Properties of psychological variables at the mean or variance level can differ between persons and within persons across multiple time points. For example, cross-sectional findings between persons of different ages do not necessarily reflect the development of a single person over time. Recently, there has been an increased interest in the…

Given the longitudinal nature of L2 grit, the use of conventional research methodologies with cross-sectional data to examine the validity of L2 grit scale seems inadequate. The present research was an attempt to extend the domain-specific phase of research on L2 grit, with the pursuit of long-term goals at its core, into a dynamic one. Thus, we…

This study examined the extent of measurement invariance of the Basic Psychological Needs in Exercise Scale responses (BPNES; Vlachopoulos & Michailidou, 2006) across male (n = 716) and female (n = 1,147) exercise participants. BPNES responses from exercise participants attending private fitness centers (n = 1,012) and community exercise programs…

A component analytic method for analyzing multivariate longitudinal data is presented that does not make strong assumptions about the structure of the data. Central to the method are the facts that components are derived as linear composites of the observed or manifest variables and that the components must provide an adequate representation of…

Two sources of inconsistency were separated by reanalyzing data from a major study on short-term consistency. Little evidence was found for generalizability or behavioral predictability. Results supported the assumption that measurement error from short-term fluctuations is not due to systematic individual differences in response consistency.…