Estimating Modulator Indices and State Liabilities

An extension of the familiar factor analytic model which deals with traits has been proposed to enable it t o fit the psychological theory of modulation of behavior by ambient situations which change individuals' state levels and role involvements (Cattell, 1963). The present paper gives more substance to this development, defining more precisely the basic assumptions in the new concepts and setting out the procedures for calculating the main new parameters. Most important among the latter are (1) the modulator values for each ambient situation, (2) the characteristic individual state liabilities, and (3) the change in the group state level as related to the individual state changes. This model is also part of a development for integrating the traditional interests of psychometrists, centered on individual differences, with the tradi- tion interests of experimentalists (researchers on processes, such as learning and perception) centered on changes in group means. It is suggested that this model brings to practical experimental work with concepts of mood, role, and the measurement of ambient-situations the precision t o which we have been accustomed in individual difference psychometry in a way not previously pos- sible in this domain.