ScienceWeek

ANIMAL BEHAVIOR: ON ANIMAL PERSONALITIES

The following points are made by S.R. Dall (Current Biology 2004 14:R470):

1) Psychologists recognize that individual humans can be classified according to how they differ in behavioral tendencies [1]. Furthermore, anyone who spends time watching non-human animals will be struck by how, even within well-established groups of the same species, individuals can be distinguished readily by their behavioral predispositions. Evolutionary biologists have traditionally assumed that individual behavioral differences within populations are non-adaptive "noise" around (possibly) adaptive average behavior, though since the 1970s it has been considered that such differences may stem from competition for scarce resources [2].

2) It is becoming increasingly evident, however, that across a range of taxa -- including primates and other mammals as well as birds, fish, insects and cephalopod molluscs -- behavior varies non-randomly among individuals along particular axes [3]. Comparative psychologists and behavioral biologists [3-5] are documenting that individual animals differ consistently in their aggressiveness, activity, exploration, risk-taking, fearfulness and reactivity, suggesting that such variation is likely to have significant ecological and evolutionary consequences [4,5] and hence be a focus for selection. From evolutionary and ecological viewpoints, non-random individual behavioral specializations are coming to define animal personalities [3], although they are also referred to as behavioral syndromes, coping styles, strategies, axes and constructs [3-5].

3) The evolution of animal personality differences is poorly understood. Ostensibly, it makes sense for animals to adjust their behavior to current conditions, including their own physiological condition, which can result in behavioral differences if local conditions vary between individuals. It is unclear, however, why such differences should persist when circumstances change. In fact, even in homogenous environments interactions between individuals can favor the adoption of alternative tactics. For instance, competition for parental attention in human families may encourage later-born children to distinguish themselves by rebelling. In the classic Hawk Dove game model of animal conflicts over resources, if getting into escalated fights costs more than the resource is worth, a stable mix of pacifist (dove) and aggressive (hawk) tactics can evolve. This is because, as hawks become common, it pays to avoid fighting and play dove, and vice versa.

4) There are, however, two ways in which evolutionarily stable mixtures of tactics can be maintained by such frequency-dependent payoffs: individuals can adopt tactics randomly with a fixed probability that generates the predicted mix in a large population; alternatively, fixed proportions of individuals can play tactics consistently. Only the latter would account for animal personality differences. It turns out that consistent hawks and doves can be favored if the outcomes of fights are observed by future opponents and influence their decisions --being persistently aggressive will then discourage fights, as potential opponents will expect to face a costly contest if they challenge for access to the resource. At least in theory, therefore, personality differences can evolve when the fitness consequences of behavior depend both on an individual's behavioral history and the behavior of other animals.

References (abridged):

1. Pervin, L. and John, O.P. (1999). Handbook of Personality. (: Guilford Press)

2. Wilson, D.S. (1998). Adaptive individual differences within single populations. Philos. Trans. R. Soc. Lond. B Biol. Sci 353, 199-205

3. Gosling, S.D. (2001). From mice to men: what can we learn about personality from animal research. Psychol. Bull. 127, 45-86

4. Sih, A., Bell, A.M., Johnson, J.C. and Ziemba, R.E. (2004). Behavioral syndromes: an integrative review. Q. Rev. Biol. in press.

5. Sih, A., Bell, A.M. and Johnson, J.C. (2004). Behavioral syndromes: an ecological and evolutionary overview. Trends Ecol. Evol. in press.

Current Biology http://www.current-biology.com

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ANIMAL BEHAVIOR: ON ANTHROPOMORPHISM

The following points are made by Clive D. Wynne (Nature 2004 428:606):

1) The complexity of animal behavior naturally prompts us to use terms that are familiar from everyday descriptions of our own actions. Charles Darwin (1809-1882) used mentalistic terms freely when describing, for example, pleasure and disappointment in dogs; the cunning of a cobra; and sympathy in crows. Darwin's careful anthropomorphism, when combined with meticulous description, provided a scientific basis for obvious resemblances between the behavior and psychology of humans and other animals. It raised few objections.

2) The 1890s saw a strong reaction against ascribing conscious thoughts to animals. In the UK, the canon of Conwy Lloyd Morgan (1852-1936) forbade the explanation of animal behavior with "a higher psychical faculty" than demanded by the data. In the US, Edward Thorndike (1874-1949) advocated replacing the use of anecdotes in the study of animal behavior with controlled experiments. He argued that when studied in controlled and reproducible environments, animal behavior revealed simple mechanical laws that made mentalistic explanations unnecessary.

3) This rejection of anthropomorphism was one of the few founding principles of behaviorism that survived the rise of ethological and cognitive approaches to studying animal behavior. But after a century of silence, recent decades have seen a resurgence of anthropomorphism. This movement was led by ethologist Donald Griffin, famous for his discovery of bat sonar. Griffin argued that the complexity of animal behavior implies conscious beliefs and desires, and that an anthropomorphic explanation can be more parsimonious than one built solely on behavioral laws. Griffin postulated, "Insofar as animals have conscious experiences, this is a significant fact about their nature and their lives." Animal communication particularly impressed Griffin as implying animal consciousness.

4) Griffin has inspired several researchers to develop ways of making anthropomorphism into a constructive tool for understanding animal behavior. Gordon Burghardt was keen to distinguish the impulse that prompts children to engage in conversations with the family dog (naive anthropomorphism) from "critical anthropomorphism", which uses the assumption of animal consciousness as a "heuristic method to formulate research agendas that result in publicly verifiable data that move our understanding of behavior forward." Burghardt points to the death-feigning behavior of snakes and possums as examples of complex and apparently deceitful behaviors that can best be understood by assuming that animals have conscious states.

5) But anthropomorphism is not a well-developed scientific system. On the contrary, its hypotheses are generally nothing more than informal folk psychology, and may be of no more use to the scientific psychologist than folk physics to a trained physicist. Although anthropomorphism may on occasion be a source of useful hypotheses about animal behavior, acknowledging this does not concede the general utility of an anthropomorphic approach to animal behavior.(1-4)

References:

1. Blumberg, M. S. & Wasserman, E. A. Am. Psychol. 50, 133-144 (1995)

2. De Waal, F. B. M. Phil. Top. 27, 255-280 (1999)

3. Mitchell, R. W. et al. Anthropomorphism, Anecdotes and Animals (State Univ. New York Press, New York, 1997)

4. Wynne, C. D. L. Do Animals Think? (Princeton Univ. Press, Princeton, New Jersey, 2004)

Nature http://www.nature.com/nature

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ON ANIMAL SELF-AWARENESS

The following points are made by Marc Bekoff (Nature 2002 419:255):

1) Researchers are interested in animal awareness because they are curious to discover what animals might know about themselves. There are, however, long-held and polarized views about the degree of self-awareness in animals. Some people believe that only great apes have "rich" notions of self --knowing who they are and/or having a "theory of mind", which means being able to infer the states of minds of others --whereas others argue that it is methodologically too difficult to address this question because animal (like human) minds are subjective and private. Many in this latter category do not attribute any sense of self to animals other than humans, and some, dismissing behavioral and neurobiological research on animal cognition, wonder whether animals are conscious of anything at all.

2) What might animals know about themselves? Most studies of animal self-awareness have been narrowly paradigm-driven. The "red spot" technique was first used by Gordon Gallup to study animal self-awareness in chimpanzees; it and variations have been used on great apes and monkeys, as well as on a few dolphins and elephants. For primates, a spot is placed on the forehead of an anesthetized individual and self-directed movements towards the spot are scored after he or she awakens and catches sight of themselves in a mirror, a high score indicating the presence of some degree of self-awareness. But in some cases, the data are derived from tests on small numbers of individuals, many of whom fail it because they do not make self-directed movements towards the spot. Those who pass the test might not be representative of wild relatives because they have had extensive human contact and previous experience with mirrors, factors that might influence their trainability and willingness to use a mirror. Those who fail the test might show some sense of 'self' in other contexts, and other individual differences might also play a role.

3) The concept of animal self-awareness remains open to different interpretations, but we will probably learn more about the mysteries of "self" and "body-ness" by using non-invasive neuroimaging techniques in combination with cognitive ethological studies. If we look at "self-awareness" as "body-awareness", we might also discover more about how animals think and the perceptual and neurobiological processes underlying various cognitive capacities. Darwin's ideas about evolutionary continuity, together with empirical data ("science sense") and common sense, caution against the unyielding claim that humans --and perhaps other great apes and cetaceans -- are the only species in which some sense of self has evolved.(1-5)

References (abridged):

1. Bekoff, M. Minding Animals: Awareness, Emotions, and Heart (Oxford Univ. Press, New York & London, 2002).

2. Bekoff, M., Allen, C. & Burghardt, G. M. (eds) The Cognitive Animal: Empirical and Theoretical Perspectives on Animal Cognition (MIT Press, Cambridge, Massachusetts, 2002); see especially essays on self-awareness by Gallup, G. G., Anderson, J. R. & Shillito, D. J.; Mitchell, R. W.; Shumaker, R. W. & Swartz, K. B.

3. Mitchell, R. W. in Handbook of Self and Identity (eds Leary, M. R. & Tangney, J.) 567 593 (Guilford, New York, 2002).

4. Reiss, D. Nature 418, 369 370 (2002).

5. Rilling, J. K. et al. Neuron 35, 395 405 (2002).

Nature http://www.nature.com/nature

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