many unfamiliar ones.

I applaud the authors of the target article for attempting to steer away from the all-or-nothing classifications that have until recently dominated the imitation debate and for studying imitation in daily life rather than in isolated experimental trials. Their distinction between action-level and program-level imitation seems extremely useful, even though I remain unconvinced by some of the examples in support of the latter capacity The case for gorillas would be stronger if individual learning could be ruled out. Program-level transmission would predict the existence of different populations in which the majority of gorillas process the same plant species by means of different action sequences. Do such populations exist?

Orangutans stringing up hammocks and washing dishes present a more convincing case. It seems unlikely that these apes received training for actions that humans would certainly rather not have them perform, such as siphoning fuel from a drum. The fact that this sort of imitation occurs in orangutans living with humans is significant. These apes probably sympathize with humans, as defined by Humphrey (1976, p. 313): "By sympathy I mean a tendency on the part of one social partner to identify himself with the other and so make the other's goals to some extent his own."

If sympathy varies with emotional closeness to the model, this has serious consequences for claims about imitation, or the absence thereof, in human-animal experiments. For example, instead of ascribing to "enculturation" rare forms of imitation of humans by human-reared apes, as Tomasello et al. (1993) have done, it is entirely possible that all that human-rearing does is affect the range of identification objects. Animals probably identify the easiest with the species they know best. Remember Darwin's (1871) story of dogs cleaning themselves in cat-like fashion after having been reared by cats. Perhaps these dogs "thought" they were cats, in the sense that they had been imprinted on them. In the same way, rehabilitant orangutans and language-trained bonobos may see themselves as partly human. Rather than transforming cognitive capacities - as implied by the concept of "enculturation" - the simpler view is that rearing by another species increases the willingness to imitate this species.

The capacity to identifier with others is widespread in the animal kingdom, as are basic forms of sympathy and empathy (de Waal 1996). Hence we should not hesitate to include in the imitation debate species such as octopi (Fiorito & Scotto 1992), hamsters (Previde & Poli 1996), guppies (Dugatkin & Godin 1992), and birds (Akins & Zentall 1996; Lefebvre & Giraldeau 1994). In addition, we should focus on the most salient stimuli for each species: observational learning is probably most fully expressed in relation to this class of stimuli. A group mate in distress, or engaged in a sexual or aggressive encounter may draw more intense and precise attention than the sight of a human experimenter with a new contraption.

It follows that we should look beyond what animals do in tightly controlled laboratory tests: convergent evidence from natural or naturalistic settings is essential to the study of social cognition (de Waal 1991). Even if Byrne & Russon need to do more research before their conclusions can be accepted, their attention to spontaneous behavior is refreshing and essential for a full picture of animal imitative capacities.

Frans B. M. de Waal
Living Links Center
Yerkes Regional Primate Research Center and Psychology Department
Emory University Atlanta, GA 30329
dewaal@rmy.emory.edu

 
References

Akins, C. K. & Zentall, T. R. [1996]. Imitative learning in male Japanese quail using the two-action method. Journal of Comparative Psychology 110, 316-320.

Byrne, Richard W. and Anne E. Russon [1998]. Learning by imitation: A hierarchical approach. Behavioral and Brain Sciences 21, 667-721. (The target article for de Waal's commentary.)
Darwin, Charles [1871]. The Descent of Man.

de Waal, F. B. M. [1991]. Complementary methods and convergent evidence in the study of primate social cognition. Behaviour 118, 297-320.

de Waal, F. B. M. [1996]. Good natured: the origins of right and wrong in human and other animals. Havard UP.

Dugatkin, L. A.  & Godin, J. J.  [1992]. Reversal of female mate choice by copying in the guppy. Proceedings of the Royal Society of London 249, 179-184.

Fiorito, G.  & Scotto, P.  [1992]. Observational learning in Octopus vulgaris. Science 256, 545-547.

Humphrey, Nick K. [1976]. The social function of the intellect. In Growing points in ethology. ed. P.P. G. Batson, & R. A.Hinde. CUP.

Lefebvre, A. & Giraldeau, L. [1994]. Cultural transmission in pigeons is affected by the numbers of tutors and bystanders present. Animal Behaviour 47, 331-337.

Previde, E. P. & Poli, M. D.  [1996]. Social learning in the golden hamster. Journal of Comparative Psychology 110, 203-208.

Provinelli, D. J., Boyson, S. T. & Nelson, K. E. [1990]. Inferences about guessing and knowing by chimpanzees. Journal of Comparative Psychology 104: 203-210.

Tomasello, M., Kruger, A. C. & Ratner, H. H. [1993] Cultural learing. Behavioral and Brain Sciences 16, 495-552.

Whiten, A., Custance, D., Gomez, J.-C., Texeidor, P. & Bard, K. A. [1996]. Imitative learning of artificial fruit processing in children and chimpanzees. Journal of Comparative Psychology 110, 3-14.