Gather a group of participants together who share the characteristic you are looking to study.
Develop a questionnaire that explores the reasoning behind the group's behaviors. Ask them to describe emotions, feelings and the pros and cons of certain decisions.
Pass the questionnaire to each participant and ask her to fill it out. Compile the feedback and begin to analyze it, looking for common patterns and traits in the responses.
Conduct a focus group with the participants. This serves as an open discussion that is guided by the common traits and patterns that you've extracted from responses to the questionnaire.
Record audio of the focus group and analyze it later, looking for further insights into what drives the patterns that you have noticed.