TY - JOUR T1 - Rethinking pain threshold as a zone of uncertainty JF - bioRxiv DO - 10.1101/521302 SP - 521302 AU - Victoria J Madden AU - Peter R Kamerman AU - Mark J Catley AU - Valeria Bellan AU - Leslie N Russek AU - Danny Camfferman AU - G Lorimer Moseley Y1 - 2019/01/01 UR - http://biorxiv.org/content/early/2019/01/17/521302.abstract N2 - The pain threshold is traditionally conceptualised as a boundary that lies between painful and non-painful events, suggesting a reasonably stable relationship between stimulus and response. In two experiments, participants received laser stimuli of various intensities and rated each stimulus on the Sensation and Pain Rating Scale (SPARS), which includes ranges for rating painful and non-painful events and clearly defines the presumed boundary between them. In the second experiment, participants also provided ratings on the conventional 0-100 Numerical Rating Scale for pain (NRS) and a new rating scale for non-painful events. The SPARS has a curvilinear stimulus-response relationship, reflecting that several different intensities may be rated as painful and non-painful in different trials. Here, we used the binomial test to determine the width of this ‘zone of uncertainty’ about painfulness using ratings on the SPARS and the comparator scales, and data visualisation to assess whether trial-to-trial change in stimulus intensity influences ratings. We found that the width of the zone of uncertainty varied between individuals and was wide at the group level on both the SPARS and the NRS, but narrow on the scale for non-painful events. These findings have important implications for experiment design, sample sizes and clinical phenotyping procedures. ER -