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In: Behaviour
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Abstract

A. A number of very different meanings have been given to the term "arousal". These have here been distinguished as follows: (1a) Responsiveness. The likelihood at a particular moment that any one of a number of different stimuli will evoke the response appropriate to it if presented. (ib) Behavioural intensity. A variable which affects the vigour and completeness of whichever response is elicited. (2) Activation. A variable, systematic changes in which determine the kind of response which is possible (e.g. grooming or copulation). (3) Arousal as drive. A variable which explains the association together in time of a group of responses, which may be held to include alert responses, cardiac acceleration, increase in postural tonus and a variety of "emotional" responses. (4) Level of sensory input. A variable which regulates the level of sensory input. Mechanisms of selective attention are often included. (5) Property of a functional system in the CNS. The syndrome resulting from increased activity in the ascending activating system. Some or all of these meanings are commonly confused together, which greatly reduces their value in description and analysis. Further it is usually assumed, but with little little firm evidence, that changes in all these variables are continuous and similar in nature from deep sleep to states of extreme wakefulness. These latter states have rarely been clearly characterised. B. For a number of studies the use made of arousal as an explanatory concept is discussed. (1) Changes in responsiveness are important in behaviour, and deserve wider study and theoretical discussion. Data on behavioural intensity are scanty. (2a) Activation models can be used to explain changes in the likelihood of different acts through the course of normal behavioural cycles from one period of sleep to the next. However, except for grooming which tends to occur before and after drowsiness, most acts appear to be affected by a general progressive increase in responsiveness following awakening. The existence of a number of groups of acts, each associated with a particular range of activation (arousal) remains to be proved. (2b) Experimental manipulation of drowsiness in the chick by the administration of hexoses either into the crop or directly into the hypothalamus and other areas of the brain, has at least three relatively independent effects on behaviour. Drowsy periods interfere directly with other responses. At the same time approach to drowsiness is accompanied by a loss of inhibition in responses such as pecking. This is probably due to reduced forebrain activity since it can be reproduced by spreading depression due to KCl. Finally, familiar surroundings are treated as novel immediately after waking. The second and third effects cannot be handled by activation models. (2c) Attempts to vary activation by startling and painful stimuli have shown that some responses may be markedly and unexpectedly facilitated (e.g. copulation by electric shock). However, other startling stimuli may have no effect at all, and recovery from the stimulus does not show the sequential facilitation of a number of different acts which an activation model would predict. (3) Various cardiovascular, respiratory, thermoregulatory and other reflexes, which represent feedforward regulation of the physiological consequences of a predicted increase in exertion, have been held to be indices of heightened arousal. Their use as such is complicated by the fact that the sustained activation of such reflexes in the absence of exertion is inevitably disturbed by feedback regulation of the disturbances which result. Further, a novel stimulus can also produce preparations for immobility (e.g. cardiac deceleration), if the animal examines it carefully rather than at once responding. Attempts to explain changes in these two complexes of reflexes in terms of arousal changes have become so confusing that they are best abandoned. The pattern of alert responses shown at waking is commonly taken as the behavioural counterpart of cortical arousal. However, once waking has occurred it is not possible to identify further patterns of alert responses which can be used to characterise a series of states of progressively increasing arousal. Instead at least two phases of attention, scanning and focussed, can be distinguished over a wide range of states of responsiveness or autonomic arousal. (4) Estimates of the rate of intake or of passage of information are extremely difficult. They are complicated by the fact that studies of selective attention have shown that preliminary recognition of stimuli proceeds in channels other than that in primary use, so that any definition of arousal in terms of information passage must also consider the extent to which attention is confined to the primary channel. Evidence for the homeostatic regulation of arousal, so defined, is indirect and scanty. (5) At least two brain mechanisms are primarily responsible for different phenomena which have been ascribed to arousal. The ascending activating system (AAS) is involved in the appearance of alert responses in a previously drowsy animal, whilst the central mesencephalic grey (CMG) and its diencephalic connections appear to mediate both preparations for exertion and such "emotional" responses as piloerection. The relationship between the two systems and, in particular, the effects of sustained activation of the AAS in the absence of effects on the CMG require further study uncomplicated by prior assumptions about the nature of arousal. It is probable that other of the phenomena discussed here are also primarily mediated by relatively independent brain structures (e.g. focussed attention and the hippocampus).

In: Behaviour
Author:

Abstract

1. The change from the low intensity mobbing call 'duck' to the high intensity call 'tix' involves the addition of what is probably the first overtone and a slight rise in pitch of the fundamental tone. The first change has a lower threshold than the second. 2. Bouts of calls are usually associated with flights and commonly begin a little before take-off. 3. At or near take-off there is a change (the 'flight effect') which tends to initiate calling if it has not begun, and to accelerate it and/or cause the change from 'duck' to 'tix', if it has. 4. Experimental prolongation of flight prolongs calling and promotes the change to a 'tix' type of call. 5. Bouts of calls given when perched are accompanied by activity of the system controlling flight, which does not reach the threshold for take-off.

In: Behaviour
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Abstract

I. The factors causing A to rise tend to increase for at least 60 sec. after the appearance of the owl (although there is some effect on calling in a second or less), and the values of T tend to increase for at least 15-30 sec. 2. The changes following the disappearance of the owl are similar to those occurnng in waning (disappearance of bouts given when perched, and calls before take-off ; lengthening of intervals between calls) but occur much more quickly (e.g. within 5 sec.). It is unnecessary therefore to postulate a progressive change in the system directly controlling calling in order to explain waning (although this cannot be excluded) ; the change could be solely in the perceptual organisation responsible for recognition of the owl. 3. Differences between calling in flight towards and away from the owl depend solely on differences in distance from the owl at take-off. There is no evidence that flights away from the owl are caused by an increase in the frightening effect of the owl; at least, calling shows no effect due to such an increase. Flight, like calling, is probably directly controlled by a system which is affected by a number of factors besides the sight of the owl.

In: Behaviour
Author:

Abstract

1. At least two variables must be used for the adequate analysis of the changes observed in calling. The first has been here termed Action Potential (A). When the value of A at calling is above a certain threshold 'tix' is given instead of 'duck'. A is caused to rise both by activity of the neural system controlling flight and by the sight of a frightening object. It is reduced by calling, probably at or just after each call. 2. A second variable, the General Threshold for calling (T), must also be employed to explain the data obtained. When A is below T no calls can occur. T is increased by calling (probably at each call, since there is some evidence that it decays between calls). It therefore rises progressively during bouts. As a result the interval between the last two calls of a bout is an unusually long one, and the change to 'tix' is irreversible within a bout. Between bouts T decays, so that the longer the pause between bouts the shorter the intervals between calls at the beginning of the next bout, and the less likely is it that the first call will be 'tix'. 3. The higher the value of T at the beginning of a bout the longer the intervals between calls and the more likely is the change to 'tix', since A has to rise to equal T before calling can occur. 4. T tends to fall a take-off and rise at landing. 5. High intensity calling may take two forms which are caused by differences in the rate of accumulation of T. When T accumulates slowly the intervals between calls readily decrease until the physical limit is reached, and a scream results, in the course of which the change to a 'tix' type of calling occurs. A scream is initiated only after the activity of flight has continued for more than a minimum period of time, which is longer the lower the intensity of mobbing. When T accumulates readily, long bouts result, which are entirely composed of 'tix' calls, given at unusually long intervals.

In: Behaviour
Author:

Abstract

I. All the main vocalisations of the Blackbird (excluding song) have as one of their causes the presence of a frightening object. The alarm call 'seee' may depend on the same action potential as the 'duck' group of calls. The causation of mobbing calls given in subsong is discussed. 2. The motivational organisation underlying the mobbing calls is such that they (or their variants) occur adaptively in a number of quite different contexts (e.,g. mobbing, fledgling location calls) and also in a context (reproductive fighting) where they are probably not adaptive. 3. Two Buntings (Emberiza spp.) have calls which are apparently motivated in the same way as the 'duck' group of calls. In one of them, the general threshold for calling appears to be permanently high in the adult. 4. The motivation of behaviour by a 'conflict of drives' is discussed. A simple behaviour pattern which genuinely depends on the interaction of two systems controlling groups of acts may be caused in two different ways. It may depend on the summation of positive effects from both systems. Alternatively it may depend on only one of the systems, but occur only when other systems are competing with it for control of effectors, so that the action potential for the behaviour pattern rises unusually high. The theoretical consequences of such competition (which can be represented by a variable of the general threshold type) are discussed; they appear not to have been fully recognised previously. Evidence is given that such interactions affect behaviour other than vocalisations.

In: Behaviour
In: Behaviour
In: Behaviour
In: Again, Dangerous Visions: Essays in Cultural Materialism
In: Again, Dangerous Visions: Essays in Cultural Materialism