GENETIC METHOD IN PSYCHOLOGY.

29

thought, to discover what was innate and proof against the solvent of sceptical doubt. Locke and his followers, Berkeley and Hume, carried out a far more extensive analysis of ideas with the view of showing that they could be all traced back to elements of experience. The clearer differentiation of psychology from philosophy effected by the work of Hartley and James Mill led to the methodical use of analysis as the proper instrument of psychological research. The complementary work of systematic synthesis, that is, of setting out with the elements of sensation and building up the various complex products, naturally added itself to this as soon as a sufficient knowledge of the elements and of the laws of their combination was reached. Thus in Dr. Bain's system of psychology we find a fairly systematic attempt to expound the course of mental development. It is, however, only since the idea of biological development has come to be applied to mind that the synthetic treatment of the subject has become completed. The importance of this synthetic treatment of the subject is very well illustrated in Mr. Herbert Spencer's system of Psychology. In Germany it was Beneke who first systematically attempted a genetic treatment of mind on a positive or scientific basis. Discarding the metaphysical presuppositions with which Herbart had set out, and postulating only certain primordial modes of sensibility, Beneke tried to trace out the process of psychical formation in its several directions.

§ 14. Reference to the External Conditions of Psychical Events: the Physiological Method in Psychology. Thus far we have regarded the aim of the psychologist as the construction of a theory of the activities and the development of the human mind by a consideration merely of the mental life as something complete in itself or self-contained, and without any reference to extraneous conditions. And there is no doubt that it is possible in this way to determine up to a certain point the general course of psychical events.1 At the same time it must be evident from what has been said above that a complete scientific explanation of the mental life of the individual requires us to travel beyond the bounds of this life, and to take note of its connexions with other operations and series of operations.

And here, it is evident, there comes in that reference to the bodily organism with which, as has been pointed out, the activities of mind are so closely united. Modern psychology, though claiming for the processes of conscious life a place apart from physical actions, fully recognises that the former are vitally conjoined with and influenced by the latter. The course of the mental life of the individual, though capable by a process of abstraction of being detached from the bodily

1 This is sufficiently evidenced by Ward's recent treatment of the subject in the Encyclopædia Britannica.

organism and studied as a process complete in itself, remains after all from its commencement to its close interwoven into the sum of activities which constitute the life of the organism. Hence the psychologist must continually supplement his introspectively acquired knowledge of the psychical process itself by a reference to the determining and modifying conditions which exist in the bodily organism, and more particularly the organs composing the Nervous System.

This reference to nervous conditions is a necessary completion of the work of psychological analysis. To analyse any phenomenon we must include in our view all the co-operating circumstances or conditions which help to determine it. Such an inclusion of nervous conditions is specially necessary in giving an account of the more elementary psychical phenomena as sensations and conscious movements. It is evident that the sensations of pressure, light, colour, etc., which constitute the material of all our knowledge of external objects, can only be accounted for by a reference to the bodily mechanism, or organs of sense, by the medium of which they are excited. A consideration of the physiological conditions of sensation may indeed in certain cases help us to anticipate the results, and so to widen the scope, of subjective analysis, by resolving what seem to us perfectly simple sensations into simpler components.

§ 14a. Psycho-physical Experiment. The importance of thus combining psychological and physiological research is abundantly illustrated in the new domain of experimental psycho. physical research already referred to. It is by help of a careful observation of physical processes that experiment has acquired its present firm footing in psychology. Such experimental research into the facts of consciousness brings with it the great advantages of special physical apparatus, enabling us to esti mate exceedingly small variations in the quantity of the force or stimulus acting on the organism, and in the duration of psycho-physical processes. Hence it has tended to give to psychical research something of that exactness the absence of which Kant deplored.

Psycho-physical research in its widest sense embraces a good deal of what is called experimental physiology, e.g., electrical stimulation of different areas of the cortex of the brain with a view to determine correlated mental functions.

PSYCHO-PHYSICAL RESEARCH.

31

In a narrower sense "psycho-physics" concerns itself specially with experimental inquiry into the psycho-physical processes in Sensation. This branch connects itself closely with the physiology of the sense organs. Thus one aim of these experiments has been to determine precisely how changes in the intensity or strength of a sensation vary with changes in the quantity of the external stimulus and the intervening nervous process. This series of investigations was started by the famous labours of Weber, supplemented by those of Fechner who named this department psycho-physic. Similar inquiry has been directed to the connexion between the quality of sensation and changes in the mode of neural excitation. As already suggested these researches go to eke out the purely subjective analysis of sensation. Thus a great deal of experimental work has been directed to resolving more complex sense-phenomena, e.g., space-perceptions of the eye, perceptions of musical clang, into their constituent elements.

Another important line of experimental investigation into psycho-physical phenomena is marked off by the name "Reaction-time," or the experimental determination of the duration of psycho-physical processes. These researches consist in determining, by means of very special apparatus, the precise interval-measurable in thousandth parts of a second-between the occurrence of a sense-signal, e.g., a sound, and the motor reaction or movement which the subject of the experiment has to carry out immediately on perceiving the same. This line of investigation has proved particularly fertile in helping us to understand the duration, not merely of the elementary processes of sensation itself, but of higher mental operations (e.g., comparison, choice) which can be easily interposed in this kind of experiment.1 Other lines of psycho-physical experiment have to do with the determination of the time-interval which can be most accurately estimated and reproduced, with the number of consecutive impressions, e.g., sounds, which can be temporarily retained or embraced as a single series or group, and so forth.2

1 A short account of reaction-time experiments is given by James, Principles of Psychology, i. p. 85 ff.; cf. Ladd, Elements, part ii. chap. viii.

2 On the general aim of psycho-physical research, see Wundt, Physiol. Psychologie, i., Einleitung, i.; Ziehen, Leitfaden der physiol. Psychologie, pp. 1 and 2.

§ 14b. The Evolutionist's Extension of the Genetic Method. It is to be noted that such a reference to the concomitant physiological processes enables the psychologist to greatly extend the range of the genetic or historical method as applied to the individual mind. While the older psychologists set out with the first vague manifestations of the individual mind as an absolute beginning, the modern evolutionist views the nervous organisation of the infant as embodying the results of ancestral mental experience. This theory sets out with the fact that the repeated carrying out of a certain line of action modifies the nervous structures so as to produce an organic disposition to that particular mode of action, an effect which is illustrated in what we call habit. By supposing such organic registrations to be transmissible by heredity the evolutionist reasons that the child inherits from its series of progenitors, woven into the texture of its nervous system, a number of dispositions representing ages of ancestral experience. In this way we are able to view the mental life of the individual as conditioned by, that is, genetically related to, the larger life of the species and of its predecessors in the zoological series.1

The doctrine of evolution enlarges the psychologist's "genetic method" in another way. Darwin and his followers have familiarised us with the idea that particular organic variations which are found to be useful tend by natural selection to become permanent. This theory enables us to introduce a quasiteleological point of view into the organic world, and to interpret what we find to be permanent as owing its stability to its utility or adaptation to life-circumstances. Applying this conception to those psycho-physical arrangements which constitute the common instinctive base of our mental life, the psychologist can suggest how, in the course of the evolution of man and his progenitors, certain arrangements may have been built up. This biological or teleological view of psychical phenomena will be illustrated from time to time in the course of our exposition.

1 This is the common supposition of evolutional psychologists, though, as we shall see by-and-by, it is a matter of dispute whether any acquired characters, and consequently any results of experience, can be transmitted by heredity. It is important to add that this hypothesis does not imply that the child has antecedently to its experience conscious states which are a kind of vague recalling of ancestral experience, but only that it has certain organic arrangements which prepare the way for particular psychical processes when individual experience is added.

EVOLUTION AND PSYCHOLOGY.

33

§ 14c. Limits of Physiological Explanation. It is important to add, however, that while the psychologist is thus compelled to refer to the bodily organism if he would give a complete account of all the circumstances which condition psychical phenomena he cannot make such a reference a substitute for properly psychological explanation. It follows from the essential disparity of psychical and physical phenomena, emphasised in the last chapter, that we cannot in any case derive a fact of consciousness from the nervous actions which are its physical substratum. This applies even to that elementary department of mental phenomena, sensations, in which the reference to nervous conditions is most obvious and inevitable. In naming the nervous processes which precede and accompany a sensation of taste or smell, we do not look on this last as a mere transformation of the molecular movements of which the first are supposed to consist. We cannot account for the specific nature of any sensation, whether of taste, hearing or other sense, by the fullest knowledge of its nervous conditions. As a mode of psychosis it is something wholly foreign to the world of moving masses and particles with which physical investigation is concerned. To this it must be added, that with respect to the higher mental phenomena, as thought and volition, we have only a vague and incomplete knowledge of the nervous conditions involved. So that physiology gives the psychologist less and less help as he advances from the elementary facts of consciousness to its more complex forms.

This position is by no means universally granted. It is obvious that those who, like Comte and Dr. Maudsley, would include psychology in physiology tacitly deny that there is any radical disparity between psychical phenomena, our conscious sensations, thoughts and feelings, and the physical movements which constitute the actions of the bodily organism. One recognises the same tendency in those who, while they concede an independent existence to psychology, are given to introducing physiological considerations in place of properly psychological ones. Lastly, this tendency is betrayed in a less manifest form in the idea put forth by Horwicz and others that our psychological inductions are empirical and not ultimate laws, and that they will have hereafter to be connected with and deduced from more general biological principles.1

1 On the limits of physiological explanation in psychology, and the question of Lesolving psychological into physiological laws, see J. S. Mill, Logic, bk. vi. chap. iv. § 2; Brentano, Psychologie, buch i. cap. iii. § 4 and following.