Abstract
<p>Ecological Momentary Assessment (EMA) is often praised for its ecological validity, under the assumption that change observed in EMA data reflects change in the underlying constructs, independent of study participation. However, participation itself may threaten ecological validity as participants’ involvement in an EMA study may already alter their experiences, behavior or responses. Existing research on such participation effects has primarily documented their occurrence rather than explained the mechanisms through which they arise. To advance this understanding, we developed a taxonomy of potential sources of (measurement-induced) change in EMA data. This taxonomy includes increased reflection on assessed constructs (i.e., measurement reactivity), alterations to daily routines (i.e., measurement interference), shifts in how participants interpret items or response scales (i.e., reconceptualization or recalibration), practice in gauging internal states (i.e., improved introspection), and declining participant engagement (i.e., heightened careless responding or reduced compliance). Identifying these distinct sources of change highlights the need for systematic investigation of their impact and the development of targeted mitigation strategies. We therefore outline a research agenda focusing on assessing and experimentally manipulating each source of measurement-induced change in isolation. In sum, this paper aims to initiate a collective effort among EMA researchers to clarify the mechanisms by which study participation shapes data, and to safeguard EMA’s promise of ecological validity. Keywords: experience sampling methodology, measurement reactivity, (ecological) validity, response shifts, careless or insufficient effort responding</p>