title: Perceptual Inference in Chronic Pain: An Investigation Into the Economy of Action Hypothesis.
abstract: OBJECTIVE
  The experience of chronic pain critically alters one's ability to interact with their environment. One fundamental issue that has received little attention, however, is whether chronic pain disrupts how one perceives their environment in the first place. The Economy of Action hypothesis purports that the environment is spatially scaled according to the ability of the observer. Under this hypothesis it has been proposed that the perception of the world is different between those with and without chronic pain. Such a possibility has profound implications for the investigation and treatment of pain. The present investigation tested the application of this hypothesis to a heterogenous chronic pain population.
  
  
  METHODS
  Individuals with chronic pain (36; 27F) and matched pain-free controls were recruited. Each participant was required to judge the distance to a series of target cones, to which they were to subsequently walk. In addition, at each distance, participants used Numerical Rating Scales to indicate their perceived effort and perceived pain associated with the distance presented.
  
  
  RESULTS
  Our findings do not support the Economy of Action hypothesis: there were no significant differences in distance estimates between the chronic pain and pain-free groups (F1,60=0.927; P=0.340). In addition, we found no predictive relationship in the chronic pain group between anticipated pain and estimated distance (F1,154=0.122, P=0.727), nor anticipated effort (1.171, P=0.281) and estimated distance (F1,154=1.171, P=0.281).
  
  
  CONCLUSIONS
  The application of the Economy of Action hypothesis and the notion of spatial perceptual scaling as a means to assess and treat the experience of chronic pain are not supported by the results of this study.
authors.affiliation: *Sansom Institute for Health Research, University of South Australia, Adelaide, SA ¶Neuroscience Research Australia, University of New South Wales, Sydney, NSW, Australia †School of Biomedical Sciences, Centre of Human and Aerospace Physiological Sciences and Pain Research Section, Neuroimaging, Institute of Psychiatry, King's College London §INPUT Pain Management ∥Physiotherapy Department, Guy's and St Thomas' NHS Foundation Trust, London ‡East Surrey Hospital, Surrey and Sussex Healthcare NHS Trust, Redhill, Surrey, UK.
authors.forename: Abby
authors.initials: A
authors.lastname: Tabor
authors.forename: Owen
authors.initials: O
authors.lastname: O'Daly
authors.forename: Robert W
authors.initials: RW
authors.lastname: Gregory
authors.forename: Clair
authors.initials: C
authors.lastname: Jacobs
authors.forename: Warren
authors.initials: W
authors.lastname: Travers
authors.forename: Michael A
authors.initials: MA
authors.lastname: Thacker
authors.forename: Graham Lorimer
authors.initials: GL
authors.lastname: Moseley
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D059031:Anticipation, Psychological; D059350:Chronic Pain / Q000523:psychology*; D005260:Female; D006801:Humans; D007600:Judgment; D008297:Male; D008960:Models, Psychological; D058748:Pain Perception; D011581:Psychological Tests; D011597:Psychomotor Performance; D011601:Psychophysics; D013028:Space Perception; D016138:Walking