The New Person-Specific Paradigm in Psychology

Abstract

Most research methodology in the behavioral sciences employs interindividual analyses, which provide information about the state of affairs of the population. However, as shown by classical mathematical-statistical theorems (the ergodic theorems), such analyses do not provide information for, and cannot be applied at, the level of the individual, except on rare occasions when the processes of interest meet certain stringent conditions. When psychological processes violate these conditions, the interindividual analyses that are now standardly applied have to be replaced by analysis of intraindividual variation in order to obtain valid results. Two illustrations involving analysis of intraindividual variation of personality and emotional processes are given.

On the validity and generality of transfer effects in cognitive training research

“…For example, interpretation of latent factor models at the level of single individuals relies on the implicit assumption of ergodicity (i.e. the assumption that the data structure of multiple assessments of a single individual corresponds to the data structure of single assessments of multiple individuals; see Molenaar & Campbell, 2009). This means that measurement invariance does not only need to hold for the between-person structures across measurement occasions, but also for each individual, which could only be tested by measuring individuals multiple times to analyze their individual within-person structures.…”

Revisiting the lack of association between affect and physiology: Contrasting between-person and within-person analyses.

“…These seemingly opposite results highlight that the nature of relationships between variables at one level cannot be assumed to exist at another (i.e., the ecological fallacy; Kramer, 1983;Portnov, Dubnov, & Barchana, 2007). This issue has been explored in the context of aging and cognition (e.g., Sliwinski & Mogle, 2008) and more generally discussed as a theoretical/analytic issue (e.g., Molenaar & Campbell, 2009), underscoring the need for more careful attention and exploration.…”

Real-Time Associations Between Engaging in Leisure and Daily Health and Well-Being

“…The ecological fallacy states that relationships between variables at one level (e.g., between individuals) cannot be assumed to exist at the same magnitude and direction at another level (e.g., within individuals) (for discussion of the different applications of between-and within-person models, see [19]). Thus, returning to leisure, it cannot be assumed (despite the plausibility of such a perspective) that the between-person data and analyses suggesting positive effects of leisure on health indicate support for the theorized in-themoment, within-person associations that are proposed to underlie leisure's positive effects.…”