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system or sense organs, and that, in these cases, the whole basis of mentality may be
so altered as not to be comparable with any scale derived from the study of normal
children. Defective vision, and again defective hearing, affect the appreciation of
his environment by the subject, and also interfere with the due comprehension of
any problem set before him. Paralyses profoundly vary not only the nature of the
motor output, but the whole of the mental re-actions, while such conditions as
meningitis, encephalitis, and the like, alter the whole basis of feeling and willing.
There may, therefore, in such cases, be successes in relatively advanced tests and
failures in relatively simple tests. In some cases of brain damage, the mentality
may be underestimated, but, in the majority of cases, a failure to appreciate the
limitations and risks imposed by the injury leads to a misleading optimism as to the
future. This is particularly true of children suffering from epilepsy or from some
forms of paralysis due to brain injuries received at the time of birth.
An important part of the clinical examination consists in the application of
mental tests which afford an opportunity of noting the re-actions of the subject
to definite problems, his power of perceptions, the continuity of his attention, the
extent to which he plans or works by chance, the character of his mental associations
and various other characteristics. Two fundamental biological features separating
man from the animals are his powers of using language and of employing tools to
assist his efforts. These features must be kept in the foreground of any investigation.
Aptitudes of a practical nature are investigated by means of performance
tests, of which a large variety exists. In the early stages, these consist of simple
movements, such as clapping the hands, or catching a ball. Slightly more complex
is the carrying out to order of definite actions, such as simple drill movements.
In the course of these, an estimate may be made of the power of understanding
spoken language and the control of movements. Of great importance is the degree
of development, the power of control and of co-ordinated action of the finer muscles,
especially those of the eyes, of the lips, of the larynx, and of the hand, which are
used in human expression. The powers of articulation, the movements of the eyemuscles,
the facial expression or its absence, the use of simple tools, such as scissors
or needle and thread, the performance of simple actions, such as buttoning and unbuttoning
garments, all are capable of throwing light upon the condition of peculiarly
human muscles of expression and the nervous and mental mechanisms controlling
their action. Atrophy of these muscles, as evidenced by direct examination, and
lack of power of co-ordination, as evidenced in their use, are valuable characters from
the diagnostic standpoint.
Perception is investigated by such tests as naming or matching colours, recognising
simple objects and the like. Recognition and recollection are tested
by the child being shown a picture and asked to say what he sees, or by giving him
a series of cards such, for example, as are used in the common nursery game of
animal grab and asking him to pick out the dogs, cats or other subjects depicted,
or by asking him "What does a dog or cat say?" Discrimination is tested by
asking the child to say which is the longer of two sticks or lines; which is the larger,
the nearer or the farther off of a series of boxes, or which of two apparently similar
boxes is the heavier. Appreciation for form and powers of planning are tested
by asking the subject to replace the blocks in a form board, various patterns of which
exist, adapted to the needs of children of different ages. The point which is noted
here is not so much the success or failure, as the method of attacking the problem.
The lower grades of defectives almost always work in a haphazard manner, constantly
repeating the same errors. Another method is to give the child a picture to build up
from a series of blocks such as are commonly used in the nursery. At a more advanced
stage, the picture may be complete save for certain blocks and the subject
offered a choice of blocks to complete the whole.
Social activities are tested by giving the child one or more simple errands to