Momentary Positive and Negative Affect Are Measured Differently Across Individuals

Studies on momentary affect typically use self-report measures to study within-person dynamics. However, it is rarely tested whether the key assumption of measurement invariance is met in these studies. We examined whether positive and negative affect measures were invariant across individuals and across time. Using a large multi-wave measurement burst design, we investigated measurement invariance within and across three experience sampling phases, covering a six-year time span in participants’ lives. The study included 581 individuals (12 to > 85 years) who reported their momentary positive (joyful, content, interested) and negative affect (downhearted, angry, anxious) across three measurement bursts. Each bursts involved six daily assessments on at least nine days over a three-week period (M = 54 assessments per participant). Our analyses revealed that there was minimal variation in loadings and intercepts across measurement occasions, supporting measurement invariance across time. However, the loadings varied substantially across individuals, indicating that the latent variables measuring momentary affect differed between individuals. This finding challenges the assumption that momentary affect is measured uniformly across individuals. We discuss the implications of these results and propose potential ways of addressing measurement non-invariance in this context. notReviewed other