Limitations and biases associated with self-report in general. Despite the importance of self-reports, some important general limitations to the methodology do exist. Participants are usually quite confident in their own ability to recall (Fienberg, Loftus, & Tanur, 1985; Read, Vokey, & Hammersley, 1990), yet a growing body of empirical evidence indicates that retrospective self-reports are susceptible to numerous errors. Research in the field of autobiographical memory suggests that the magnitude of retrospective reporting errors is significant, and can threaten the validity of the information obtained (e.g., Jobe & Mingay, 1991). Autobiographical memory refers to both specific memory of personal episodes and generic knowledge about the self (e.g., Robinson & Swanson, 1990). When recalling self-relevant information, individuals may reproduce a particular incident relatively directly (episodic memory), or reconstruct this information based on more generic views of the self (semantic memory).
The recall of information is also affected by many external factors, such as time since frequency, the event’s last occurrence, and emotions associated with the event. Recent, low frequency, emotionally laden incidents are more easily retained (White, 1989) compared to other incidents that quickly fade and become hard to recall (Engle & Lumpkin, 1992). Thus, one’s annual mammogram from last month would be more easily retained than one’s exercise behavior the previous week. Memory about the source of the information (e.g., when and/or where the incident took place) is also often confused, because specific time and location indicators are lost as similar incidents get integrated into more generic knowledge (Means, Mingay, Nigam, & Zarrow, 1988).
Self-reports are also subject to a range of biases, such as poor memory or inability to accurately summarize past experiences (e.g., Engle & Lumpkin, 1992), current states (e.g., mood; Jobe & Mingay, 1991), frequency of events (Blair & Burton, 1987; Cummings, Nevitt, & Kidd, 1988; Smith, Jobe, & Mingay, 1991), and temporal information (Larsen & Thompson, 1995). In the development of cancer-related measures, it might be preferred to focus on assessments of more recent versus distant past events or experiences. Similarly, obtaining reports of current states rather than past states may be more accurate. When asking participants or patients about the frequency of events, experiences, or states (e.g., "How often have you…?";) researchers should consider providing appropriate recall cues, clearly delivering the questions, and structuring interviews to probe for confusion on the part of respondents. It is also desirable to emphasize to respondents the importance of correct rather than normative responding, and to provide sufficient time and systematic strategies to rely on elaborative introspection rather than recall heuristics (that are more prone to bias).
Aside from cognitive errors arising from memory and recall strategies, there are motivational factors responsible for volitional misrepresentations. Researchers and clinicians should consider that patients often want to present themselves in a favorable manner (a social desirability bias), and that this motivation might affect the validity of self-reports. The effects of social desirability are especially pronounced when answering sensitive topics (e.g., cancer patients who continue to smoke cigarettes, patients who are not taking their medications; e.g., Smith, 1992) or when self-reports are obtained in a public (as oppose to private and/or confidential) context (e.g., Rasinski, Baldwin, Willis & Jobe, 1994). Secondary gain is another source of volitional misrepresentations. Secondary gain refers to external and incidental advantages derived from behaviors and/or illness (e.g., rest, gifts, personal attention, release from responsibility, disability benefits). In short, those who can gain benefits by misrepresenting their state of affairs may willfully choose to do so. Social stigma is associated with severe social disapproval, and thus people may choose to avoid discussing behaviors or illnesses that are stigmatized out of fear that the information may be disclosed (Jones & Forrest, 1992). It is vital to provide and emphasize confidentiality, and to boost motivation, in order to obtain honest and open responses under these circumstances.