Catalizadores de metales alcalinos y otros metales

Moore (1992) has claimed that certain serendipitous observations, or anecdotes, should be interpreted as providing evidence of imitation, providing they have been reported by suitably qualified observers. Sections 1.1.1 and 1.1.2 review examples of prima facie anecdotes o f behavioural concordance reported by scientists. Only anecdotes describing behavioural concordance for non-object-directed movements were selected because these cases could not

be accounted for in terms of socially mediated effects based upon response correlated inanimate stimuli. In Section 1.1.3 Moore's claim is evaluated with reference to these examples.

7.7.7. A monkey lapping milk

One published serendipitous observation related to an unusual consummatory behaviour (Ball, 1938). Pepper, a juvenile rhesus monkey that had been raised with a kitten, was observed in a pet shop window drinking milk in the same lapping manner as a cat, rather than the sucking method characteristic of monkeys. Thus, the topography o f this monkey's drinking was reported to be more similar, in a distinctive way, to that o f an observed cat than that o f a conspecific. However, the extent to which this observation provides convincing evidence of inter-species imitation rests upon two assumptions which are hard to assess. First, is the assumption that this behaviour may not have become adopted by chance. On the one hand, drinking behaviour is likely to be fairly genetically constrained, and therefore tend to be species typical (this is reflected in Ball's insistence that, in over 600 monkeys encountered by colleagues, lapping had never been observed). On the other hand, the bias to report anecdotes of interesting effects leads to a sampling bias that may overestimate even the most unlikely of events; Pepper may have lapped his milk because he was one of a small proportion of monkeys that spontaneously exhibit this technique and other lapping monkeys have not been reported, or remembered by scientists, because they lack such a cute story to explain their behaviour. The second assumption is that Pepper had the capacity to exhibit either drinking technique. It is possible that Pepper's drinking method was enforced: He had been housed with a kitten because of repeated serious attacks from his father, which may possibly have damaged the musculature required for sucking.

7.7.2. Chimpanzees and signing

Some other anecdotes that have been claimed to indicate imitation have been the serendipitous product of attempts to teach chimpanzees language using American Sign Language (ASL). ASL is comprised of gestural signs not directed at objects or specific locations in the environment, so the reproduction of signs is unlikely to be due to a, non-

imitative, social effect based upon a representation of the inanimate world (such as stimulus enhancement). In his re-analysis of data from Project Nim (e.g.. Terrace, Petitto, Sanders, and Bever, 1979), Sanders (1985) concluded that many of Nim's gestural utterances were an immediate reproduction of those of a trainer, and that these were likely to have been due to "imitation". However, immediate reproductions of signs may have been specific trained responses resulting from the differential reinforcement of matching behaviour (matched dependent behaviour). This alternative account is supported by the observation that "Nim could obtain rewards by imitating his trainer's prior signs" (Sanders, 1985, p.209).

ASL was also used by Gardner & Gardner (1969) in their attempt to teach language to the chimpanzee Washoe. Following the imitation set series (Hayes & Hayes, 1952, described in Section 2.1), one of the training methods tried was the imitation of signs on command. Although rewards were provided whenever a demonstrated sign was seen to be reproduced, this did not prove to be a successful method of introducing signs into Washoe's repertoire. Potentially more impressive was the acquisition of two signs, "toothbrush" and "flower", after seeing only demonstrations of the signs in appropriate contexts and with no formal training; differential reinforcement of matching behaviour is unlikely to account for the acquisition of these signs. However, there are reasons to limit the confidence with which these behaviours are taken to be imitative copies. Gardner and Gardner accepted that it is a real possibility that there was a bias, on the part of Washoe's "devoted companions" (p. 667), to report appropriate signing. This is compounded by the fact that both signs are head directed, so similar behaviours are known to have a high baseline rate o f occurrence among apes (Diamond & Harries, 1984). In addition, the sign for toothbrush is rubbing of the front teeth with an index finger. The reported spontaneous use of the sign for toothbrush in a bathroom may have simply been Washoe's attempt to clean her teeth, without using a toothbrush, in a context in which cleaning teeth tended to occur.

In a further report of the acquisition of ASL with no formal training from human caregivers, it was suggested that an infant chimpanzee, Loulis, acquired a vocabulary o f 51 signs following demonstrations of signing by his adoptive mother, Washoe (Pouts et al., 1989). The human observers took care not to sign in Loulis' presence. It was reported that some new signs were first observed after being modelled by Washoe: "As Washoe was signing DRINK, Loulis watched her and signed DRINK, himself (p. 290). However, it is impossible

to assess whether Loulis' signing may have been contingent upon having seen a dem onstration because the frequency of new signs that did not follow a demonstration by W ashoe was not reported. Furthermore, because the chimpanzees were not continuously observed, the first sighting of a novel sign need not be the occasion on which that sign was acquired. Other processes were likely to have accounted for many o f the signs. For example, Washoe was observed moulding Loulis' limbs into the shapes of certain signs. She also was reported to have physically indicated the part of Loulis' body to which a new sign should be directed. W ithout continuous observation, tuition cannot be ruled out as an alternative explanation for the acquisition all of the acquired signs, including that for "drink". It is possible that Washoe, not Loulis, was sensitive to the correspondence between observed and executed signs. Even though such a sensitivity could be accounted for by specific

correspondences learned during Washoe's formal training, this anecdote is striking because examples o f tuition by animals are rare and controversial (Premack, 1991).

1.1.3. Problems with anecdotes

Although the observations reported in this section conform to Moore's (1992, pp 236 - 237) criteria of good anecdotal evidence, none of them provides conclusive evidence of imitation: It has been possible to provide non-imitative accounts of these observations that were reported on "first hand accounts by competent observers", and, at first glance, seemed "sufficiently well-defined to permit unambiguous perception". Perhaps anecdotal data can never be conclusive. A number of methodological issues that have a particular impact upon anecdotal evidence have been revealed. Behaviour concordance must be assessed on the reported subjective Judgement of similarity in response topography, with target topographies not under the observer's control, that are often made by researchers uncertain about their own impartiality (e.g., Gardner and Gardner, 1969). A publication bias that favours positive anecdotal evidence makes it difficult to rule out chance factors for any unambiguous concordance (e.g.. Ball, 1938). A failure to consider the history of the animal prior to the observation could result in the overlooking of non-imitative factors which might result in behavioural concordance, such as (1) physiological constraint to exhibit the target behaviour (e.g.. Ball, 1938), (2) provision of positive reinforcement for matching behaviour (or matched dependent behaviour, e.g., Sanders, 1985), (3) physical manipulation into the target behaviour ("moulding", "co-action" or "putting through", Moore, 1992; e.g., Fouts et al.,

1989). Anecdotal reports of behavioural concordance for object directed movements (e.g., Russon & Galdikas, 1993, 1995) tend to be subject to an even larger range of alternative explanations (Whiten & Ham, 1992).