Bodily pleasure matters: velocity of touch modulates body ownership during the rubber hand illusion

Abstract

The sense of body ownership represents a fundamental aspect of our self-consciousness. Influential experimental paradigms, such as the rubber hand illusion (RHI), in which a seen rubber hand is experienced as part of one's body when one's own unseen hand receives congruent tactile stimulation, have extensively examined the role of exteroceptive, multisensory integration on body ownership. However, remarkably, despite the more general current interest in the nature and role of interoception in emotion and consciousness, no study has investigated how the illusion may be affected by interoceptive bodily signals, such as affective touch. Here, we recruited 52 healthy, adult participants and we investigated for the first time, whether applying slow velocity, light tactile stimuli, known to elicit interoceptive feelings of pleasantness, would influence the illusion more than faster, emotionally-neutral, tactile stimuli. We also examined whether seeing another person's hand vs. a rubber hand would reduce the illusion in slow vs. fast stroking conditions, as interoceptive signals are used to represent one's own body from within and it is unclear how they would be integrated with visual signals from another person's hand. We found that slow velocity touch was perceived as more pleasant and it produced higher levels of subjective embodiment during the RHI compared with fast touch. Moreover, this effect applied irrespective of whether the seen hand was a rubber or a confederate's hand. These findings provide support for the idea that affective touch, and more generally interoception, may have a unique contribution to the sense of body ownership, and by implication to our embodied psychological “self.”

Interoceptive ingredients of body ownership: Affective touch and cardiac awareness in the rubber hand illusion

“…Moreover, in Crucianelli et al (2013; and even more comprehensively in Gentsch et al (2015), we presented data to show that participants rated touch at a velocity of 18cm/s as significantly less pleasant than touch at CT-optimal velocities of 3 cm/s and 9 cm/s. A velocity which is between 3 cm/s and 18 cm/s is thus considered to activate the CT system to an intermediate degree and is thus assumed to be affectively more 'ambiguous'.…”

“…stroking) was administered for three seconds using a soft cosmetic make-up brush (Natural hair Blush Brush, N•7, The Boots Company) at two different velocities: one CT-optimal (3 cm/s) and one not CT-optimal (18 cm/s). Tactile stimulation, of four trials of each velocity in a random order, was alternated between the rectangles drawn on the skin, to minimise habituation (Crucianelli et al, 2013). After each brush stroke, participants verbally rated the pleasantness of the touch using a scale from 0 (not at all pleasant) to 100 (extremely pleasant), which was presented visually.…”

“…In particular, slow, caress-like touch that activates CT afferents optimally can enhance the experience of owning a rubber hand more than fast, emotionally neutral touch that does not cause optimal CT activation (Crucianelli, Metcalf, Fotopoulou & Jenkinson, 2013;Lloyd, Gillis, Lewis, Farrell & Morrison, 2013;van Stralen, van Zandvoort, Hoppenbrouwers, Vissers, Kappelle et al, 2014). Additionally, Lloyd and colleagues (2013) showed that slow/CT-optimal touch enhanced the subjective embodiment of the rubber hand also in the condition when touch was applied to glabrous (non-hairy) skin, known to lack CT afferents (Vallbo, Olausson & Wessberg, 1999).…”

Mentalizing homeostasis: The social origins of interoceptive inference

“…More specifically as regards to the minimal self, a series of recent studies focused on the role of affective touch in the sense of body ownership. Using the RHI paradigm, three independent studies (the first of these being from AF's lab), have now found that slow, caress-like touch of CT-optimal velocities and properties enhanced various subjective and behavioural measures of the RHI more than fast, emotionally-neutral touch (Crucianelli et al, 2013;Lloyd et al, 2013;van Straleen et al, 2014). That is, affective, pleasant touch delivered by another individual appears to be a strong determinant in the process of multisensory integration that determines how a body part is subjectively experienced as mine.…”

A testképtől a testképzavarig

“…Taktilis anhedoniaként [58] emlegetik azt a jelenséget, hogy a gyengéd érintést az anorexiás páciensek kevésbé érzé-kelik, illetve kevesebb kellemességérzést csatolnak hozzá. Az interoceptív deficit befolyásolhatja a test teljes reprezentációját, a testtudatosság alakulását [59]. Bizonyos kutatócsoportok a hangsúlyeltolódást emelik ki, amennyiben az anorexiások a testről érkező vizuális, exteroceptív jelekre jobban támaszkodnak, mint a proprioceptív információkra [60,61], ezáltal sérülékenyebbé, kevésbé rezilienssé válnak a vizuális változásokkal szemben [62,63].…”