Baselines Matter: Cardiovascular Baseline Procedures in Affective Psychophysiology.

A baseline is necessary to define biological reactivity in psychophysiological research. However, the conceptualization and implementation of baseline measurements are often underdescribed and weakly justified. This poses a problem because poor baseline decisions have the potential to introduce noise, reduce comparability across studies, and bias interpretations of data. In this article, we focus on laboratory studies using cardiovascular measures in affective psychophysiology. Motivated by substantial variation and limited reporting of baseline procedures, we examined within-baseline stabilization in two studies. Study 1 analyzed 1593 baseline sessions from 1310 participants in the POPANE and CEPAV datasets. Study 2 assessed generalizability using data from 2395 participants collected in a U.S. laboratory. Findings suggest that although different cardiovascular indices may stabilize differently during a 5-min baseline, this procedure is a reasonable, pragmatic choice. More broadly, findings highlight the need for stronger justification, standardization, and reporting of baseline procedures in psychophysiological research.