AJP-May 2018

'''Chotard, H., Ioannou, S., & Davila-Ross, M. (2018). Infrared thermal imaging: Positive and negative emotions modify the skin temperatures of monkey and ape faces. American Journal of Primatology, 80(5), e22863.'''

Changes in facial temperature have been found to reflect emotional changes in humans. However, the direction of that change (e.g. increase or decrease in temperature for positive emotions) is still not clear. The current study used facial thermal imaging on five primate taxa (three monkey and two ape) while inducing either a positive emotional experience or negative emotional experience in order to determine whether temperature changes in facial regions are related to mood/emotion. Positive experiences included tickling or playing with toys while negative experiences included teasing or food delays. The facial areas measured were the peri-oribital area, nose bridge, nose tip, and upper lip. Based on previous work, the authors hypothesized that positive emotions would decrease facial temperatures while negative emotions would increase facial temperatures. The five species included in the study were: common marmosets, white-throated capuchins, rhesus macaques, bornean gibbons, and western lowland gorillas. During induction of a positive or negative state, facial temperatures were measured using an infrared thermal imaging device (much like a camera that reads facial temperatures). It was found that upper lip temperature increased during negative state induction and nose tip temperature decreased while peri-orbital temperature increased during positive state induction. These findings were (mostly) in agreement with previous human and nonhuman primate studies. However, the opposition seen in facial temperatures for the positive condition was not hypothesized and could have been due to (1) physiological differences and/or (2) the stimuli used to induce the positive and negative states.