Behavioural and neural evidence for self-reinforcing expectancy effects on pain.

Marieke Jepma, Leonie Koban, Johnny van Doorn, Matt Jones, Tor D. Wager.

Behavioural and neural evidence for self-reinforcing expectancy effects on pain.

Nature Human Behaviour, 2018; 2 (11): 838

DOI: 10.1038/s41562-018-0455-8

Link: https://www.nature.com/articles/s41562-018-0455-8

Abstract

Beliefs and expectations often persist despite evidence to the contrary. Here we examine two potential mechanisms underlying such ‘self-reinforcing’ expectancy effects in the pain domain: modulation of perception and biased learning. In two experiments, cues previously associated with symbolic representations of high or low temperatures preceded painful heat. We examined trial-to-trial dynamics in participants’ expected pain, reported pain and brain activity. Subjective and neural pain responses assimilated towards cue-based expectations, and pain responses in turn predicted subsequent expectations, creating a positive dynamic feedback loop. Furthermore, we found evidence for a confirmation bias in learning: higher- and lower-than-expected pain triggered greater expectation updating for high- and low-pain cues, respectively. Individual differences in this bias were reflected in the updating of pain-anticipatory brain activity. Computational modelling provided converging evidence that expectations influence both perception and learning. Together, perceptual assimilation and biased learning promote self-reinforcing expectations, helping to explain why beliefs can be resistant to change.

 

https://sci-hub.tw/https://www.nature.com/articles/s41562-018-0455-8

I think you can get the gist of it by looking at figures 1 and 2, and perhaps reading some of the methods section. The abstract is certainly opaque.

What stands out to me is:
-that they had people record their 'expectation' before writing down the 'experienced' pain. To me, recording the expectation would 'anchor' the rating of reported pain. (See figure 1d)

-What they call NPS (neurological pain signature - which has something to do with fMRI response [see bottom of third page]) starts off showing different responses between high- and low- cue/expectation trials, but this difference seems to go away over time. (See figure 2e.) Presumably the early differences are enough to establish a statistically significant relationship for the whole study.

-Taken together I would say that the relationship between whatever 'pain signature' activity they measured in the brain and expectancy-exacerbated pain rating is fleeting and the difference in pain ratings between high-expected pain trials and low-expected pain trials is an artifact of anchoring.

-I think they just devised a weird game, got a few people to play, and modeled the hell out of the data they collected to support their theory of pain as a 'positive dynamic feedback loop' of expectation and experience.

 

It's one of those articles full of meaningless buzz words beloved by psychologists. Thank goodness the US are finally investing in drug research for pain.