Start with the decision, not a list of roles
A customer may say, “I chose this product,” even when someone else identified the need, compared alternatives, approved the cost or uses it every day. This is common in households and workplaces, where a single decision can involve people with different priorities. If an interview focuses only on the person who completed the purchase, it may miss the steps that made that purchase possible.
Begin by defining the decision you want to understand. Was it the choice to start looking, the selection of a particular option, or the choice to keep using it? Then ask the participant to walk through what happened, from the first sign of a need to the final decision. Let roles emerge from their account rather than opening with assumptions such as “Who was the decision-maker?”
Ask what each person did
Concrete questions make shared decisions easier to describe. You might ask, “Who first brought up the problem?”, “Who looked at other options?”, “Who needed to agree before you could proceed?” and “Who uses the product now?” Follow up with what the participant saw or heard: a conversation, a comparison someone shared or a request for approval. This helps distinguish direct experience from the participant’s interpretation of another person’s thinking.
Avoid treating involvement as a simple yes-or-no category. One person may set a budget but leave the choice of product to someone else. A frequent user may have little say in the initial purchase but considerable influence over whether it is renewed. The roles may also change when a family’s needs or a team’s responsibilities change.
Decide whose perspective you need
One interview can reveal that other people were involved, but it cannot establish what those people thought. If the research question concerns how an option was evaluated, consider speaking with someone who compared alternatives as well as the purchaser. If it concerns day-to-day usefulness, include a user who did not make the purchase. Choose participants based on the part of the decision you need to understand, rather than trying to interview everyone connected to it.
Separate interviews can give people room to describe disagreement without adjusting their answers in front of a partner or colleague. In some projects, a joint conversation may be useful for hearing how people recall a decision together, but it can also obscure differences in memory or influence. Match the format to the question, and do not pressure a participant to provide another person’s contact details. If you invite someone else, approach them appropriately and seek their own agreement to participate.
Explore disagreements without taking sides
A difference of opinion is often more informative than a tidy account of consensus. Ask when preferences diverged, what each person wanted at that point and what happened next. Neutral prompts such as “How was that resolved?” leave space for a participant to describe compromise, delay or a decision made by one person. Avoid framing one view as an obstacle that had to be overcome.
Be careful with accounts of absent people. “My manager only cared about price” is a participant’s description, not a verified statement of the manager’s priorities. Record it as such. If you later interview the manager, ask about their own experience rather than presenting the earlier account for confirmation. This preserves the distinction between perspectives and reduces the chance that one interview shapes another.
Map the process without flattening it
After the interviews, make a simple timeline of the decision. For each stage, note who the participant said was involved, what action they took and which details come from firsthand experience. Mark gaps explicitly: you may know that an approval was needed without knowing how the approver reached a conclusion. Keep differing accounts side by side rather than forcing them into a single version of events.
Use the map to identify a practical next question. If users struggled after a purchaser selected a product, a study of onboarding may be more useful than another study of purchase preferences. If decisions repeatedly stalled while people compared options, clearer comparison information may be worth testing. The aim is not to assign every person a permanent role; it is to understand where a shared decision happens and whose experience your next decision needs to account for.
