Dittrich WH (1992) Behavioral and Brain Sciences 15, 152
University of Exeter, Department of Psychology, Washington Singer Labs, Exeter EX4
BBS Commentary on
Cheney, D.L. & Seyfarth, R.M. (1990): How monkeys see the world. University of Chicago Press.
Evolution of intelligence: The starting point for most modern theories of intelligence in primates is the
assumed discrepancy between their performance on learning tests in the laboratory and their 'greater
intelligence when dealing with each other'(p.256; cf. 'social intelligence hypotheses'). C&S emphasize
this discrepancy while supporting a more general version such as Rozin's (1976) inaccessibility model
of intelligence within different domains. They characterize their approach as a practical, functional
perspective, but in the end it seems to be more a utilitarian, than an evolutionary functional approach.
I would argue that their approach to intelligence is in fact a version of the 'sufficiency argument ' first
introduced by Simon (1981) in the context of AI. The essence of this approach is that intelligent creatures
must be able to represent the important aspects of their environments in their knowledge of the world.
Within a functioning monkey society the representational requirements of this knowledge are probably
so severe that only a few modes of knowledge can meet them. Therefore a demonstration that a
particular mode of intelligence can support the wide range of representations monkeys obviously do use
is powerful evidence for that mode as the appropriate model of monkeys' intelligence. What C&S
arguing, in effect is due to the dominance of social affairs that the social mode of intelligence has the
required representational power. Nevertheless, it should be stated that the notion of intelligence is in fact
too vague to be the core of an evolutionary approach to cognitive behaviour or cognition. Even human
intelligence is not a homogenous scientific concept (Howe 1988). Primate intelligence can be divided into
several relatively autonomous abilities, e.g. perceptual or motor skills, communicative or social
competence, foraging knowledge, categorization or classification performance. Intelligence has evolved
independently in different taxonomic groups and is neither a cognitively homogeneous nor a phylogenetically homologous behavioural function. Intelligent behaviour evolved because animals had to cope with
the increasing environmental complexity resulted from evolutionary diversification. The increasing
instability of animal/environment interactions could only be handled by reducing this complexity
internally, that is to say cognitively (duplicate complexity hypotheses). On this basis, the critical
evolutionary pressure could be social, but it could be any other relevant ecological factor. In the
Cercopithecidae, as opposed to birds or other primate groups, it may have been mainly a social factor.
But it seems to be of little value to stress one factor of intelligence (e.g. social knowledge) against others
(e.g. nonsocial knowledge). Instead, we should take a functional systemanalytic approach (Dittrich 1988;
1990), that is we should take all relevant, both proximate and ultimate, factors into account to understand
behavioural processes. Such a view implies that intelligence did not evolve domain-specific. On the
contrary, domain-specificity seems to be the result of particular adaptation processes and not the starting
point. In practice, the different selection pressures tending to produce intelligence are linked, so any
claim that the evolution of intelligence can be explained on the basis of a single factor is highly
Concept formation: Surprisingly, C&S don't mention any of the important studies of the structural basis
of the assumed mentalistic processes called intelligence. Admittedly, though it has proved extremely
difficult to isolate the comparatively simple but measurable mental processes which are assumed to form
the building blocks of more general knowledge. But some causal investigations have been done (cf.
Griffin 1982; Mackintosh 1983; Weiskrantz 1985; Baddeley 1986). C&S gave no attention to key areas
such as vision or memory and they are highly critical of experimental laboratory tests e.g. in the area of
animal 'concepts'. Certainly, the results of experiments on concept formation are controversial, but that
is typical in areas under intensive research. There is a strong body of positive and reliable results
highlighting different parts of the cognitive process of concept formation (e.g. Rosch & Lloyd 1978; Smith
& Medin 1981; Herrnstein 1985; Lea & Ryan 1990; Perrett et al. in press). C&S correctly emphasize the
point that sometimes the ecological context in these studies is missing. This is an essential point not
because ecology is en vogue but because it is a precondition for understanding the idea of 'concepts' to
grasp functional relations between external objects and internal cognitions. To understand the mind of
monkeys C&S look at the monkeys' immediate environment, but ignore the organization of cognitive
components as the basis for conceptual order. Laboratory experiments on concept formation, perhaps,
do the reverse. But, ecological factors are ultimatively insufficient to understand the diversity of monkeys'
ability to categorize and classify (Dittrich 1988). Cognitive factors such as hypotheses (Gregory 1980)
or schemata (Lorenz 1975) are operating in perception and memory, and they play an important role in
goal-achieving behaviour. However, the reference points of mental representations are not necessarily
the goals to which behaviour is oriented or which it is intended to reach (McFarland 1989). According to
the 'connection principle' formulated by Searle (1990), intention and its communication is bound to
consciousness, which monkeys probably lack. Thus, is the monkey's lack of what Searle calls aspectual
shape the reason why mind-reading between monkeys will finally remain in the realms of science fiction?
Philosophy of science: Different approaches to primate ethology give different perspectives and different
perspectives lead to different observations. But different does not imply better. Does the utilitarian
cognitive viewpoint proposed by C&S offer a broader or more realistic perspective for observation and
data collection than the more cautious classical approach? The intentional perspective may be more
convenient for describing primate behaviour, but it does not necessarily lead to a better understanding
of what is happening in the monkey's mind. The reality of the monkey's mind or the 'how to be like a
monkey' is forever inaccessible but this is not, as C&S claim, an empirical matter, but a logical one. The
achievable aim is to understand the effects and causes of monkeys' behaviour, including the roles played
by their cognitions and the underlying physiological structures. The concept of intelligence is purely
descriptive; it has not been established as a valid explanatory concept in scientific psychology (Howe
1988). The same holds for the concepts of mind, belief and intention. The founders of ethology were
acutely aware of the trap of believing that by describing animals' behaviour they were providing reasons
for the behaviour; a necessary distinction which is often lost in cognitive science when we account for
behaviour in such terms as belief, desire, goal-orientation or intention. Can we transfer traditional
ethologists' wisdom to modern primatology? Or will it turn out that human, scientific intelligence is
I am grateful Ian Gordon, Michael Howe, Catriona Ryan and especially Stephen Lea for helpful
discussions. Preparation was supported by the Alexander von Humboldt-Foundation through a Feodor
Lynen Fellowship held by the author.
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