SESSION 1 PAPER 4

Known in behaviour as "habituation" and in perception as "adaptation", it has been recognised from time immemorial yet still lacks explanation. Only recently Sharpless and Jasper (1956, ref. 10) could say "Habituaticn... has yet to be explained by any known neurophysiological principles". A review of the subject need not be given here as it has been well reviewed by Humphrey (1933, ref.6), Harris (1943, ref. 5), and Thorpe (1956, ref. 11). On one important matter they are agreed: habituation of typical form occurs in almost every form of life; in particular it appears as readily in forms having no neural apparatus as in the forms having a well developed brain. Amoeba shows it as freely as does the cat. The phenomenon evidently does not depend on specifically neurophysiological details. Its origin must lie in some property of much wider occurrence. The possibility of "fatigue" as an explanation must be rejected.