The problem with retrospective reports: intensity

The problem with asking people about the intensity (How painful? How much anxiety? How optimistic? etc.) of a past experience is that intensity is not very well represented in memory. Therefore, when asked about intensity, people must use various mental tricks to reconstruct an answer. The problem is that these reconstructions of past experience bear little resemblance to the past experience as it was experienced.

In a frequently cited study, Redelmeier and Kahneman (1996) asked patients undergoing either colonoscopy or lithotripsy to rate their pain every 60 sec by moving a marker on a computer screen to indicate pain intensity. Then while recovering, within one hour of their procedure, patients were asked to assess their "total amount of pain experienced". Attending physicians were also asked to judge the overall pain experience of each patient. The researchers found that patients' retrospective reports of overall pain experienced were strongly correlated with both peak pain (.64) and end pain (.44) during the final 3 mins of the procedure. They also found that longer procedures were not predictive of recalling greater amount of pain. Even though a longer procedure subjects people to more pain overall, people don't seem to take account of the entire experience in their retrospective reports. Instead, people tend to recall only how bad it got (peak), and how it ended (end).

In addition to the peak/end heuristic, people also resort to various inference strategies. For example, asked about last week's pain, patients often try to contract an answer by noting how much pain they currently have, and then consider whether last week's pain might have been different. If so, the pain report will reflect this anomaly (Ross & Conway, 1986, Ross, 1989; Linton & Melin, 1982), otherwise the current pain will assumed to be representative of last week's pain (Eich et al, 1985) and that's what will be reported. As Schwartz (2010) put it, "... her retrospective report of pain is a function of her current pain and her naive theory about the stability of her pain over time."