MENTAL CHARACTERS IX MAX 165 



however, now clearly recognise the inheritance of 

 mental traits. That mental traits are inherited in 

 animals has been clearly shown in one case by Castle, 

 who proved that in crosses between wild and tame 

 rats wildness is transmitted by the father to offspring 

 who have never .seen their father or had experience 

 of any behaviour but that of their tame mother. 

 Those who deal with psychological tests of such 

 animals as rats and mice soon learn to recognise 

 individual differences in psychology which make 

 the simple tests of efficiency, such as maze-running, 

 appear entirely inadequate unless careful allowance 

 is made for such temperamental differences. 



Modern psychology has developed in two directions, 

 which tend to make it more biological and are of 

 interest in connection with the present discussion : 

 (i) The theories of Freud and Jung dealing with the 

 formation of mental complexes, unconscious sup- 

 pression, mental conflicts, etc., and tending to show 

 that mental experiences very early in life, and quite 

 unperceived at the time, ma}^ have a profound in- 

 fluence on the later mental development ; (2) be- 

 haviourism, which has grown out of the purety 

 zoological experimental study of animal behaviour, 

 from protozoa to the anthropoid apes. The second 

 phase need not particularly concern us here. Avery 

 good summary of the Freudian phase has been written 

 by Tansley (1920). Instead of man being the rational, 

 thinking being the older psychology pictured him, 

 his mentality is seen to be built up on a mass of 

 instincts inherited from his animal ancestry, giving 

 him tendencies or instincts which constantly require 

 to be altered or repressed under the conditions of 

 civilised life. When not repressed, he acts first, and 

 rationalises his action afterwards. This repression, 

 often unconscious, ma}' lead to subconscious mental 

 conflicts and other difficulties. Kempf (1921) shows 



