Detection of temperature increases in the operating range of warm receptors and of nociceptors.

In healthy subjects the ability to detect small temperature increases in a 'two-alternative forced choice' experiment was tested from different basic temperatures ranging between 36 and 46 degrees C. Detection improved up to an adapting temperature (AT) of 40 degrees C, a further increase of AT into the operating range of nociceptors did not change detection rate. In several experiments the subjects have been asked to rate their confidence after each forced choice on a 6-point scale. From these confidence ratings two measures developed in the context of 'Sensory Decision Theory' have been calculated, one of 'discrimination' and one of 'bias.' A bias towards higher confidence in having detected temperature increases was found to be the clearest sign of transition into the operating range of nociceptors.