Purpose: Work at the intersection of psychology and economics has documented that people are often unable to accurately predict how their preferences and feelings will change when they are in a different state. Behavioral economists have labeled this phenomenon “projection bias” in predicting one’s future choice behavior. A person not in pain may have trouble understanding the value of pain-reduction if she were in fact in pain. Similarly, a person in extreme pain may overestimate the value placed on reducing modest amounts of pain. Our study seeks to understand whether these types of projection bias exist. We examined willingness-to-pay for pain relief and its association with pain level before and after spinal injection treatment among persons with lumbar pain.
Method: We conducted face-to-face interviews with persons completing treatment in a pain clinic for lumbar stenosis (N=17). Subjects were 53% male, 63% white, 37% black and the median age was 46. Prior to treatment, subjects were asked their willingness to pay (WTP) to be free of imagined pain rated a 3, 5, 7 and 10. After treatment, subjects were asked their willingness to pay for relief of their remaining post-treatment pain. Based on the imagined pre-treatment pain levels we computed linear extrapolations for pain levels 1-10 and compared responses to WTP at the imagined/extrapolated pain levels to the WTP post-treatment in order to quantify projection bias. We then examined projection bias by pre-treatment pain level, and pre-post change in pain.
Result: Five subjects (29%) had perfect predictions based upon their imagined pain states. Three subjects (18%) had higher than predicted WTP (one of whom had a pain increase). The remaining 9 subjects (53%) all gave answers in line with projection bias (lower than predicted post-treatment WTP). Subjects with pre-treatment pain > 7 had higher projection bias (p=.02) and projection bias was correlated with magnitude of pain reduction (r=.47, p=.05).
Conclusion: We found evidence of projection bias in this pilot. Our findings suggest a need to account for projection bias when using contingent valuation methods to establish the potential benefits of pain-reduction therapies. Projection bias may also be creating an empathy disconnect for doctors and nurses (who are generally in a non-pain state) trying to weigh costs and benefits of different pain-reduction strategies for their pain patients.
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