fresh air; a large rise or fall in temperature elicits attempts to find a more equable ambient temperature; an environment lacking water of food elicits attempts to find a more congenial habitat. Insofar as it is again behavioural systems that are under load the condition is likely to be references to as one of psychological and emotional stress.
The position regarding disturbances of morphological and physiological homeostasis is a little more complicated because, in the regulation of steady states of those sorts, two types of regulatory systems are called upon, physiological as well as behavioural. The term ‘physiological stress’, it should be noted, however, is habitually used to refer only to the load placed upon the relevant physiological systems. Insofar as a load may also be placed on relevant behavioural systems, the condition is referred to as one not of physiological but of psychological (or emotional) stress. An illustration is as follows: a person is suffering from incipient heat stroke in a desert. Physiological systems to reduce temperature are active and under heavy load. His condition would, further, be referred to as one of physiological stress. Yet simultaneously he might be struggling to escape the sun by climbing to a cave half‐way up a cliff, but be finding the feat almost beyond him. His mental state might then be referenced to as one of psychological (or emotional) stress.
The position regarding disturbances of representational homeostasis is also a little complicated because, here again, two types of regulatory systems are called upon: psychological systems as well as behavioural ones. Current usage, it appears, is to refer to the condition as one of psychological (or emotional) stress when there is any disturbance of homeostasis, irrespective of which type of regulatory systems is relied upon. Let us consider the two types of systems successively.
Representational homeostasis, it is postulated, is maintained and restored in large part by the activation of perceptual‐cognitive processes that filter and interpret sense data in ways that maintain current working models intact. Whenever the validity of a working model is called in question by the reception of incompatible yet mighty information, there is disturbance of representational homeostasis; and the perceptual‐cognitive processes activated are consequently under load. An example is a person whose basic beliefs and assumptions about the world, whether framed in religious, political or scientific form, are called seriously in question by someone whom the person regards with respect. One the one hand, the person wishes to retain his original beliefs; on the other, he finds it difficult to ignore the contrary opinion. It is clearly in accordance with current usage to refer to condition as being one of psychological stress.
An alternative way of maintaining representational homeostasis is, by appropriate behaviour, to select the information likely to reach us so that it accords with our present working models. Whatever we suspect of being incompatible is almost automatically avoided, and a substantial effort may have to be made to give it attention. Much of this selection is achieved behaviourally by selecting what we read and listen to, though, as already indicated, much censoring is done also after our sense‐organs have been exposed to the unwanted information. Should a person be forced against his wish to listen to incompatible views, as in a brain‐washing session, the experience would clearly be regarded as stressful; and his condition would be described as one of psychological (or emotional) stress.
To sum up, the terms ‘physiological stress’ and ‘psychological (or emotional) stress’ are used today respectively to refer, not to a disturbance of any particular category of homeostasis, but to the type of regulatory system that is called upon to restore the disturbance. Whenever physiological systems are activated the organism is (or may be) described as undergoing physiological stress; whenever either behavioural or psychological systems are activated the organism is (or may be) described as undergoing psychological (or emotional) stress.
Thus far, the discussion has considered only actual disturbances of one or another category of homeostasis. In examining problems of psychological stress and anxiety, however, it is situations of threatened disturbance that are often of special importance.
Threats of Disturbance of Homeostasis
A stressor has been defined as any change in the internal state or external environment that disturbs a steady state and thereby elicits regulatory processes that have as their predictable outcome restoration of whatever steady state has been disturbed. Living organisms, however, usually do not wait for a stressor to act. More often than not they are forewarned and take one or another type of action the consequences of which are either to avoid the stressor’s striking or else to mitigate or cancel its effects.
It is evident that, in the development of an animal’s capacity to take appropriate avoiding action, learning plays a major role. Every experiment in which an animal suffers punishment if it fails (e.g. when the buzzer goes it must press the right bar, or must turns down the right branch of a maze) is concerned with such learning. Nevertheless, there is good evidence that, in addition to all the cues portending trouble that are learned, there are other sorts of cues that lead animals to withdraw but that do not have to be learned. The strong tendency to avoid anything strange, which appears to be universal in birds and mammals, is one of the best investigated examples. The response of birds to the alarm call of their own species, and often to those of relative species, is another.
That many of the cues that elicit avoiding action should be responded to instinctively is hardly surprising. For if every individual had to learn for itself the hard way what was dangerous and what safe casualty rates would be enormous. To respond to everything strange with caution or escape may perhaps lead on many occasions to unnecessary timidity; but if on even only a few occasions it saves life it is intuitively worthwhile. Better to be safe than sorry.
The obverse of avoiding the strange is to remain close to the familiar. Remaining close to the familiar is, of course, the state of affairs maintained in personal‐environmental homeostasis; and a principal position of this essay is that maintenance of personal environmental homeostasis is a particularly efficient method of forestalling and avoiding disturbances to morphological and physiological homeostasis, and also to ecological homeostasis. A corollary of that proposition is that the reason that, during evolution, higher vertebrates have become equipped with environmentally stable behavioural systems that have the effect of keeping an animal within its own familiar environment and close to its own familiar companions is that such systems, by maintaining that animal within a relatively safe arena, all make a major contribution to species survival.
The persistence of traditional customs in social groups, not only of man but also of some sub‐human primates (e.g. food habits of chimpanzees) and of some birds (e.g. migrating habits of geese), can be looked at in the same light. Although obviously the details of such customs are learned, there seems to be a strong tendency in the young to adopt the customs of the group in which they are [illeg.] and a strong tendency in other members to enforce conformity.
The same seems to obtain for a working model of the world. Each social group has its own such model which is acquired by the young during the course of their education. Despite the existence of well‐known exceptions in economically advanced countries, it seems likely that these conformist tendencies are an expansion of a genetic bias to develop in a conformist way in any environment that is not too far removed from the species environment of evolutionary adaptedness.13
Exploration and innovation are not overlooked. Even in animal societies and in tradition‐rooted human societies such exploration and innovation occur. Where westernised societies are unusual is in the amount of exploration and innovation that they encourage and, especially, in the high valuation nowadays put upon it. But it needs to remembered that such shift in balance between tradition and innovation is not only historically very recent but is giving rise to much unforeseen and unwanted instability. Whilst in the short run the survival value of western innovation is undeniably high, its survival value in the long run remains unproven.
It is true that a familiar
