Recently，the approach between Pavlov's typology and Eysenck's personality dimensions has attracted interest. Eysenck (1966) pointed to certain similarities between the concept of extraversion-introversion and Pavlov's theory of nervous system type. He said that “the weak personality type appears to resemble the introvert，the strong personality type the
extravert". The results obtained by many experimenters were discussed in this paper; despite Eysenck's suggestion，there appears to be only apartial correspondence between extraversion-introversion and Pavlov's strong and weak types，but there appears in Gray's hypothesis that the dimension
of strength of the nervous system and that of introversion-extraversion are identical both being based upon level of arousal or arousability to be suffcient evidence to be worth devoting serious attention to.