The effect of pleasant touch on nose skin temperature, heart rate and heart rate variability: preliminary results in a male laboratory rhesus monkey

Human and animal studies emphasize the importance of affiliative touch among conspecifics, both from the behavioral and physiological perspectives. Among non-human primates, allogrooming, and in particular the pleasant sweeping motion occurring during it, could be considered analogous to human social affiliative touch. Despite the evidences of the effects of affiliative touch in terms of heart rate (HR) and heart rate variability (HRV), both in humans and non-human primates, the physiological consequences have never been investigated in respect to the body temperature changes through infrared thermography (IRT). The aim of the present study was to investigate for the first time in a male rhesus monkey, the physiological effects of sweeping the back at different speeds in terms of nose skin temperature changes, and to explore the possible relationship with the HR and HRV. The preliminary results underline that sweeping the back at a speed of 5–10 cm/sec determined an increment of the nose skin temperature and HRV, together with a decrement of the HR. These preliminary data represent the first evidence of the body temperature changes manifesting during affiliative touch at the speed of 5–10 cm/sec in non-human primates and the existence of a possible relationship among the body temperature, HR and HRV. This study represents an important starting point in order to investigate the affiliative pleasant social touch by means of non-invasive techniques ( e.g. the IRT), and to deeply examine the correlation between body temperature and cardiac changes, both in humans and non-human primates.