Fig. 2

Overview of questionnaires prior and during sessions/phases of the study. Numbers in parentheses correspond to their respective assessment instance, starting from (1) for the first time, (2) to the second time, etc. Details on the materials can be found in Supplement A. Some important concepts that have not been elaborated on in the main text are, however, clarified here. Photo/WhatsApp message forgotten: in case participants forget to take a picture/send a WhatsApp message before/while performing their target behavior, they can provide the date(s) manually at the end of each week, such that the frequency measure can be adapted. To ensure that we will observe participants’ natural adherence without the influence of daily reminders, we refrain from asking participants whether they have taken a photo/send a WhatsApp message on a daily basis. Habit experience refers to the extent to which the act of walking/performing the chosen behavior on a daily basis is considered to be a habit by the participants, as indicated on a scale ranging from ‘not at all’ to ‘very strongly’. Secondary goal refers to a subordinate goal that individuals may have when their goal/plan entails inhibiting an old habit by replacing it with something positive/good. For instance, a person may want to reduce her snacking behavior (secondary goal) by eating an apple after dinner (primary goal), rather than crisps