Self-reports of behaviors and attitudes are strongly influenced by features of the research instrument, including question wording, format, and context. Recent research has addressed the underlying cognitive and communicative processes, which are systematic and increasingly well- understood. I review what has been learned, focusing on issues of question comprehension, behavioral frequency reports, and the emergence of context effects in attitude measurement. The accumulating knowledge about the processes underlying self-reports promises to improve questionnaire design and data quality.

Self-reports are a primary source of data in psychology and the social sciences. From laboratory experiments to public opinion surveys, researchers rely on the answers that research participants provide to learn about individuals' thoughts, feelings, and behaviors and to monitor societal trends, from the nation's unemployment rate to the development of crime. Unfortunately, self-reports are a fallible source of data, and minor changes in question wording, question format, or question context can result in major changes in the obtained results, as a few examples may illustrate:

• When asked what they consider “the most important thing for children to prepare them for life,” 61.5% of a representative sample chose the alternative “To think for themselves” when this alternative was offered on a list. Yet, only 4.6% volunteered an answer that could be assigned to this category when no list was presented (Schuman & Presser, 1981).
• When asked how successful they have been in life, 34% of a representative sample reported high success when the numeric values of the rating scale ranged from −5 to 5, whereas only 13% did so when the numeric values ranged from 0 to 10...