How are we able to understand and anticipate each other in everyday life, in our daily interactions? Through the use of such "folk" concepts as belief, desire, intention, and expectation, asserts Daniel Dennett in this first full-scale presentation of a theory of intentionality that he has been developing for almost twenty years. We adopt a stance, he argues, a predictive strategy of interpretation that presupposes the rationality of the people - or other entities - we are hoping to understand and predict.These principles of radical interpretation have far-reaching implications for the metaphysical and scientific status of the processes referred to by the everday terms of folk psychology and their corresponding terms in cognitive science.While Dennett's philosophical stance has been steadfast over the years, his views have undergone successive enrichments, refinements, and extensions. "The Intentional Stance" brings together both previously published and original material: four of the book's ten chapters - its first and the final three - appear here for the first time and push the theory into surprising new territory. The remaining six were published earlier in the 1980s but were not easily accessible; each is followed by a reflection - an essay reconsidering and extending the claims of the earlier work. These reflections and the new chapters represent the vanguard of Dennett's thought. They reveal fresh lines of inquiry into fundamental issues in psychology, artificial intelligence, and evolutionary theory as well as traditional issues in the philosophy of mind.Daniel C. Dennett is Distinguished Arts and Sciences Professor at Tufts University and the author of "Brainstorms" and "Elbow Room." "The Intentional Stance," along with these works, is a Bradford Book.

The Intentional Stance

It has been argued that females should be able to choose parasite-resistant mates on the basis of the quality of male secondary sexual characters and that such signals must be costly handicaps in order to evolve. To a large extent, handicap hypotheses have relied on energetic explanations for these costs. Here, we have presented a phenomenological model, operating on an intraspecific level, which views the cost of secondary sexual development from an endocrinological perspective. The primary androgenic hormone, testosterone, has a dualistic effect; it stimulates development of characteristics used in sexual selection while reducing immu- nocompetence. This "double-edged sword" creates a physiological trade-off that influences and is influenced by parasite burden. We propose a negative-feedback loop between signal intensity and parasite burden by suggesting that testosterone-dependent signal intensity is a plastic re- sponse. This response is modified in accordance with the competing demands of the potential costs of parasite infection versus that of increased reproductive success afforded by exaggerated signals. We clarify how this trade-off is intimately involved in the evolution of secondary sexual characteristics and how it may explain some of the equivocal empirical results that have surfaced in attempts to quantify parasite's effect on sexual selection.

Parasites, bright males, and the immunocompetence handicap

A DNA test to sex most birds.

A combination of field and laboratory investigations has revealed that the temporal patterns of testosterone (T) levels in blood can vary markedly among populations and individuals, and even within individuals from one year to the next. Although T is known to regulate reproductive behavior (both sexual and aggressive) and thus could be expected to correlate with mating systems, it is clear that the absolute levels of T in blood are not always indicative of reproductive state. Rather, the pattern and amplitude of change in T levels are far more useful in making predictions about the hormonal basis of mating systems and breeding strategies. In these contexts we present a model that compares the amplitude of change in T level with the degree of parental care shown by individual males. On the basis of data collected from male birds breeding in natural or captive conditions, polygynous males appear less responsive to social environmental cues than are monogamous males. This model indicates that there may be wi...

The "Challenge Hypothesis": Theoretical Implications for Patterns of Testosterone Secretion, Mating Systems, and Breeding Strategies

Phenotypic plasticity is the ability of a single genotype to produce more than one alternative form of morphology, physiological state, and/or behavior in response to environmental conditions. "Plasticity" and "development" are related terms that are becoming increasingly common in evolutionary biology and ecology. Both phenomena have passed through a period of neglect. In the 1960s Wigglesworth (228, p. 107) described some geneticists as being "apologetic" about environmentally cued polymorphisms, which they considered examples of unfortunate defects in the delicate genetic apparatus: "As R. A. Fisher once said to me, it is not surprising that such elaborate machinery should sometimes go wrong." And Bradshaw (19, p. 148) noted that botanists were carefully avoiding any mention of plasticity; environmental effects in experiments were considered "only an embarrassment." Until recently, genetic considerations have predominated in discussions of evolution and selection. Compared to the enormous progress made in genetics, there has been relatively little systematic effort to analyze environmental effects on the phenotype, and their evolutionary consequences. The plastic phenotype, stigmatized by poorly understood environmental influences and the ghost of Lamarck, has sometimes been lost from view as the focus of selection (e.g. 46; but see 48, 49). Much recent progress has been made toward integrating developmental and evolutionary biology, especially in vertebrate morphology (2, 12, 16, 216), developmental genetics (16, 163, 164), and molecular biology (103; also see 10, 111). "Developmental constraints" is a term symptomatic of this progress, though an unfortunate one because it seems to imply that the main effect of

Phenotypic Plasticity and the Origins of Diversity

The familiar spring sound of birdsongs heralds the onset of territory formation and a complex sequence of interrelated events that make up the breeding period. Such songs are an integral part of the repertoire of aggressive behaviors that males use to advertise and defend territorial boundaries and to attract mates (Fig. 1). It is well established that hormones, particularly testosterone, have stimulatory effects on aggression in reproductive contexts. The prevailing "challenge" hy pothesis asserts that testosterone and aggression corre late only during periods of heightened interactions be tween males. Under more stable social conditions, according to the hypothesis, relation ships among males are maintained by other factors such as social inertia, individual recognition of status, and territorial boundaries, and testoster one levels remain low. Recent re search has suggested ways in which the hypothesis should be modified or extended. In this article we will con_ sider the complexities of aggressive behaviors and their regulation, focusing specifically on species differences in territorial behavior of male birds as models for the multiple interactions of hormones, envi ronment, and behavior. The secretion of testosterone by interstitial cells in the testis is controlled primarily by a glycoprotein, luteinizing hormone, secreted from the anterior pituitary gland (Fig. 2). Testosterone stimulates the development of secondary sex characteristics such as wattles, combs, spurs, the cloacal protuberance (a copulatory organ), and

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Testosterone and Aggression in Birds

Phenotypic plasticity is the extent to which an organism can change its physiology, behaviour, morphology and/or development in response to environmental cues. Environmentally induced differences in the endocrine system are among the underlying causes of phenotypic plasticity. For example, maternal and other environmental influences on developing young can affect the range of physiological and behavioural responses available to them as adults. The mechanisms underlying phenotypic plasticity can be elucidated using multidisciplinary approaches, in which the dynamic interactions among developmental, hormonal and environmental factors are considered. Such studies point to the importance of considering the overall developmental trajectory of an organism when assessing the adaptive value of phenotypic variation, rather than simply evaluating the individual at a single point in time.

Hormones, developmental plasticity and adaptation

Male birdsong is generally regarded as a secondary sexual characteristic under the control of gonadal steroids1,2. Song typically waxes and wanes with the seasonal cycle of testicular growth and regression and decreases after adult castration. Testosterone therapy reinstates song, induces it in females, augments it in intact males, and spring testosterone profiles correlate with seasonal song production3–10. Thus, testosterone has been viewed as a major factor in song acquisition and production3,11–14 acting either directly, or after aromatization within the brain15–16. We show here, however, that song learning and early phases of the development of singing both take place in castrated male birds with no significant levels of testosterone in their blood plasma. Testosterone seems to be required for song crystallization, however. Oestradiol was unexpectedly still present after castration, evidently from a non-testicular source, throughout the period of male song acquisition.

Alfred M. Dufty

Papers

The "Challenge Hypothesis": Theoretical Implications for Patterns of Testosterone Secretion, Mating Systems, and Breeding Strategies

Testosterone and Aggression in Birds

Hormones, developmental plasticity and adaptation

The role of sex steroids in the acquisition and production of birdsong

Vocal communication in the domestic chicken: I. Does a sender communicate information about the quality of a food referent to a receiver?