168 THE MONTESSORI METHOD
Milan who had followed the course in the Milan school of experimental psychology, seeing my material exposed, would recognise among it, measures of the perception of colour, hardness, and weight, and would conclude that, in truth, I brought no new contribution to pedagogy since these instruments were already known to them.
But the great difference between the two materials lies in this: The esthesiometer carries within itself the possibility of measuring; my objects on the contrary, often do not permit a measure, but are adapted to cause the child to exercise the senses.
In order that an instrument shall attain such a pedagogical end, it is necessary that it shall not weary but shall divert the child. Here lies the difficulty in the selection of didactic material. It is known that the psychometric instruments are great consumers of energy — for this reason, when Pizzoli wished to apply them to the education of the senses, he did not succeed because the child was annoyed by them, and became tired. Instead, the aim of education is to develop the energies.
Psychometric instruments, or better, the instruments of esthesiometry, are prepared in their differential gradations upon the laws of Weber, which were in truth drawn from experiments made upon adults.
With little children, we must proceed to the making of trials, and must select the didactic materials in which they show themselves to be interested.
This I did in the first year of the " Children's Houses " adopting a great variety of stimuli, with a number of which I had already experimented in the school for deficients.
Much of the material used for deficients is abandoned in the education of the normal child — and much that is