St Thomas Aquinas wrote that animal judgement is not free but implanted by nature. Thus, from an early time, instinctive behaviour was regarded as the counterpart to voluntary behaviour. In everyday, though not in scientific, speech the term 'instinct' is still used to imply 'without thought'. For example, if I heard a taxi driver say, 'I instinctively stamped on the brakes', I would assume that he meant that his behaviour was
reflex or involuntary, and not that he was born with an innate ability to apply the brakes in motor cars.
The associationists believed that human behaviour is maintained by the knowledge of, and desire for, particular consequences of behaviour, and they looked upon notions of instinct with disfavour. However,
John Locke did concede that there was 'an uneasiness of the mind for want of some absent good. ... God has put into man the uneasiness of hunger and thirst, and other natural desires ... to move and determine their wills for the preservation of themselves and the continuation of the species' (
An Essay Concerning Human Understanding, 1690). Francis Hutcheson argued that instinct produces action prior to any thought of the consequences (
An Essay on the Nature and Conduct of Passions and Affections, 1728). Thus Hutcheson made instinct into a kind of motivational force, and this concept was taken up by the 19th-century rationalists, such as
William James, who conceived of human nature as a combination of blind instinct and rational thought.
The irrational forces in man's nature were emphasized by
Freud, but the ideas of William
McDougall (1871–1938) probably had a greater influence upon the scientific development of the concept of instinct. McDougall regarded instincts as irrational and compelling motivational forces. He enumerated particular instincts, each of which was accompanied by an
emotion. Examples are: pugnacity and the emotion of anger; flight and the emotion of fear; repulsion and the emotion of disgust (
Instincts and their Vicissitudes: Collected Papers, 1915). McDougall's views do not find favour with modern psychologists because they are derived from subjective experience and are therefore hard to verify. There is inevitable disagreement among psychologists as to the number of instincts that should be allowed.
A different line of thought was initiated by
Charles Darwin. In his
Origin of Species (1859), Darwin treated instincts as complex reflexes that were made up of inherited units and therefore subject to natural selection. Such instincts would evolve together with other aspects of the animal's morphology and behaviour. Darwin laid the foundations of the classical ethological view propounded by Konrad Lorenz and Niko Tinbergen. See
ethology.
Lorenz maintained that animal behaviour included a number of fixed-action patterns that were characteristic of species and largely genetically determined. He subsequently postulated that each fixed-action pattern or instinct was motivated by action-specific energy. The action-specific energy was likened to liquid in a reservoir. Each instinct corresponded to a separate reservoir, and when an appropriate releasing stimulus was presented the liquid was discharged in the form of an instinctive drive which gave rise to the appropriate behaviour. Tinbergen proposed that the reservoirs, or instinct centres, were arranged in a hierarchy so that the energy responsible for one class of activity, such as reproduction, would drive a number of subordinate activities, such as nest building, courting, and parental care.
The concept of instinct that is identified with classical ethology does not find favour with the majority of present-day behavioural scientists, for two main reasons. The first reason is connected with the idea that there are instinctive forces, or drives, that determine certain aspects of behaviour. Although the notion of drive as an energizer has been very influential in psychology, it involves a misuse of the concept of energy. In the physical sciences, energy is not a causal agent but a descriptive term arising from mathematically formulated laws. Analogous laws can be formulated for animal behaviour, but they do not lead to a concept of energy that corresponds to the notions of drive popular with the early psychologists and ethologists. Although the idea of drive as an energizer of behaviour has intuitive appeal, this is not nowadays regarded as sufficient justification for a scientific concept. In addition there are empirical problems. Early psychologists sought to identify a drive for every aspect of behaviour: a hunger drive responsible for feeding, a thirst drive, a sex drive, etc. It proved impossible to classify animal behaviour in this way without resorting to a
reductio ad absurdum involving drives for thumb sucking, nail biting, and other minutiae of behaviour. A more modern view is that animals choose from among the set of alternative courses of action that is available at a particular time, in accordance with certain precisely formulated principles of decision making. This approach obviates the view that animals are driven by instinctive forces to perform particular behaviour patterns.
The second reason for abandoning the classical concepts of instinct is an objection to the implication that certain aspects of behaviour are innate in the sense that they develop independently of environmental influences. Most scientists now recognize that all behaviour is influenced both by the animal's genetic make-up and by the environmental conditions that exist during development. The extent to which the influences of nature and nurture determine behaviour varies greatly from activity to activity and from species to species. For example, the vocalizations of pigeons and doves are relatively stereotyped and characteristic of each species, and are not influenced by auditory experience after hatching. The vocalizations of other birds, however, may depend heavily upon such experience, as in the strongly imitative birds, or they may be partly influenced by experience. For example, chaffinches will learn the song they hear during a particular sensitive period of early life, provided it is similar to the normal song.
While the influence of particular genes may be necessary for the development of a behaviour pattern, it is never a sufficient condition. All types of behaviour require a suitable embryonic environment for the correct nervous connections etc. to develop. Normally, the physiological medium provided by the parent is designed to ensure that normal embryonic development occurs. Just as the parent provides an environment suitable for the development of the embryo, so it may provide an environment suitable for the development of a juvenile. Thus a chaffinch is normally reared in an environment in which it inevitably hears the song of other chaffinches, and so it develops the song that is characteristic of its own species.
Even apparently stereotyped activities may, upon closer examination, be shown to be influenced by the environment. For example, the newly hatched chicks of herring gulls peck at the tip of the parent's bill, which bears a characteristic red spot on a yellow background. The chick's behaviour induces the parent to regurgitate food. The behaviour is typical of all newly hatched chicks, is performed in an apparently stereotyped manner, and would appear to be a classic example of instinctive behaviour. Upon closer examination, however, it can be seen that the initial behaviour of individual chicks varies considerably in force and rapidity of pecking, angle of approach, and accuracy. As the chicks gain experience their pecking accuracy improves, and the pecking movements become more stereotyped. Some of these changes are due to maturation. The chicks become more stable on their feet as their muscles develop, and their pecking coordination improves. Some of the changes are due to learning. Initially the chicks peck at any elongated object of a suitable size. Although the red spot on the parent's bill is attractive to them, it is not their only target. Once the chicks begin to receive food they learn to exercise greater discrimination. It is not surprising that the behaviour of different chicks develops along similar lines, because in the natural environment they are all confronted with a similar situation. Practice and experience in similar situations lead to similar results, and the behaviour of the older chick consequently becomes more and more like that of its peers.
The concept of instinct has undergone many changes over the years. Whereas, at one time, instinctive behaviour was seen as inborn, stereotyped, and driven from within, the modern approach is to treat the innate, the reflex, and the motivational aspects as separate issues. While much animal and human behaviour is innate in the sense that it inevitably appears as part of the repertoire under natural conditions, this does not mean that genetic factors are solely responsible. Modes of learning that are characteristic of the species may be just as important. Much of the nature–nurture controversy, particularly that associated with sexual and racial differences among humans, results from a failure to recognize the vast complexity of developmental processes.
(Published 1987)— D. J. McFarland
Bibliography- Hinde, R. A., Hinde, J. S., and Head, J. J. (1987). Instinct and Intelligence.
