ABSTRACT
One of the results that show most clearly the interest felt by boys for machines and the original mental reaction of any child when questioned on the subject, is the synchronism of ages marking the correct explanation of a bicycle in the various towns where we collected our material. In Paris and Geneva in particular, 8 is the average age of the boys who can give a complete explanation of this mechanism, supported by a spontaneous drawing. Little girls are naturally two or three years behind in this domain, for lack of interest in the question, and we shall therefore not mention them in the following pages.
