Multilevel Models for Intensive Longitudinal Data

Psychologists increasingly utilize diary-based methods to gather data reflecting study participants' experiences as they happen in day-to-day life. This method started with straightforward paper and pencil diaries that participants completed on fixed schedules. Over time, protocols have become more extensive, often comprising preprinted diaries with survey questions covering a wide array of experiential and contextual topics. The main objective of these data-gathering strategies is to achieve greater ecological validity in the measurement of psychological states, which can be realized through either infrequent administration of self-report surveys or via research made in decontextualized settings. These protocols convey information on the underlying psychological process that can only be unmasked through the analysis of intensive longitudinal measurements.