February 3, 1898] 



NATURE 



327 



Instinct appears to furnish a ground-plan of procedure which 

 is shaped by intelligence to the needs of individual life. And it 

 is often hard to distinguish the original instinctive plan from the 

 subsequent intelligent modification. 



It is not my purpose to describe here in detail, as I have done 

 elsewhere, the results of these observations. It will suffice to 

 indicate some of the more salient facts. In the matter of feeding, 

 the callow young of such birds as the jackdaw, jay, or thrush, 

 instinctively open wide their beaks for the food to be thrust into 

 their mouths. Before the eyes have opened the external stimulus 

 to the act of gaping would seem to be either a sound or the 

 shaking of the nest when the parent bird perches upon it. Under 

 experimental conditions, in the absence of parents, almost any 

 sound, such as a low whistle, lip-sound, or click of the tongue, 

 will set the hungry nestlings agape, as will also any shaking or 

 tapping of the box which forms their artificial nest. And no 

 matter what is placed in the mouth the reflex acts of swallowing 

 are initiated. But even in these remarkably organic responses 

 the influence of experience soon makes itself felt. For if the 

 material given is wrong in kind or distasteful, the eff'ect is that 

 the bird ceases to gape as before to the stimulus. Nor does it 

 continue to open the beak when appropriate food has been given 

 to the point of satisfaction. These facts show that the instinctive 

 act is prompted by an impulse of internal origin, hunger, supple- 

 mented by a stimulus of external origin, at first auditory but 

 later on, when the eyes are opened, visual. They show also that 

 when the internal promptings of hunger cease, owing to satis- 

 faction, the sensory stimulus by itself is no longer operative. 

 And they show, too, that the diverse acts of gaping and swallow- 

 ing become so far connected, that the experience of distasteful 

 morsels tends, for a while at least, to prevent further gaping to 

 the usual stimulus. 



With those birds which are active and alert soon after hatch- 

 ing, the instinctive acts concerned in feeding are of a different 

 character. At first, indeed, the chick does not peck at grains 

 which are placed before it ; and this is probably due to the fact 

 that the promptings of hunger do not yet make themselves felt, 

 there being still a considerable supply of unabsorbed yolk. 

 Soon, however, the little bird pecks with much, but not quite 

 perfect, accuracy at small near objects. But here again experi- 

 ence rapidly plays its part. For if distasteful objects, such as 

 bits of orange-peel, are the first materials given, pecking at them 

 soon ceases ; and if this be repeated, the little bird cannot again 

 be induced to peck, and may even die of starvation. This makes 

 it very difficult to rear by hand some birds, such as plovers, 

 whose natural food, in due variety, is not readily obtainable. It 

 must be remembered, too, that under natural conditions the 

 parent bird calls the young and indicates with her beak the 

 appropriate food ; and this appears to afford an additional 

 stimulus to the act of pecking. Pheasants and partridges seem 

 to be more dependent on this parental guidance than domestic 

 chicks, and they are more easily reared when they have some- 

 what older birds as models whose pecking they may imitate. 

 Passing allusion may here be made to a type of instinctive 

 response in some respects intermediate between the upward 

 gaping of the jay and the downward pecking of the chick. It 

 is seen in the young moorhen, which pecks upwards at food held 

 above it and cannot at first be induced to take any notice of food 

 on the ground. Under natural conditions it is fed by the parent, 

 which holds the food above the little bird as it floats on the 

 water. 



We have then, in these simple instinctive acts, examples of 

 behaviour which is congenitally definite in type for each par- 

 ticular species ; of actions which are the joint product of an 

 internal factor, hunger, and an external factor, sensory im- 

 pressions ; of complex modes of procedure which subserve 

 certain vital needs of the organism. It should be mentioned, 

 however, that the relative definiteness of instinctive responses 

 has been subjected to criticism from a psychological source. It 

 has been urged that the nutritive instincts, the play instincts, the 

 parental instincts, those of self-preservation and those concerned 

 in reproduction, are so varied and multifarious, that definiteness 

 is the last thing that can be predicated of them. Varied and 

 multifarious they are indeed ; and each of the groups above 

 mentioned contains many differing examples. But that is 

 because we are dealing with comprehensive classes of instinctive 

 behaviour. The fact that the group of fishes includes organisms 

 of such wide structural diversity, as the salmon, the globe-fish, 

 the eel, and the sole, does not affect the fact that these species 

 have a relati%'ely definite structure each after his kind. It is 



only when we treat a group of fishes as if it were an individual 

 fish that we are troubled by indefiniteness of structure. And it is 

 only when we deal with a group of instincts, comprised under a 

 class-name, as if it were a particular instinctive act, that we 

 fail to find that definiteness which, to the naturalist, is so 

 remarkable. 



From the physiological point of view, instinctive procedure 

 would seem to have its origin in an orderly group of outgoing 

 neural discharges from the central office of the nervous system 

 giving rise to a definite set of muscular contractions. And this 

 appears to have an organic basis in a congenital preformation in 

 the nervous centres, the activity of which is called into play by 

 incoming messages, both from internal organs in a state of 

 physiological need, and from the external world through the 

 organs of special sense. The naturalist fixes his attention chiefly 

 on the visible behaviour which is for him the essential feature of 

 the instinctive act. But in view of the requirements of psycho- 

 logical interpretation it is advisable to comprise under the term 

 instinct, in any particular manifestation of its existence, the net 

 result of four things : first, internal messages giving rise to the 

 impulse ; secondly, the external stimuli which co-operate with 

 the impulse to affect the nervous centres ; thirdly, the active 

 response due to the coordinated outgoing discharges ; and 

 fourthly, the message from the organs concerned in the be- 

 haviour by which the central nervous system is further affected. 

 Now I shall here assume, without pausing to adduce the argu- 

 ments in favour of this view, that consciousness is stirred in ttie 

 brain, only by incoming messages. If this be so, the outgoing 

 discharges which produce the behaviour are themselves uncon- 

 scious. Their function is to call forth adaptive movements ; and 

 these movements give rise to messages which, so to speak, afford 

 to consciousness information that the instinctive act is in pro- 

 gress. Hence I have urged that the instinctive performance is 

 an organic and unconscious matter of the purely physiological 

 order, though its effects are quickly communicated to conscious- 

 ness in the form of definite messages from the motpr organs. ' I 

 have not denied that the stimuli of sight, touch, hearing and so 

 forth, also have conscious effects ; I do not deny (though here I 

 may have spoken too guardedly) that the initiating impulse of in- 

 ternal origin, is conscious. In both these cases we have messages 

 transmitted to the central office of the brain. What I have 

 ventured to urge is that the consciousness of instinctive be- 

 haviour, in its completed form, does not arise until further 

 messages come in from the motor organs implicated in the per- 

 formance of the act, lodging information at the central office 

 concerning the nature of the movements. 



A diagram will perhaps serve to make this conception clearer. 



Impulse 



Stimulus 



Instinctive behaviour. 



The circle represents the brain, in some part of which con- 

 sciousness arises through the effects of incoming nerve-currents. 

 Under the influence of the two primary groups of messages, due 

 to impulse and to sensory stimulus, consciousness is evoked, and 

 the brain is thrown into a state of neural strain, which is re- 

 lieved by the outgoing discharge to the organs concerned in the 

 instinctive behaviour. It is this outgoing discharge which I 

 regard as unconscious. But the actions which are thus pro- 

 duced give rise to a secondary group of incoming messages from 

 the moving limbs. This it is which gives origin to the con- 

 sciousness of instinctive behaviour as such. And I regard it as 

 psychologically important that these incoming messages are 

 already grouped, so as to afford to consciousness information, 

 rather of the net results of movement than of their subsidiary 

 details. 



So much for our general scheme. If now we turn to the 

 instinctive behaviour concerned in locomotion, we find a con- 

 genital basis upon which the perfected activities are founded. 

 There is no elaborate process of learning to walk on the part of 

 the chick ; ducklings and moorhens a few hours old swim with 

 perfect ease when they are placed in water ; these birds also 

 dive without previous practice or preliminary abortive attempts ; 

 while young swallows, if their wings are sufficiently large and 

 strong, are capable of short and guided flights the first time they 

 are committed to the air. In these cases neither the internal 

 impulse, nor the sensory stimuli, are so well defined as in the 

 case of the nutritive activities. The impulse probably takes the 



NO. 1475, VOL. 57] 



