Page:The New International Encyclopædia 1st ed. v. 02.djvu/258

ATTENTION. of the real world. What has happened, that is of psychologieal moment, during this experience?

In the first place, the general state or condition of my whole consciousness has changed. In the older psychologies the jihrase 'state of consciousness' is used as the equivalent of what is now termed, more correctly, 'mental process': ideas and emotions and desires were referred to as "states of consciousness.' What is here meant is something very difTerent. We speak of the 'state' of consciousness, in strict usage, in the sense in which we speak of the state of the roads, as good or bad; or of the state of a man's affairs, as flourishing or embarrassed; or of the state of his health, as robiist or shat- tered. Now it is clear that the state or disposi- tion of consciousness, in discursive thought or reverie, differs from its state, understood in this way, in concentrated attention. In the former case, all the ideas which constitute the consciousness are on the same level, of the same mental value; in the latter, some ideas (those held at the focus of attention) are superemi- nently "robust' or 'flourishing,' while the ideas not attended to are depressed, relegated to the background. Here, then, is a matter that re- quires accurate analysis. Secondly, there is a marked difl'erence of mental experience, as the distracted, thwarted attention with which we begin the reading of the novel passes into the rapt and absorbed interest with which we con- tinue to read. We are attentive in both eases; but if we are to judge by what we 'feel,' we can hardly give the same name, without qualification, to the two states of consciousness. In other words, there seem to be various forms or kinds of attention. Thirdly, the change of conscious state which comes with the concentration of attention brings with it a characteristic change of bodily attitude. We should all recognize a picture or statue that portrayed the scout (i.e. the attitude of visual attention), or the eaves- dropper (the attitude of auditory attention). These attitudes naturally give rise to certain characteristic groups of organic sensation — of sensations from skin and nniscle. tendon and joint : and we shall therefore e.xpect to find such sensations playing a constant and important part among the sense-processes that form the hack- ground of the attentive consciousness.

We will take up these topics in order, begin- ning ( 1 ) with attention as a state of conscious- ness. What are the essential features of the attentive state? (a) The ideas attended to are more clear and distinct than the ideas simul- taneously present, but neglected b}- the atten- tion, or, as we may say, attended from. The processes at the focus of attention are readily discriminated ; the ideas of the background are obscure, (b) If the ideas attended to are in- trinsically weak, they are strengthened or in- tensified by attention. A faint sound or light is rendered louder or brighter as we attend to it. No such intensification is observable in the case of ideas whose stimuli are intrinsically strong, (c) If the ideas attended to are fleeting and transient, they can be lengthened, made more durable, by attention. No such lengthening is observable in the ease of ideas whose stimuli are stable and permanent. Lastly, (d) the ideas attended to are more valuable for the general mental life than are the ideas attended from; they are more easily and certainly revivable, in memory and imagination. It is a commonplace, of education that if we wish a child to remember something, we must make him attend to it. This, fourth characteristic is, evidently, of a different, order from the three preceding. It is a result, or after-effect of the others, and more especially of (a).

As to the physical basis of these changes in con.sciousness, it has long been known that cer- tain nervous impulses within the central nervous system have the power of inhibiting or arresting other impulses ; thus, excitation of the vagus, (pneumogastrie, or tenth cranial) nerve inhibits- the beating of the heart (Weber). Now we can account for some of our observed phenomena by a theory of inhibition. Vhen e.g. a weak men- tal process is strengthened, or a transient process, lengthened, we may well suppose that the effect is due. not to any positive reinforcement or temporal extension of the process in question, but simply to the simultaneous arrest of other and conflicting excitations w-ithin the nervous system. Attention, that is to say, allows the weak or transient process to come to its full in- tensive and temporal rights in consciousness- by keeping down other nei-^'ous impulses whose tendency is still further to weaken or curtail that process. Attempts have been made, in the same way, to explain the growth of clearness and distinctness in the ideas attended to by assum- ing an inhibition of conflicting ideas ; so that the clearness of the attentive state would repre- sent the normal or natural clearness of the idea, the clearness which it can attain when its de- velopment is not hindered by rival ideas. Physi- ologists, however, have recently discovered that, just as certain nervous impulses may arrest other impulses, or l)lock paths of nervous dis- charge, so may certain impulses reinforce otliei"s, or open up paths of nervous discharge; the negative fact of inhibition is paralleled by the positive fact of facilitation. There seems to be no reason why we should not avail ourselves of this discovery for our theory of attention. The clearness of the idea attended to would then de- pend partly upon the arrest of conflicting ideas, but partly also upon an actual enhancement of the focal idea by the reinforcing nervous im- ]iulses. Such a view accords better with the observed mental phenomena than does the view which regards all the aspects of the attentive state as symptoms of neural inhibition. On the question of the primary seat of the inhibitory and facilitating impulses, no more can at pres- ent be said than tluit it is, probably, to be sought in the 'association centres' of the cerebral cor- tex. (See Nervous System d Br.in.)

Two special questions arise out of the fore-going discussion. We may ask, in the first place, how long the state of attention continues? for how long a time an idea or group of ideas may remain poised at the apex of conscious clearness? And we may ask, secondly, how large the group of ideas attended to may be; inquiring now into the range of attention, as we have before inquired into its duration. Both questions have been submitted to the test of experiment. It has been found, (a) that the state of attention is not continuous, but intermittent. Suppose that we look attentively at a faint gray patch on a white surface, or listen attentively to the faint hiss of a gas-flame. If the attention remains steady, the gray and the hiss will also remain