Understanding the P×S Aspect of Within-Person Variation: A Variance Partitioning Approach

Abstract

This article reviews a variance partitioning approach to within-person variation based on Generalizability Theory and the Social Relations Model. The approach conceptualizes an important part of within-person variation as Person × Situation (P×S) interactions: differences among persons in their profiles of responses across the same situations. The approach provided the first quantitative method for capturing within-person variation and demonstrated very large P×S effects for a wide range of constructs. These include anxiety, five-factor personality traits, perceived social support, leadership, and task performance. Although P×S effects are commonly very large, conceptual, and analytic obstacles have thwarted consistent progress. For example, how does one develop a psychological, versus purely statistical, understanding of P×S effects? How does one forecast future behavior when the criterion is a P×S effect? How can understanding P×S effects contribute to psychological theory? This review describes potential solutions to these and other problems developed in the course of conducting research on the P×S aspect of social support. Additional problems that need resolution are identified.

Keywords: G theory; Person × Situation; P×S; RRT; SRM; within-person variation.

FIGURE 1

P×S profiles from Table 1. Each of three persons is indicated by P₁ – P₃ and each of three situations is indicated by S₁ – S₃.

FIGURE 2

P×S profiles of supportiveness (PSS) covary with P×S profiles of positive affect (PA). Each of three persons is indicated by P₁ – P₃ and each of three situations is indicated by S₁ – S₃.

FIGURE 3

P×S effects emerge when persons weigh providers’ traits differently in forming support judgments. N = neuroticism; E = extroversion; O = openness; A = agreeableness; C = conscientiousness.