Synonyms: diary research, longitudinal study, experience sampling, camera study, self-reporting study
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Definition
A diary study is a research method where participants record what they do and how they feel over a set period, usually days to a few weeks. Entries can be text, photos, videos, or screen recordings, logged on a phone as things happen.
It is useful for studying habits, repeated tasks, routines, and changes in behavior over time. Because participants record their own experiences, the method relies on self-reported data.
Use cases
A single interview can miss what happens between sessions, especially when behavior changes from day to day.
Forgotten routines: Users say in an interview they budget "weekly." Their diaries show they check the app mainly on payday and after big purchases.
Multi-channel journeys: A car buyer moves between a website, a dealer visit, and a finance call over 3 weeks. Diary entries connect those separate interactions.
Changing attitudes: New users rate a fitness app highly on day 1. By week 2, their entries show motivation dropping as reminders stop.
How it's used in practice
Choose a logging protocol. Ask participants to log at set times, after specific events, or when prompted by a notification.
Recruit for commitment. Screen for people who can complete entries consistently, and recruit extra participants to account for dropouts.
Run a kickoff and trial day. Show participants how to use the tool and let them practice before the study begins.
Review entries during the study. Check submissions regularly and follow up when an entry raises a useful question or a participant goes quiet.
Close with interviews. Use participants' entries as prompts for a final debrief.
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Pro-tip: Ask participants to include a concrete detail in each entry, such as what they were trying to do, what happened, and what they did next. It gives you more to work with during analysis.
Challenges & limitations
Dropout and fatigue: Entries can become shorter or less frequent as the study continues.
Self-reporting bias: Participants may forget events, change what they record, or leave out experiences they consider unimportant.
Analysis load: 15 people logging daily for 2 weeks can produce 200+ entries to code and synthesize.
