VII. ON SOME MINOR PSYCHOLOGICAL INTERFERENCES. A STUDY OF MISSPELLINGS AND BELATED MISTAKES. BY T. LE MABCHANT DOUSE. THE present subject may be introduced by a reference to the familiar chapter in the Theatetus where Plato compares the mind to an aviaiy, and knowledge, or rather know- ledges, to various birds and classes of birds which have been captured, and are secured therein. The recalling of a fact, or bit of knowledge, is represented by the laying-hold of some individual bird ; in which process it may sometimes happen that, while fancying we are taking the right one, we actually lay hold of a wrong one. Plato indicates his literal meaning by citing the microscopic fact that 5 + 7 = 12 ; and he discusses the mistake a man would make who should say that 5 + 7 = 11. To satisfy our present requirements, however, I must venture to expand the above simile. Let us suppose there- fore that, every day, and several times a day, a man, expert in the work, has to take from the aviary, one after another, a great number of birds of various species and sizes, and arrange them rapidly in differing series of appropriate cages in an order corresponding to preconceived or even impromptu ideas of his own ; and let a part of any one series consist, suppose, of cages which are labelled : M, B, Z, P, A, A, Q, A, D, B, S, . . . etc. appropriate to the individual birds : m, b, z, p, a, a, q, a, d, b, s, . . . etc. ; suppose further (although this is a detail) that, as man and aviary are inseparable, the cages move along from right to left, on his left hand, as fast as he can fill them, so that he works upon them from left to right ; then (and especially if M, B, Z, etc., form a late section of any series, so that the man's attention has begun to flag) it may be expected, for reasons which will appear below, that he will make mistakes
