Response/Dennett: Intentional systems in cognitive ethology

that an isolated vervet monkey fails to make alarm calls does not speak to this question. Many species react silently in order to avoid detection by a predator. It is, therefore hardly that outlandish to assume the kind of "context" switches that Dennett dismisses as a behaviorist's knee-jerk interpretation of the observation that an isolated vervet monkey does not call out when it sees a leopard. To show that an organism wants to do X, it is necessary to show that there are comparable circumstances in which it elects not to do X. Suppose, for example, that two men, John and Bill, were walking through a forest and that John saw that Bill was in danger of being attacked by a snake. If Bill were John's friend, or, to put it more generally, if John did not bear strongly hostile feelings toward Bill, one would expect John to say something like, "Look out Bill! A snake's about to attack you on your left side! " Under circumstances in which John wished harm to come to Bill, John might remain silent and leave Bill at the mercy of the snake. Can a vervet monkey choose whether or not to make an alarm call? Would Tom, who notices that his rival Sam is in danger of being attacked by a snake, withhold the snake alarm call in order to eliminate Sam and thereby advance to a higher position in the dominance hierarchy of his group? Alternatively, one wonders whether Tom would refrain from making an alarm call, whose only function would be to alert vervet monkeys of a rival group of some imminent danger. ' At a more prosaic level, one might try some version of an "omission procedure" (see Sheffield 1965; Williams & Willimas 1969) to determine whether a vervet monkey could learn to refrain from making an alarm call under conditions in which that call is normally made. One might, for example, place the monkey in a situation in which an approaching leopard (as shown in a film) would be made to recede only in the absence of an alarm call. (Other monkeys would be present, but in locations that would prevent them from seeing the leopard.) Given the adaptive value of warning other members of the group of some imminent danger, it is unlikely that a vervet monkey could refrain from calling out, no matter how enticing its reward for doing so. There are at least two grounds for questioning Dennett's view that a vervet monkey can assume the role of a "Gricean" audience: the function of the audience per se and the recognition of a particular audience. Just as a foraging bee will only perform its communicative dance if it has an audience (von Frisch 1967), it may be the case that a vervet monkey (for different adaptive reasons) will only make an alarm call if it has an audience. It does not follow, however, that either creatures's communicative act is anything more than the killjoy reflex that Dennett so zealously tries to dismiss. Gricean communication not only assumes voluntary acts of communication, but an awareness oia. particular audience. The fact that a vervet monkey can discriminate calls made by a particular member of its group does not imply that the sender of a signal is addressing a particular individual of that group. How do we know that Tom is addressing Sam, as opposed to some other member of the troop occupying the same area? The absence of evidence that a vervet monkey's alarm calls are either voluntary or directed to particular individuals suggests that their communicative acts can be expressed by the following nonintentional rule: When danger,, is seen and, when within shouting distance of other vervet monkeys, produce alarm call,. In this connection, it is interesting to ask how alarm calls of vervet monkeys differ from bird calls or from other familiar examples of animal communication. In each case there is a "vocabulary" of communicative acts. Birds have been observed to sing for the following reasons: (a) to attract a mate, (b) to signal the presence of a predator, (c) to ward off conspecifics about to intrude upon their territory, and (d) to call to their young. Bees communicate the location and quality of food sites near their hives by performing an appropriate variation of the "round" or "waggle" dances. Are bird songs and bee dances intentional acts? At least in the case of bee communications, Dennett correctly rejects the concept of intentionality as superfluous. As desirable as it may be to "cast off the straightjacket of behaviorism" and seek a presentable . theoretical vocabulary," it seems counterproductive to borrow too freely from models of human intentionality when evaluating animal communication. Dennett should be lauded for devising a framework for studying a difficult and important problem. Having done so, he must await the outcome of the interesting experiments he suggests, such as the one that would employ hidden speakers to test the "disembodied" call hypothesis. My guess is that these experiments will yield results that will require a substantial rewriting of the kinds of rules needed to define the different levels of intentionality suggested by Dennett. To expect otherwise would be to misinterpret the recent successes of laboratory studies which have, with considerable rigor, demonstrated the existence of cognitive processes in animals. However, as clearly as these studies have identified various instances of animal cognition, they provide no basis for concluding that animals think like human beings (see Terrace 1982a; 1983). The most obvious reason for suspecting fundamental differences between human and nonhuman cognitive processes is the linguistic basis of human thought. Given the fundamental importance of language in human intentional systems, it seems foolhardy to ignore this fact when investigating the nature of intentional systems in nonhumans. Thus, even if it were possible to show that the alarm calls of the vervet monkey are voluntary and that a vervet monkey addresses its calls to particular members of its group, we would be left with the fascinating and nontrivial problem of defining the nonlinguistic representations of alarm calls in vervet monkey speakers and listeners.