Front Page Titles (by Subject) CHAPTER III.: THE GROWTH OF INTELLIGENCE. - The Principles of Psychology
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CHAPTER III.: THE GROWTH OF INTELLIGENCE. - Herbert Spencer, The Principles of Psychology 
The Principles of Psychology (London: Longman, Brown, Green and Longmans, 1855).
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THE GROWTH OF INTELLIGENCE.
§ 179. The law enunciated in the foregoing chapter, being the law of Intelligence in the abstract—the law which Intelligence tends more and more completely to fulfil the further it advances, we have next to examine the several modes in which the more complete fulfilment of this law is exhibited; and to inquire whether there is any general cause for an ever-increasing fulfilment of it.
Commencing with some lowly-endowed creature, respecting which it can be scarcely at all said, that the strength of the tendency which the antecedent of any psychical change has to be followed by its consequent, is proportionate to the persistency of the union between the external things they symbolize; we may note three several modes in which the progression shows itself. There is, first—increase in the accuracy with which the inner tendencies are proportioned to the outer persistencies. There is, second—increase in the number of cases, differing as to kind but like as to grade of complexity, in which there are inner tendencies answering to outer persistencies. And there is, third—increase in the complexity of the coherent states of consciousness, answering to coherent complexities in the environment. The organism is placed amidst an infinity of relations of all orders. It begins by imperfectly adjusting its actions to a few of the very simplest of these. To adjust its actions more exactly to these few simplest, is one form of advance. To adjust its actions to more and more of these simplest, is another form of advance. To adjust its actions to successive grades of the more complicated, is yet another form of advance. And to whatever stage it reaches, there are still the same three kinds of progression open to it—a perfecting of the correspondences already achieved; an achievement of other correspondences of the same order; and an achievement of correspondences of a higher order: all of them implying further fulfilment of the law of intelligence.
But now, what are the conditions to these several kinds of progression? Is the genesis of Intelligence explicable on any one general principle applying at once to all these modes of advance? And if so, what is this general principle?
§ 180. As, in the environment, there exist relations of all orders of persistency, from the absolute to the fortuitous; it follows that in an intelligence displaying any high degree of correspondence, there must exist all grades of strength in the connections between states of consciousness. As a high intelligence is only thus possible, it is manifestly a condition of intelligence in general, that the antecedents and consequents of psychical changes shall admit of all degrees of cohesion. And the fundamental question to be determined, is:—How are these various degrees of cohesion adjusted?
Concerning their adjustment, there appear to be but two possible hypotheses, of which all other hypotheses can be but variations. It may on the one hand be asserted, that the strength of the tendency which each particular state of consciousness has to follow any other, is fixed beforehand by a Creator—that there is a pre-established harmony between the inner and outer relations. On the other hand it may be asserted, that the strength of the tendency which each particular state of consciousness has to follow any other, depends upon the frequency with which the two have been connected in experience—that the harmony between the inner and outer relations, arises from the fact, that the outer relations produce the inner relations. Let us briefly examine these two hypotheses.
The first receives an apparent support from the phenomena of reflex action and instinct; as also from those mental phenomena on which are based the doctrine of “forms of thought.” But should these phenomena be otherwise explicable, the hypothesis must be regarded as altogether gratuitous. Of criticisms upon it, the first that may be passed, is, that it has not a single fact to rest upon. These facts that may be cited in its favour, are simply facts which we have not yet found a way to explain; and this alleged explanation of them as due to a pre-established harmony, is simply a disguised mode of shelving them as inexplicable. The theory is much upon a par with that which assigns, as the cause of any unusual phenomenon, “an interposition of Providence;” and the evidence for the one is just as illusive as that for the other. A further criticism is, that even those who lean towards this theory dare not apply it beyond a narrow range of cases. It is only where the connections between psychical states are absolute—as in the so-called forms of thought, and the instinctive actions—that they fall back upon pre-established harmony. But if we assume that the adjustment of inner relations to outer relations, has been in some cases fixed beforehand, we ought in consistency to assume that it has been in all cases fixed beforehand. If, answering to each absolutely persistent connection of phenomena in the environment, there has been provided some absolutely persistent connection between states of consciousness; why, where the outer connection is almost absolutely persistent, and the inner connection proportionately persistent, must we not suppose a special provision here also? why must we not suppose special provisions for all the infinitely varied degrees of persistency? The hypothesis, if adopted at all, should be adopted in full. The consistent adoption of it, however, is declined, for sundry very obvious reasons. It would involve the assertion of a rigorous necessity in all thought and action—an assertion to which those leaning towards this hypothesis, are, more than any others, opposed. It would imply that at birth there is just as great a power of thinking, and of thinking correctly, as at any subsequent period. It would imply that men are equally wise concerning things of which they have had no experience, as concerning things of which they have had experience. It would altogether negative the fact, that those who have had a limited and exceptional experience come to erroneous conclusions. It would altogether negative that advance in enlightenment which characterizes human progression. In short, not only is it entirely without foundation in our positive knowledge of mental phenomena; but it necessitates the rejection of all such positive knowledge of mental phenomena as we have acquired.
While, for the first hypothesis, there is no evidence, for the second the evidence is overwhelming. The multitudinous facts commonly cited to illustrate the doctrine of association of ideas, support it. It is in harmony with the general truth, that from the ignorance of the infant the ascent is by slow steps to the knowledge of the adult. All theories and all methods of education take it for granted—are alike based on the belief that the more frequently states of consciousness are made to follow one another in a certain order, the stronger becomes their tendency to suggest one another in that order. The infinitely various phenomena of habit, are so many illustrations of the same law: and in the common sayings—“Practice makes perfect,” and “Habit is second nature,” we see how long-established and universal is the conviction that such a law exists. We see such a law exemplified in the fact, that men who, from being differently circumstanced, have had different experiences, reach different generalizations; and in the fact that an erroneous connection of ideas will become as firmly established as a correct one, if the external relation to which it answers has been as often repeated. It is in harmony with the familiar truths, that phenomena altogether unrelated in our experience, we have no tendency to think of together; that where a certain phenomenon has within our experience occurred in many relations, we think of it as most likely to recur in the relation in which it has most frequently occurred; that where we have had many agreeing experiences of a certain relation, we come to have a strong belief in that relation; that where a certain relation has been daily experienced throughout our whole lives, with scarcely an exception, it becomes extremely difficult for us to conceive it as otherwise—to break the connection between the states of consciousness representing it; and that where a relation has been perpetually repeated in our experience with absolute uniformity, we are entirely disabled from conceiving the negation of it—it becomes absolutely impossible for us to break the connection between the answering states of consciousness.
The only orders of psychical sequence which do not obviously come within this general law, are those which we class as reflex and instinctive—those which are as well performed on the first occasion as ever afterwards—those which are apparently established antecedent to experience. But there are not wanting facts which indicate that, rightly interpreted, the law covers all these cases too. Though it is manifest that reflex and instinctive sequences are not determined by the experiences of the individual organism manifesting them; yet there still remains the hypothesis that they are determined by the experiences of the race of organisms forming its ancestry, which by infinite repetition in countless successive generations have established these sequences as organic relations: and all the facts that are accessible to us, go to support this hypothesis. Hereditary transmission, displayed alike in all the plants we cultivate, in all the animals we breed, and in the human race, applies not only to physical but to psychical peculiarities. It is not simply that a modified form of constitution produced by new habits of life, is bequeathed to future generations; but it is that the modified nervous tendencies produced by such new habits of life, are also bequeathed: and if the new habits of life become permanent, the tendencies become permanent. This is illustrated in every creature respecting which we have the requisite experience, from man downwards. Though, among the families of a civilized society, the changes of occupation and habit from generation to generation, and the intermarriage of families having different occupations and habits, very greatly confuse the evidence of psychical transmission; yet, it needs but to consider national characters, in which these disturbing causes are averaged, to see distinctly, that mental peculiarities produced by habit become hereditary. We know that there are warlike, peaceful, nomadic, maritime, hunting, commercial races—races that are independent or slavish, active or slothful,—races that display great varieties of disposition; we know that many of these, if not all, have a common origin; and hence there can be no question that these varieties of disposition, which have a more or less evident relation to habits of life, have been gradually induced and established in successive generations, and have become organic. That is to say, the tendencies to certain combinations of psychical changes have become organic. In the domesticated animals, parallel facts are familiar to all. Not only the forms and constitutions, but the habits, of horses, oxen, sheep, pigs, fowls, have become different from what they were in their wild state. In the various breeds of dogs, all of them according to the test of species derived from one stock, the varieties of mental character and faculty permanently established by mode of life, are numerous; and the several tendencies are spontaneously manifested. A young pointer will point at a covey the first time he is taken afield. A retriever brought up abroad, has been remarked to fulfil his duty without instruction. And in such cases the implication is, that there is a bequeathed tendency for the psychical changes to take place in a special way. Even from the conduct of untamed creatures, we may gather some evidence having like implications. The birds of inhabited countries are far more difficult to approach than those of uninhabited ones. And the manifest inference is, that continued experience of human enmity has produced an organic effect upon them—has modified their instincts—has modified the connections among their psychical states.
Thus then, of the two hypotheses, the first is supported by no positive evidence whatever; while the second is supported by all the positive evidence we can obtain. That the inner cohesions of psychical states are pre-adjusted to the outer persistencies of the relations symbolized, is a supposition which, if taken in its full meaning, involves absurdities so many and great that none dare carry it beyond a limited range of cases. That it is the true supposition in so far as this limited range of cases is concerned, no single piece of direct evidence can be given; seeing that only to one present at the creation of an organism is knowledge of pre-adjustment possible. So far as the facts are accessible, the supposition is so utterly untenable that no one entertains it; and so far as it is entertained, the facts are inaccessible and must ever remain so. On the other hand, the supposition that the inner cohesions are adjusted to the outer persistencies by an accumulated experience of those outer persistencies, is in harmony with all our positive knowledge of mental phenomena. It is a supposition that is confirmed by three separate methods of inductive inquiry. By the Method of Agreement; inasmuch as we have countless cases of states of consciousness whose cohesion is found to follow a repeated experience of the related phenomena to which they answer. By the Method of Difference; inasmuch as we have countless cases in which persons in other respects agreeing, differ in the cohesion between certain of these states of consciousness, as much as they have differed in their experiences of the answering phenomena. By the Method of Concomitant Variations; inasmuch as the degree of cohesion between states of consciousness, is found, other things equal, to vary as the number of times which the external relation to which they correspond has been repeated in experience. So conclusive, indeed, is the proof of this experience-hypothesis, that in respect to the great mass of psychical phenomena, no one doubts it. Only in respect to a particular order of psychical phenomena is the adverse hypothesis maintained. And though in so far as reflex actions and instincts are concerned, the experience-hypothesis seems to fail; yet, it is to be remembered that its seeming failure occurs only where the facts fail; and that in so far as the facts are accessible, they point to the conclusion that even automatic psychical connections result from the registration of experiences continued for numberless generations.
Such is the conclusion here adopted. The doctrine that the connections among our ideas are determined by experience, must, in consistency, be extended not only to all the connections established by the accumulated experiences of every individual, but to all those established by the accumulated experiences of every race. The abstract law of Intelligence being, that the strength of the tendency which the antecedent of any psychical change has to be followed by its consequent, is proportionate to the persistency of the union between the external things they symbolize; it becomes the resulting law of all concrete intelligences, that the strength of the tendency for such consequent to follow its antecedent, is, other things equal, proportionate to the number of times it has thus followed in experience. The harmony of the inner tendencies and the outer persistencies, is, in all its complications, explicable on the single principle that the outer persistencies produce the inner tendencies. Let it be granted that when two psychical states have once occurred in immediate succession, there results a certain tendency for the first, when it afterwards recurs, to be followed by the second—a proposition supported by an infinity of evidence; let it be granted that on every subsequent recurrence of this succession, a like effect is produced, and that by the accumulation of these effects the tendency becomes ever stronger—a proposition also supported by an infinity of evidence; let it be granted that this accumulation of effects goes on without limit, so as ultimately to make the tendency, as it must, insuperable—a proposition which is an unavoidable corollary from the previous one, and which is supported by all the facts accessible to us; let this be granted, and the adjustment of inner to outer relations is entirely explicable on the experience-hypothesis. All psychical relations save the absolutely indissoluble, are allowed on every hand to be determined by experience. Their various strengths are admitted by every one to be proportionate to the multiplication of experiences. It is an unavoidable corollary that an infinity of experiences will produce a psychical relation that is absolutely indissoluble. Though such infinity of experiences cannot be received by a single individual, yet it may be received by the countless succession of individuals forming a race. The individuals forming a race, severally transmit the constitutions they receive, with such modifications as their own habits of life produce in them. We have more or less distinct evidence, that induced tendencies in the nervous system, are transmitted along with induced tendencies in the other systems. And if we draw the induction, that the transmission of induced tendencies in the nervous system is a general law, we may conclude that all psychical relations whatever, from the absolutely indissoluble to the fortuitous, are produced by experiences of the corresponding external relations; and are so brought into harmony with them.
Thus interpreting the facts then, the inference is, that the growth of intelligence in general, like its growth in every individual, is dependent on the single law, that when any two psychical states occur in immediate succession, an effect is produced such that if the first subsequently recurs, there is a certain tendency for the second to follow it.
§ 181. From this law, if it be the true one, must be deducible all the phenomena of unfolding intelligence, from its lowest to its highest grades. Let us first observe how far the leading deductions correspond with the leading facts.
If the tendency of psychical states to follow one another results from their having before followed one another; and if each new succession in the same order adds an increment to this tendency; and if repeated successions in this order are consequent upon repeated experiences of the answering external relations; it follows that the psychical relations in any organism, must grow into correspondence with the particular class of environing relations with which it comes most in contact. The environment in general is infinite. The environment of each order of creature is practically more or less limited. And each order of creature has an environment which, besides being limited, is practically more or less special. The law implies then, that the psychical relations displayed by each order of creature, will be those which are most frequently repeated within the range of its experience. And this we know to be the fact.
Contemplating the animal kingdom at large, the first psychical relations established, must be those answering to the most prevalent environing relations of the simplest kind; which is just what we find. The stationary polype with outstretched tentacles, contracts on being touched. Now a creature that is not itself moving, can be touched only by something in motion. And this universal relation between collision and some moving body, is one of the first to be responded to. When a shadow passing across a rudimentary eye, is followed by a movement in the creature possessing that eye, the internal relation between the impression and the motion, corresponds with the relation between a passing opacity and a passing solidity in the environment; and this is one of the most general relations. Various other analogous cases will suggest themselves.
In the progress of life and in the progress of the individual, the adjustment of the inner tendencies to the outer persistencies, must begin with the simple and advance to the more and more complex; seeing that both within and without, the complex relations are made up of the simple ones, and cannot be established before the simple ones have been established. After some persistent relation of A to B in the environment, has, through accumulated experiences, generated a persistent relation between the psychical states a and b; and after some other persistent outer relation of C to D, has similarly generated a persistent inner relation c to d; then, if in the environment there exists any relation between the relations A to B and C to D, it becomes possible for repeated experiences to generate in the organism, a relation between a to b and c to d. But it is manifestly impossible for this to be done until the relations a to b and c to d have been themselves generated. This deduction too, we see to be in complete conformity with the facts, both of individual and of general evolution.
Further, it must follow, that the only thing required for the establishment of a new internal relation answering to a new external one, is, that the organism shall be sufficiently advanced to cognize the two terms of such new relation, and that being thus advanced, it shall be placed in circumstances in which it shall experience this new relation. Here also, there is a manifest harmony between the à priori inference, and the inference from observation. In our domestic animals there are constantly formed new psychical relations answering to such new external relations as have terms sufficiently simple to be cognized. And in human civilization we see the truth illustrated in the progress to wider and wider generalizations.
But the validity of these several corollaries will become more apparent as we proceed. That the phenomena of intelligence are all deducible from the one general truth, that when any two psychical states occur in immediate succession, an effect is produced such that if the first subsequently recurs there is a certain tendency for the second to follow—a tendency to which every repetition of the succession adds a further tendency—will be most clearly seen on tracing out the growth of intelligence under its chief aspects. Let us now pass on to these.