The effect of serial day on the measurement of positivity and emotional complexity in diary studies

We study the effects of a diary's serial day (the number of days from the beginning of the study) on participants’ (n = 2022) reports about positive and negative affect (NA). We find that (1) the number of reported positive events and the number of reported negative events decrease with serial day; (2) positivity increases with serial day: Reported Positive Affect (PA) increases, and reported NA decreases; (3) emotional complexity—the tendency to differentiate between various types of emotions—decreases with serial day, both within and between affective dimensions. We attribute these effects to decrease in the effort exerted by participants in answering the diary questions, and suggest that these effects are consistent with the distinction between experienced and reported emotions and with a heuristic and biases perspective in which when effort decreases reported emotions regress to an easier-to-generate default response.