Longitudinal Research · Self-Report · Behaviour Over Time
Diary Studies That Capture What Actually Happens
Interviews tell you what people remember. Diary studies show you what actually happened, logged in the moment, across the days and weeks that a single conversation can never cover. We design and run diary studies for behaviour that is infrequent, private, or unfolds slowly, then turn the entries into findings you can act on.
Why run a diary study
Some behaviour cannot be reconstructed after the fact. It happens once every few days on no fixed schedule, it happens somewhere a researcher could never sensibly stand, or it changes shape over weeks in a way a single conversation flattens into "it kept happening." Asking someone to describe it from memory gets you a summary. Asking them to log it as it happens gets you the real thing.
A diary study puts the record-keeping in the participant's hands, at the time, in their own words. We handle the design, the recruitment, the reminders that keep people logging past the first few days, and the closing interviews that turn a pile of entries into an explanation. Read our full guide to what a diary study is for the detail behind how and when it works.
Diary study formats we run
From a short scheduled prompt to a full multi-cohort programme, we match the format and cadence to what you actually need to learn.
Scheduled Daily Diaries
A short prompt at fixed points, once a day or morning and evening. Easy for participants to build into a routine, and the format with the highest completion rate over several weeks.
Event-Contingent Diaries
An entry every time something specific happens: a symptom, a workaround, an error, a decision point. Catches irregular behaviour precisely, without asking for entries when nothing has occurred.
Photo Diaries
Participants photograph a moment, workspace, or artefact with a short caption. Effective for anything visual, and often surfaces detail that a written description leaves out entirely.
Voice & Audio Diaries
A spoken entry instead of typed text. Faster than writing when someone is tired or on the move, and captures tone and frustration that a typed note tends to flatten out.
App-Based Structured Diaries
Purpose-built diary tooling with push reminders, structured prompts, and clean export. Earns its cost once a study runs more than a week or two, or involves more than a handful of participants.
Diary + Follow-Up Interview
A closing interview once the logging period ends, walking through the participant's own entries together. Usually where the real insight surfaces, turning raw logs into an explanation of the pattern.
Multi-Cohort Longitudinal Studies
The same diary protocol run across several distinct groups, or repeated at multiple stages of a longer journey. Reveals what is consistent across a population and what varies by segment or stage.
Onboarding & Adoption Diaries
Track the first days or weeks of using a new product, tool, or service, from initial impressions through to whether the habit sticks. Surfaces the drop-off points a single post-launch survey would miss entirely.
When to choose a diary study
The right method when something has to be caught as it happens, not reconstructed afterwards
Choose a diary study when:
The behaviour is infrequent or unpredictable. If something happens every few days on no fixed schedule, an interview only ever catches a description of it. A diary can be in place when it actually occurs.
You need to see change over time. Onboarding, habit formation, a symptom or a treatment that evolves week to week: anything that is really "how does this change" needs multiple time points from the same person, not one interview reconstructing the arc afterwards.
The moments are private. Some behaviour happens somewhere a researcher can never be present, and some of it people would rather write down alone than say out loud in a session.
The journey spans days or weeks. A multi-stage application, a course of treatment, an extended purchase decision: anything with a beginning, middle and end longer than an hour benefits from a record made at each stage.
Diary studies work well alongside:
An opening interview. Scopes the territory and shapes the diary prompts so they ask about the right things from day one, rather than guessing.
A closing interview. Turns the raw entries into an explanation, walking through specific logs with the participant and asking why things happened the way they did.
Contextual inquiry. Use the diary to find the episodes worth observing in person, then go into the field for those specific moments. See our guide to contextual inquiry for how the two combine.
Usability testing. A diary can surface the friction that shows up days after first use, well after a single moderated session would have ended.
How we run a diary study
Careful design upfront, active management through the logging period, and analysis that turns entries into findings
Study design and prompts
Clear research questions first, then a prompt structure and cadence, scheduled, event-contingent, or a hybrid of both, built to answer them without becoming a chore.
Recruitment and briefing
Participants recruited and screened for the behaviour you need to track, then briefed clearly on what to log, how, and why it matters, so entries start strong from day one.
Format selection
Text, photo, voice, or a mix, chosen for what the research question needs, weighed honestly against the completion rate each format actually gets over a multi-week study.
Reminder and compliance management
Active monitoring through the logging period. Nudges that feel like reminders rather than nagging, and early flags if a participant is falling behind so we can re-engage before the study loses them.
Fair, honest participant payment
Diary studies ask more of someone's time and attention than a single session, spread out in a way that disrupts their day more than an hour-long interview. We pay for that ongoing commitment, not a one-off rate.
Closing interviews
A short conversation with each participant once logging ends, walking through their own entries together. Usually where the pattern turns into an explanation of why it happened.
Rigorous analysis
A coding scheme planned before fieldwork starts, not after the entries land, so the volume a diary study generates turns into themes rather than an unread backlog.
Rich reporting
Findings built from the timeline itself: verbatim entries, patterns across participants, and clear implications for design, service, or policy. Not just what people logged, but what it means.
Where diary studies work well
Any question where behaviour unfolds over time, rather than in a single sitting
Diary study pricing
Transparent pricing for longitudinal research that captures the real shape of behaviour, not a summary of it
Focused Study
Diary Study
1–2 weeks of logging with 8–10 participants using a single format. Good for a focused question about a specific behaviour or a short adoption window.
- 8–10 participants
- 1–2 week logging period
- Recruitment and screening
- Reminder and compliance management
- Closing interviews
- Findings report
- 5–6 week delivery
Full Programme
Diary Study Programme
3–4 weeks of logging with 12–15 participants, richer formats where useful, and a full round of closing interviews. Our most common diary study scope.
- 12–15 participants
- 3–4 week logging period
- Scheduled and event-contingent prompts
- Text, photo, or voice formats
- Active mid-study compliance management
- Closing interviews with every participant
- Comprehensive findings report
- 7–9 week delivery
Large Scale
Extended & Multi-Cohort Study
6–8 weeks of logging, or the same protocol run across multiple cohorts or journey stages. For organisations tracking adoption, treatment, or behaviour change at scale.
- Multiple cohorts or journey stages
- 6–8 week logging period, or staged waves
- Bespoke tooling or app-based diary where needed
- Cross-cohort comparative analysis
- Full interview round per cohort
- Comprehensive reporting with implications by segment
- 10–16 week programmes
All packages include: Study design, participant recruitment and incentives, reminder and compliance management through the logging period, closing interviews, thematic analysis, and a written findings report.
Participant payment: Diary studies ask more of participants' time than a single session, spread across days or weeks. Members of our own panel are paid up to £125 for a diary study, reflected in the packages above.
Specialist or clinical populations: Studies involving patients, rare conditions, or professional samples typically add 20–30% to base pricing due to recruitment complexity and any governance requirements.
Add-ons: Dedicated diary app build or licensing (quoted per study), an additional interview round (£3,500), synthesis workshop with your team (£2,000), persona or journey map outputs (£2,500–£3,000).
Common questions
What is a diary study?
A diary study asks participants to record something, a moment, a task, a feeling, a decision, at or near the time it happens, over an agreed period of days or weeks. Entries can be short text notes, photos, voice memos, or ratings. It captures behaviour as it unfolds rather than as someone recalls it afterwards. See our full guide to diary studies for more detail.
How is a diary study different from an interview?
An interview relies on someone recalling a stretch of experience in a single conversation, which works well for opinions but poorly for anything time-dependent, infrequent, or easily forgotten. A diary study captures the moment itself, logged close to when it happened, before memory has had the chance to tidy it up.
What format should participants use to log entries?
It depends on what you need to learn. Short text prompts get the highest completion rates over several weeks. Photo diaries suit anything visual. Voice notes capture tone and frustration that text flattens out. We help you choose the lightest format that still answers your research question, since richer formats get better data per entry at the cost of a lower completion rate.
How much does a diary study cost?
Projects start from £6,500 for a focused one to two week study with 8–10 participants. Larger programmes with richer formats, longer logging periods, or multiple cohorts are quoted based on scope. Every package includes recruitment, participant incentives, reminder management, closing interviews, and a findings report.
How long does a diary study take, start to finish?
A focused study typically takes five to seven weeks from brief to findings: one to two weeks to design and recruit, one to four weeks of logging depending on scope, then closing interviews and analysis. Longer logging periods or multiple cohorts extend the timeline accordingly.
We fully recognise the effort your team invested in recruitment, moderation, and analysis, and we genuinely appreciate the quality of the discussions and reporting.
- Usability problems in an insulin device surfaced before manufacturing locked anything in, with human factors evidence supporting the regulatory submission.
- An NHS patient portal team got a prioritised, evidenced list of adoption barriers, and the highest-leverage fix wasn't the one they expected.
- Patient involvement changed a trial's primary endpoint before the protocol was finalised, cited by the ethics committee as a model for evidencing PPIE.
Trusted PPI and PPIE delivery partner to the NIHR HealthTech Research Centre in Accelerated Surgical Care.
Need to track something over days or weeks?
Tell us what you're trying to understand and over what period. We will help you scope the right format, cadence, and sample for your diary study. From £6,500.
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