Date of this Version
Psychology is distinguished from its brethren sciences of biology and sociology in that its main concern is with behavioral and mental processes of the individual (Zimbardo, 1992). Traditional study of personality and intelligence has focused on individual differences--searching for traits or relatively stable characteristics along which people differ (Eysenck & Eysenck, 1985; Howard, 1993). This line of research is based on the assumption that an improved scientific understanding of the nature of psychological functions can be achieved only by taking into account information about overall levels of performance and between-subjects variability and covariability. While the emphasis in individual differences research has been on multivariate procedures, experimental psychology has been almost exclusive in its focus on univariate designs. Multivariate research is closely linked to the development of psychological measuring instruments which are widely used in educational, industrial, and clinical settings. More recently, psychobiological explanations of personality and ability constructs have been sought (e.g., Zuckerman, 1991), opening the way for more sophisticated understanding of the neuropsychological and neuroendocrinological mechanisms underlying personality and ability traits. Hence, it is possible to claim that studies of intelligence and personality based on these combined approaches have made a more significant contribution to our social life in general than many other areas of psychological research (cf. Goff & Ackerman, 1992).