Incentive Structures for Diary Studies

Incentive Structures for Diary Studies

A mindful incentive structure can keep diary study participants engaged and responding, without overloading you with low-quality responses.

Compared to other UX research studies, diary studies - especially longer ones - are particularly vulnerable to high participant attrition - when participants stop submitting entries or responding. One of the strongest levers against attrition is the incentive structure itself.

A poorly designed incentive structure can encourage participants to delay submissions, submit low-effort entries, or report only enough to qualify for payment. A thoughtful structure can encourage more consistent, higher-quality reporting over time.

How Incentives Are Different for Diary Studies

Unlike moderated sessions, where participants are typically compensated for their time, diary studies usually compensate participants for their effort. Participants shouldn’t be compensated if they provide too few or no entries, so incentives are often tied to the quantity - and sometimes the quality - of submissions.

When it comes to diary study incentives, cash incentives are the most effective and flexible option. However, there are different levers you can pull to make a cash incentive more or less attractive without really changing how much you compensate participants.

Common Incentive Structures for Diary Studies

There are three common approaches to structuring diary study incentives:

• Paying participants after they complete a minimum number of entries
• Paying participants for each entry
• Using a tiered pay-per-entry structure

Each approach encourages different reporting behaviors and introduces different tradeoffs.

These incentive structures can be blended. For example, a study might have a minimum number of entries to receive payment. However, participants who want to provide more than the study minimum can be compensated further with a pay-per-entry incentive structure. Additionally, you can offer bonus payments to motivate participants to report consistently or provide helpful entries.

Pay for a Minimum Number of Entries

This is the simplest incentive structure to administer. With this approach, all participants receive the same amount, provided they achieve a minimum number of entries.

It’s important that the minimum number of entries you set is realistic and achievable. This will depend on what participants will be reporting. For example, expecting participants to report 10 online purchases in a week may be unrealistic. However, reporting 10 instances of opening and reading an email may be achievable for most people.

The downside to this incentive structure is that participants tend to submit exactly the minimum - there’s little motivation to provide more, especially when entries are long or complex. Additionally, it’s common with this incentive structure that participants submit entries in one burst - usually at the beginning or end of the study, to meet the minimum threshold. As a result, this incentive structure works best for shorter studies and when you’re not so concerned about having entries unevenly distributed throughout the reporting period.

Even with a minimum-threshold structure, it’s useful to understand the approximate value of each entry. If participants withdraw partway through the study, prorated payment can help fairly compensate them for the work they completed.

Pay per Entry

With a pay-per-entry incentive structure, participants earn a set amount per submission. The more they submit, the more they earn. Participants who have more to share are motivated and encouraged to do so. Make sure you have a cap on payable entries to avoid blowing through your budget.

This incentive structure is best where providing entries is effortful. For example, if participants are required to record a video, answer many questions, or provide photographs, paying per entry can make the effort feel worthwhile. How much you pay per entry depends on the effort required to submit it and who is participating in the study. In some of our diary studies with members of the general public in the US, we’ve paid them from as little as a few dollars to as much as $15 per submission.

A pay-per-entry incentive structure brings some downsides and risks. First, the pay-per-entry structure can encourage low-effort or fabricated submissions if participants focus on maximizing compensation rather than accurately reporting experiences. Designing diary-study prompts in ways that make it hard to cheat or make up submissions (e.g., by requiring videos, photographs, or screenshots) can help.

Second, pay-per-entry incentive structures creates administrative work - you’ll need to track what each participant is owed. Automating payments through a reward platform (like Tremendous) can help, but it comes with tradeoffs: participants may receive many small payments that are difficult to track, and you lose the ability to review each submission before approving it.

Tiered Pay-Per-Entry Structures

Tiered pay-per-entry structures assign different incentive amounts to different entries. This approach gives researchers more control over the mix of submissions they receive and is useful when certain types of events are more valuable than others and should be overrepresented in the data.

For example, in a diary study we conducted with homebuyers, participants could log:

• researching online
• speaking with a professional, such as a broker or agent
• visiting a home

If we were interested in encouraging submissions involving professionals or home visits, we could compensate for them at a higher rate than for entries involving online research.

You can also use tiered structures to encourage participants to report regularly throughout the reporting period. In one 4-week study we ran, we offered $15 for the first 4 entries each week. Participants could submit another 4 payable entries in the week, but we offered only $5 for these. This encouraged participants to report every week rather than submit all their entries at the end of the study; however, some participants did save some entries for the next payable reporting period.

The downside of this incentive structure is complexity. Tiered structures require more explanation and more administrative tracking than simpler approaches.

Bonus Payments

You can use bonus payments alongside any of the three incentive structures we’ve discussed. When used appropriately, bonus payments can encourage the consistency, completeness, or responsiveness of reporting.

• Consistency: For example, a study may offer a bonus for submitting at least one entry per week. This encourages participants to contribute throughout the study period rather than submitting entries right at the beginning or end of the reporting period.
• Completeness: Participants can be rewarded for providing a certain number of complete entries (for example, entries that include photographs or videos).
• Responsiveness: If participants must respond to a researcher’s prompt, bonus payments can be awarded for timely responses or replies.

Payment Timing

One last consideration when establishing your incentive structure is payment cadence: when participants are paid can be just as important as how much they are paid, particularly in longer diary studies. Participants can either be paid at the end of the study or in regular payment intervals (for example, weekly).

Paying participants at the end of the study works best for shorter studies. However, for longer studies, a lump-sum payment could cause participants to disengage early if the reward feels distant or uncertain. Breaking up the payment schedule into regular intervals (such as weeks or biweekly) can encourage participants to keep reporting since they get feedback on their contributions.

Multiple payments can create more administrative work than a single end-of-study payment. Additionally, because regular payments are usually tied to reporting goals for a shorter timeframe, some participants may “save up” entries for the next payment period. However, these tradeoffs might be worth it in longer studies, where participant attrition is a real risk.

Communicating Incentive Structures

Finally, for an incentive structure to be effective, it needs to be understood by participants. While reducing complexity can help, communication is key. Ensure that when participants are recruited and onboarded, they are provided with all the details of the incentive structure. Don’t expect participants to remember information you verbally convey!

To avoid confusion or disappointment later, clearly explain in an information sheet how much participants will be compensated, when they will be paid, and what rules an entry must follow to count as valid. If you have quality criteria (i.e., what an entry must look like or contain), include examples, so participants understand your expectations.

Conclusion

Diary-study incentives shape participant behavior, influencing how often participants respond, how consistently they participate, and the kinds of entries they submit. There is no single “best” incentive structure. The most appropriate incentive structure is one that meets your study priorities and yields the types of data you need. When aligned with study goals, incentive structures can improve both participation consistency and data quality.