Final answer:
Researchers should use implicit measures to assess attitudes that might not be directly reported due to social desirability bias or internal thought processes that cannot be overtly observed.
Step-by-step explanation:
When researchers are assessing attitudes that people may be unwilling or unable to report, they should make use of implicit measures. These indirect techniques can reveal underlying attitudes that the respondent may not be consciously aware of or may be reluctant to share.
Implicit measures are especially useful when investigating sensitive topics that may evoke social desirability bias or when the subject matter involves internal thought processes that cannot be observed directly. Such approaches contrast with explicit measures like questionnaires that collect quantitative data using closed questions or qualitative data through open-ended questions. In the context of research design, this pertains to data collection methods and the limitations of self-report instruments.