In psychology, recall bias (or reporting bias) is a type of systematic bias which occurs when the way a survey respondent answers a question is affected not just by the correct answer, but also by the respondent's memory. http://web.cancernutritioninfo.com/glossary.cfm?id=21 http://www.gulflink.osd.mil/library/randrep/pesticides_survey/mr1018.12.appd.html This can affect the results of the survey. As a hypothetical example, suppose that a survey in 2005 asked respondents whether they believed that O.J. Simpson had killed his wife.