Applied individual differences research and its quantitative methods

Applied individual differences research is one of the few branches of psychological science that have systematically amassed a coherent body of empirical knowledge withstanding the test of time. Furthermore, it has exemplified how practice can facilitate basic science. While examining relatively stable behavioral attributes (abilities, personality, vocational preferences), which form the bases of their longitudinal forecasts pertaining to broad behavioral patterns and proclivities, differential psychologists appear to have uncovered keys to behavioral development. They also have contributed to a better understanding of human diversity and its many unique (''idiographic'') manifestations. This issue of the journal tells a story about this domain of knowledge; its history in facilitating practice in educational, clinical, and counseling psychology; and its role in personnel development and selection in business, industry, and the military. Some ways in which individual differences dimensions converge on other psychological viewpoints (phenomenology, Skinnerian behaviorism) are reflected, as is their bearing on theories of human development more generally. When examining human behavioral phenomena from a psychological point of view, taking a multifaceted (individual differences) approach appears to be critical; this is especially important when designing opportunities and policies for positive development in clinics, in schools, at work, and in society at large.