The wobbly bits of development: Variability, fluctuations, and synchrony as temporal markers linking temperament and psychopathology

Abstract

Temperament traits are early appearing and relatively stable phenotypic profiles of behavior that are present across space and time. This definition invariably reflects the timescale imposed when gathering repeated measures of our variables of interest and our reliance on aggregate, mean-level values. However, if the time scale of observations is shortened, and the frequency of observations increased, underlying or latent fluctuations and variability may emerge. Embedding short-term fluctuations into slower developmental trajectories may improve our understanding of behavior in the moment, while also strengthening prediction. Researchers should embrace a more granular time scale in research, incorporating new technology and analytical approaches, enhancing our ability to capture developmental change. This review illustrates with the temperament literature how shifting time scales can provide new insight into social, behavioral, and cognitive processes across development.

Keywords: Intraindividual variability; development; fast timescales; socioemotional behavior; temperament.

Figure 1.

Hypothetical distribution of performance at different timescales. Infant performance on a gold standard A-not-B task is presented monthly, represented in the solid black line. While the aggregate performance is relatively smooth as infants move from floor to mastery, there is underlying levels of variability. The blue lines represent variation in performance from trial to trial, and in shorter re-testing intervals. As can be noted, variability is greater in ‘active’ developmental phases, rather than at floor and ceiling.