The thermoception task: a thermal imaging-based procedure for measuring awareness of changes in peripheral body temperature

Abstract

Although thermal body signals provide crucial information about the state of an organism and changes in body temperature may be a sign of affective states (e.g., stress, pain, sexual arousal), research on thermal awareness is limited. Here we developed a task measuring awareness of changes in peripheral body temperature (thermal interoception) and compared it to the classical heartbeat counting task (cardiac interoception). With an infrared light bulb we delivered stimuli of different temperature intensities to the right hand of 31 healthy participants. Thermal interoceptive accuracy, i.e., the difference between participants' real and perceived change in hand temperature, showed good interindividual variability. We found that thermal interoception did not correlate with (and was generally higher than) cardiac interoception, suggesting that different interceptive channels provide separate contributions to awareness of bodily states. Moreover, the results hint at the great salience of thermal signals and the need for thermoregulation in day-to-day life. Finally, thermal interoceptive accuracy was associated with self-reported awareness of body temperature changes and with the ability to regulate distress by focusing on body sensations. Our task has the potential to significantly increase current knowledge about the role of interoception in cognition and behavior, particularly in social and emotional contexts.NEW & NOTEWORTHY We developed a novel task measuring awareness of changes in peripheral body temperature (i.e., thermal interoception). To avoid tactile confounds present in existing thermoceptive tasks, we used an infrared light bulb to deliver stimuli of different temperature intensities to the hand of participants and asked them to judge the perceived change in their hand temperature. Performance in the task showed good interindividual variability, did not correlate with cardiac interoceptive tasks, and was associated with self-reported thermosensitivity.

Keywords: body temperature; interoception; thermosensation.

Graphical abstract

Figure 1.

Experimental setup and design. A: the thermoception task setup. Participants are seated at a desk with a rest for their right hand. On their right is a thermostatic water bath, and on their left are a screen and a mouse for instructions and response collection. An infrared light bulb is attached to the desk at a 15-cm distance from the hand. A shield covers the light bulb from view, to avoid response bias due to visual cues. A thermal camera is used to record real changes in hand temperature during the task. B: illustration of a typical trial of the thermoception task. The task consists of 15 trials, 3 for each temperature intensity (0%, 25%, 50%, 75%, 100%). In each trial 1) the participants insert their right hand for 20 s in the thermostatic water bath set at 31.5°C; 2) participants dry their hand, place it on the stand, and receive the 20-s thermal stimulation, delimited by 2 acoustic tones; and 3) participants report the perceived change in temperature from before to after the stimulation on a visuo-analog scale (VAS) ranging from 0 = “Not at all” to 100 = “Very much.”

Figure 2.

Thermal images of a representative participant’s hand. Thermal images were recorded via the thermal camera FLIR A655sc and FLIR Research IR Max software. The images were taken at baseline (2 s before stimulation) and at the end of the 20-s stimulation for each of the 5 intensity conditions (0%, 25%, 50%, 75%, 100%).

Figure 3.

Box plots displaying differences in real and perceived change in hand temperature and interoceptive accuracy based on stimulation intensity. Values for each stimulation intensity are reported (0%, 25%, 50%, 75% and 100%). A represents differences in real change in hand temperature from before to after the stimulation, recorded by a thermal camera in °C. B shows differences in average perceived hand temperature [average of visuo-analog scale (VAS) scores]. C shows differences in thermal interoceptive accuracy. *P < 0.001.

Figure 4.

Rain cloud plots displaying the distribution of raw data, box plots, and split violin plots for thermal and cardiac interoception (accuracy and awareness scores). Values closer to 100 indicate higher scores. *Significant difference in scores at P < 0.001.

Figure 5.

Linear relationship between thermal interoceptive accuracy and self-reported thermosensitivity. Thermal interoceptive accuracy is positively predicted by scores in Heat-Induced Warming (left) and negatively predicted by Heat Perception (right) in the Experienced Temperature Sensitivity And Regulation Scale (ETSRS). *Significant slope at P ≤ 0.01.

Figure 6.

Linear relationship between thermal interoceptive accuracy and self-reported interoceptive sensibility. Self-Regulation [Multidimensional Assessment of Interoceptive Awareness (MAIA-2)] positively predicted thermal interoceptive accuracy. *Significant slope at P < 0.05.