Boris Sidis

“ Turning now to association by similarity we find that the relations of the elements are somewhat more complex than in that of contiguity. Where mental life is complex and where there are present many different trains of ideas and images, there will be a tendency for them to cross and intersect at many points. The course of a given train of ideas and images instead of running in its habitual line will tend to become deflected along other lines and give rise to that particular form of association of representative elements known as association by similarity and contrasts. ”

“ The relation of likeness is present not only in trains of representations, but also in presentations or in what is termed by us psychic compounds. Thus twins we say look alike, so do eggs, so do animals of the same species; a picture say of a landscape looks like the actual landscape, and a portrait or statue resembles the original. In all these examples the likeness is constituted by the sensory elements common to the presented psychic compound. ”

“ Representative elements form what may be characterized as mental trains. The elements of a mental train are connected by relations of contiguity, resemblance, and contrast. Association by contiguity depends on the frequency, recency with which the elements have been associated, while resemblance and contrast may be regarded as two or more mental trains of representative elements associated by contiguity, crossing and intersecting in a few points, in other words having some element in common. ”