Cortical evoked potential, personality, and intelligence.

The averaged cortical evoked potential (CEP) was measured from 296 male subjects in two studies and was correlated with scores on intelligence and personality tests. For both studies, auditory stimuli were used with bipolar electrode placement to the Cz and T3 scalp positions. In the first study, with 84 subjects, stimulus intensity was 95 dB (all dB readings re 20 muN/m2). Intelligence was measured with the Mill Hill Vocabulary Scale and personality with H. J. Eysenck's PEN questionnaire. The second study, with 212 subjects, used additional stimuli at 75 dB and 55 dB. Intelligence was measured with the Ravens Progressive Matrices. State anxiety and other state measures at the time of testing were also taken. Neither study found any relation between the CEP and IQ or personality. However, more bored subjects showed larger CEP amplitudes. The results are discussed in terms of Ertl's neural efficiency hypothesis and Eysenck's arousal theory of personality.