FEAR AND FEARFULNESS IN ANIMALS

Persistence of individual differences in animal behavior in reactions to various environmental challenges could reflect basic divergences in temperament, which might be used to predict details of adaptive respo nse. Although studies have been carried out on fear and anxiety in var ious species, including laboratory, domestic and wild animals, no cons istent definition of fearfulness as a basic trait of temperament has e merged. After a classification of the events that may produce a state of fear, this article describes the great variability in behavior and in physiological patterns generally associated with emotional reactivi ty. The difficulties of proposing fearfulness - the general capacity t o react to a variety of potentially threatening situations - as a vali d basic internal variable are then discussed. Although there are many studies showing covariation among the psychobiological responses to di fferent environmental challenges, other studies find no such correlati ons and raise doubts about the interpretation of fearfulness as a basi c personality trait. After a critical assessment of methodologies used in fear and anxiety studies, it is suggested that discrepancies among results are mainly due to the modulation of emotional responses in an imals, which depend on numerous genetic and epigenetic factors. It is difficult to compare results obtained by different methods from animal s reared under various conditions and with different genetic origins. The concept of fearfulness as an inner trait is best supported by two kinds of investigations. First, an experimental approach combining eth ology and experimental psychology produces undeniable indicators of em otional reactivity. Second, genetic lines selected for psychobiologica l traits prove useful in establishing relationships between behavioral and neuroendocrine aspects of emotional reactivity. It is suggested t hat fearfulness could be considered a basic feature of the temperament of each individual, one that predisposes it to respond similarly to a variety of potentially alarming challenges, but is nevertheless conti nually modulated during development by the interaction of genetic trai ts of reactivity with environmental factors, particularly in the juven ile period. Such interaction may explain much of the interindividual v ariability observed in adaptive responses.