With these illustrations our notice of mental defects may terminate. The more complex troubles, the various insanities, manias, phobias, etc., can not be briefly described. Moreover, they are still wrapped in the profoundest obscurity. To the psychologist, however, there are certain guiding principles through the maze of facts, and I may state them in conclusion.
First, all mental troubles involve diseases of the brain and can be cured only as the brain is cured. It does not follow, of course, that in certain cases treatment by mental agencies, such as suggestion, arousing of expectation, faith, etc., may not be more helpful here, when wisely employed, than in troubles which do not involve the mind; but yet the end to be attained is a physical as well as a mental cure, and the means in the present state of knowledge, at any rate, are mainly physical means. The psychologist knows practically nothing about the laws which govern the influence of mind on body. The principle of Suggestion is so obscure in its concrete working that the most practised and best-informed operators find it impossible to control its use or to predict its results. To give countenance, in this state of things, to any pretended system or practice of mind cure, Christian science, spiritual healing, etc., which leads to the neglect of ordinary medical treatment, is to discredit the legitimate practice of medicine and to let loose an enemy dangerous to the public health.
Moreover, such things produce a form of hysterical subjectivism which destroys sound judgment, and dissolves the sense of reality which it has taken modern science many generations to build up. Science has all along had to combat such wresting of its more obscure and unexplained facts into alliance with the ends of practical quackery, fraud, and superstition; and psychologists need just now to be especially alive to their duty of combating the forms of this alliance which arise when the newer results of psychology are so used, whether it be to supplement the inadequate evidence of "thought-transference," to support the claims of spiritualism, or to justify in the name of "personal liberty" the substitution of a "healer" for the trained physician. The parent who allows his child to die under the care of a "Christian Science healer" is as much a criminal from neglect as the one who, going but a step further in precisely the same direction, brings his child to starvation on a diet of faith. In France and Russia experimenting in hypnotism on well persons has been restricted by law to licensed experts; what, compared with that, shall we say to this wholly amateurish experimenting with the diseased? Let the "healer" heal all he can, but let him not experiment to the extremity of life and death with the credulity and superstition of the people who think one "doctor" is as good as another.
Second, many experts agree that diseases of the mind, whatever their brain seat may be, all involve impairment of the Attention. This, at any rate, is a general mark of a deranged or defective mind. The idiot lacks power of attention. The maniac lacks control of his attention. The deluded lacks grasp and flexibility of attention. The crank can only attend to one thing. The old man is feeble in the attention, having lost his hold. So it goes. The attention is the instrument of the one sort of normal mental activity called Apperception, and so impairment of the attention shows itself at once in some particular form of defect.
Third, it is interesting to know that in progressive mental failure the loss of the powers of the mind takes place in an order which is the reverse of that of their original acquisition. The most complex functions, which are acquired last, are the first to show impairment. In cases of general degeneration, softening of the brain, etc., the intelligence and moral nature are first affected, then memory, association, and acquired actions of all sorts, while there remain, latest of all, actions of the imitative kind, most of the deep-set habits, and the instinctive, reflex, and automatic functions, This last condition is seen in the wretched victim of dementia and in the congenital idiot. The latter has, in addition to his life processes and instincts, little more than the capacity for parrot-like imitation. By this he acquires the very few items of his education.
The recovery of the patient shows the same stages again, but in the reversed direction; he pursues the order of the original acquisition, a process which physicians call Re-evolution.
CHAPTER VI.
HOW WE EXPERIMENT ON THE MIND—EXPERIMENTAL PSYCHOLOGY.
In recent years the growth of the method of experimenting with bodies in laboratories in the different sciences has served to raise the question whether the mind may not be experimented with also. This question has been solved in so far that psychologists produce artificial changes in the stimulations to the senses and in the arrangements of the objects and conditions existing about a person, and so secure changes also in his mental states. What we have seen of Physiological Psychology illustrates this general way of proceeding, for in such studies, changes in the physiological processes, as in breathing, etc., are considered as causing changes in the mind. In Experimental Psychology, however, as distinguished from Physiological Psychology, we agree to take only those influences which are outside the body, such as light, sound, temperature, etc., keeping the subject as normal as possible in all respects.