Sensory and affective judgments of skin during inter- and intrapersonal touch
Center for Neurosensory Disorders, School of Dentistry, University of North Carolina at Chapel Hill, 2160 Old Dental Bldg., Chapel Hill, NC 27599-7450, USA. Acta psychologica
(Impact Factor: 2.19).
02/2009; 130(2):115-26. DOI: 10.1016/j.actpsy.2008.10.007
Here we report two experiments that investigated the tactile perception of one's own skin (intrapersonal touch) versus the skin of other individuals (interpersonal touch). In the first experiment, thirteen female participants rated, along four perceptual attributes, the skin of their own palm and volar forearm, then that of several of the other participants. Ratings were made using visual analogue scales for perceived smoothness, softness, stickiness, and pleasantness. One's own skin was rated less pleasant than the skin of others. For both intra- and interpersonal touch, the forearm skin was rated smoother, softer, less sticky and more pleasant than the palmar skin. In the second experiment, ten pairs of female participants rated each other's palm and volar forearm skin, with the skin of the touched individual being assessed before and after the application of skin emollients that alter skin feel. As in the first experiment, the untreated skin of others was rated more pleasant than the participants' own skin, and the forearm versus palm differences were replicated. However, the emollient had generally larger effects on self-assessments than the assessments of others, and the site effect showed greater positive sensory and pleasantness increases for palm versus volar forearm. The disparate results of the two experiments suggest that attention, influenced by the ecological importance of the stimulus, is more important to assessment of touched skin than ownership of the skin or the contribution to self-touch made by the additional receptors in the passively touched skin. In both experiments, the pleasantness of touched skin was associated with the skin's perceived smoothness and softness, with weak trends toward negative associations with its perceived stickiness, consistent with prior research using inanimate surfaces (e.g., textiles and sandpapers).
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- "Ramona  also found that the friction induced vibrations of surface roughness can affect the tactile perception. On the investigation of the tactile sensation during friction contact, some studies reported that soft and smooth materials were regarded as comfortable, those that were stiff, rough, or coarse as uncomfortable   . Cadoret  reported the generally unpleasant sensations associated with manipulation of sticky or greasy surfaces may be due to the unusually strong or weak tangential force signals, which would ultimately interfere with estimating the frictional properties of manipulated object. "
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ABSTRACT: There are many mechanical stimulation receptors and sensory nerve endings in human skin, which are the important tools in tactile perception. It is a complex process for human to perceive objects and friction relative motion plays an important role during this process. When human’s fingertips friction against objects, they will produce compression and tensile mechanical deformation, which can stimulate the mechanical stimulation receptors in fingertip skin to produce corresponding action potentials and impulses signals. The signals which contain object’s physical properties are transmitted to cerebral cortex by nervous system, thus the shape and surface texture of objects are perceived. Thus the friction between the fingertip and object is an important factor to perceive objects. There exist positive connection between friction and tactile perception. However, limited quantitative parameters can be used to evaluate the perception, and they have rarely been studied scientifically. In this paper, the friction perceptions of fingertip skin rubbing against different roughness sandpapers were studied by biofeedback of frictional signals, physiological and psychological responses. An UMT-II tribometer was used to measure tribological parameters of the fingertip, and corresponding physiological response of electroencephalogram (EEG) signals were monitored by using a Physiological Monitoring and Feedback Instrument (NeXus-10) with BioTrace+software. The psychological responses were scored according to the volunteer’s perception during friction tests. The correlation models among the perception of fingertip, friction coefficient and EEG signals were established by applying regression analysis method. Results showed that the friction coefficient, amplitudes of EEG signals and psychological responses increased with the roughness of sandpapers increasing. There existed a significant correlation among the friction perception of different surface roughness, friction coefficient and amplitudes of EEG signals. By using this method, the perception of fingertip skin for different roughness surface during friction can be evaluated quantitatively.
Available from: Rafaela R Campagnoli
- "Although mutual grooming in humans has received much less attention from researchers than in other primates, the assessment of mutual grooming in human dyadic relationships through a scale revealed that allogrooming is quite frequent in humans (Nelson and Geher, 2007). Indeed, caressing another person's skin is fairly pleasant for the toucher (Guest et al., 2009; Morrison et al., 2010). Actively touching something soft seems to be comforting since infancy. "
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ABSTRACT: It is assumed that social bonds in humans have consequences for virtually all aspects of behavior. Social touch-based contact, particularly hand caressing, plays an important role in social bonding. Pre-programmed neural circuits likely support actions (or predispositions to act) toward caressing contacts. We searched for pre-set motor substrates toward caressing by exposing volunteers to bonding cues and having them gently stroke a very soft cloth, a caress-like movement. The bonding cues were pictures with interacting dyads and the control pictures presented non-interacting dyads. We focused on the readiness potential, an electroencephalographic marker of motor preparation that precedes movement execution. The amplitude of the readiness potential preceding the grasping of pleasant emotional-laden stimuli was previously shown to be reduced compared with neutral ones. Fingers flexor electromyography measured action output. The rationale here is that stroking the soft cloth when previously exposed to bonding cues, a compatible context, would result in smaller amplitudes of readiness potentials, as compared to the context with no such cues. Exposure to the bonding pictures increased subjective feelings of sociability and decreased feelings of isolation. Participants who more frequently engage in mutual caress/groom a " significant other " in daily life initiated the motor preparation earlier, reinforcing the caress-like nature of the task. As hypothesized, readiness potentials preceding the caressing of the soft cloth were significantly reduced under exposure to bonding as compared to control pictures. Furthermore, an increased fingers flexor electromyographic activity was identified under exposure to the former as compared to the latter pictures. The facilitatory effects are likely due to the recruitment of pre-set cortical motor repertoires related to caress-like movements, emphasizing the distinctiveness of neural signatures for caress-like movements.
Available from: Jean-Louis Thonnard
- "Indeed, previous studies have shown that certain physical parameters of surfaces, such as topography, roughness, and temperature, may influence the perception of pleasantness. For instance, the subjective sensation of smoothness or roughness has been associated with a pleasant – or unpleasant – perception, respectively, during active – and passive touch . Only a few studies have investigated the link between innocuous thermal sensations and pleasantness perception. "
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ABSTRACT: Tactile explorations with the fingertips provide information regarding the physical properties of surfaces and their relative pleasantness. Previously, we performed an investigation in the active touch domain and linked several surface properties (i.e. frictional force fluctuations and net friction) with their pleasantness levels. The aim of the present study was to investigate physical factors being important for pleasantness perception during passive fingertip stimulation. Specifically we were interested to see whether factors, such as surfaces' topographies or their frictional characteristics could influence pleasantness. Furthermore, we ascertained how the stimulus pleasantness level was impacted by (i) the normal force of stimulus application (FN) and (ii) the stimulus temperature (TS).
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