Wisen's notes

# Perception of pain can be affected by expectation

It's easy to think that pain is all bottom-up processing (Perception combines bottom-up and top-down processing), but there are evidence that the perception of pain can be altered by what we expect and what we pay attention to.

Parents may sometime notice that their young children would only start to cry when they see a new bruise, even if it's been there for a couple of minutes. Parents may think that their children are lying, which could be one possibility, but another likely possibility is for their children to experience pain due to their children's own expectation to feel pain when they see bruises.

The similar effect is happening when a patient is given a placebo, where their expectation that they'll feel better influence their perception of pain.

# References

Goldstein, Cognitive Psychology (p. 61).

Finally, and perhaps you have experienced this yourself, think about the moments you started to feel pain only after you saw (and paid attention to) the wound on the side of your leg.

Goldstein, Cognitive Psychology (p. 61).

Indeed, modern research has shown that pain can be influenced by what a person expects, how the person directs his or her attention, and whether distracting stimuli are present (Wiech, Ploner, & Tracey, 2008). In a hospital study in which surgical patients were told what to expect and were instructed to relax to alleviate their pain, the patients requested fewer painkillers following surgery and were sent home 2.7 days earlier than patients who were not provided with this information. Studies have also shown that a significant proportion of patients with pathological pain get real relief from taking a placebo, a pill that they believe contains painkillers but that, in fact, contains no active ingredients (Finniss & Benedetti, 2005; Weisenberg, 1977, 1999).