The study of the brain has also had an indirect influence upon psychology through the strong impulse which it gave to psychiatry. The knowledge gained in the study of the abnormal mind gave a new insight into the processes of the normal mind. And since psychiatrists most often came into contact with the highly complex mental states, such as emotion, intelligence, self-consciousness, the impulses which they gave to psychology were a happy supplement to those other influences which concerned chiefly sensation and perception.
During the last decades of the nineteenth century all these buds of a new psychology were--first by Wundt--grafted on the old stem and so united into an harmonious whole. They have rejuvenated the apparently dying tree and brought about a strong new growth. The psychology of the text-book and the lecture room has become a different science. The most conspicuous sign of this new conception of the science of the mind is the establishment of numerous laboratories exclusively devoted to psychological research.
In earlier times psychology was but the handmaid of other interests. Psychological research was not an end in itself, but a useful or necessary means to higher ends. Usually it was a branch or a servant of philosophy. Men took it up particularly in order to understand the foundations of knowledge, or how our conceptions of the natural world originated, and this again in order to draw metaphysical or ethical conclusions, to settle the controversy between idealism and materialism, to answer the question as to the relation of body and mind, to derive rules for a rational conduct of life, often also with the mere purpose of confirming views springing from some other source. Others took up the study of psychology with a practical aim, for example, in order to find out how to make the most of their lives, or how to improve their memories. It is, to be sure, greatly to be hoped that psychology will not entirely lose its connection with philosophy, as natural science has unfortunately done. At no time, indeed, has the practical importance of psychology, its great usefulness in education, psychiatry, law, language, religion, art, been more strongly felt, or given rise to more numerous investigations than at present. But it is now recognized that, here as elsewhere, it is more fruitful for the true and lasting advancement of philosophical ends, instead of always thinking of advancing them, to forget them for the time, and to work on the preliminary problems as if these preliminary problems were the only ones existing. And so psychology, formerly a mere means to an end, has come to be regarded as a special science, to which a man can well afford to give his full time and energy.