Date Published: March 12, 2019
Publisher: Public Library of Science
Author(s): Stephanie Margarete Mueller, Sven Martin, Martin Grunwald, Neil R. Harrison.
Every human being spontaneously touches its eyes, cheeks, chin and mouth manifold every day. These spontaneous facial self-touches (sFST) are elicited with little or no awareness and are distinct from gestures and instrumental acts. Self-touch frequency has been shown to be influenced by negative affect and attention distraction and may be involved in regulating emotion and working memory functions. Yet, even though self-touch research dates back several decades fundamental aspects, like the temporal progression of sFST or the effects of executing hand and touched face area, have not yet been analyzed. For the first time, the present study measured sFST temporal aspects to the millisecond using accelerometers and EMG. Spontaneous self-touch was triggered in sixty participants who completed a delayed memory task of complex haptic relief stimuli while listening to distracting aversive sounds. We found that while both hands were used equally often and with the same overall movement times and contact durations, significant effects occurred for face area in both frequency and contact durations. Ergo the point of touch seems to have some relevance of its own, independently of which hand is used to perform it. The results show that not only frequency but also the point of touch and contact durations are influenced by cognitive and emotional demands. We argue that investigating the fundamental characteristics of sFST will further the understanding of cognitive focusing and attentional mechanisms.
Self-touches, just like posture shifts, object manipulations and mannerisms, are types of self-regulatory movements and have been discussed to be associated with psychological and cognitive processes [1–6]. Self-touch movements are usually performed with one or both hands and involve rubbing, scratching, caressing, or grooming any part of the body’s surface or pieces of clothing or accessories [4,7].
The data for the present study were gathered in an experiment investigating facial self-touch movements (sFST) during a delayed memory task of complex haptic stimuli (sunken reliefs [35–37]. The experimental setting has been successfully used before to induce ST . The study was approved by the Ethics Committee of University of Leipzig Medical Faculty. All participants gave written informed consent.
The data for the present study were gathered in an experiment investigating discrete spontaneous facial self-touches (sFST) during a delayed memory task of complex haptic stimuli (sunken reliefs). For the first time in the history of self-touch research, the present experimental setting was designed to allow objective measurements of the movement and contact times of self-touch processes. Our aim was to investigate the temporal aspects of discrete facial self-touch with focus on the executing hand and touched face area.
Currently, it is much too early for a conclusive theory of self-touch. Despite decades of research we know very little about the physiological fundamentals of this behavior. In the present study we were able to show that cognitive and emotional load play a role in the occurrence of self-touch directed towards the face. But why are sFST directed towards varying face areas? And what triggers these movements? Is it possible that self-touches are only an epiphenomenon of a much more sophisticated neuronal mechanism? It is conceivable that immediately prior to sFST a faint sensory signal may be sent to the skin without any external dermal stimulation. Top-down excitation of dermal receptors causing skin sensations is known through phenomena like contagious itch  or somatic hallucinations . If this is the case it would support the notion that the point of touch is at least as relevant to the self-touch process as the executing hand. And it would welcome an entirely new approach to this omnipresent phenomenon.