The balance stabilising benefit of social touch: influence of an individual’s age and the partner’s relative body characteristics

Interpersonal touch (IPT) is a successful strategy to support the stability of and individual’s body balance during a multitude of activities in daily life, including physical education and therapy. Despite common practice, however, the influence of an individual’s anthropometry and other personal characteristics, such as age, balancing skills, motor experience, and sex as well as interindividual differences in these characteristics between interaction partners on the balance stabilising benefit of social touch is unknown. We assessed an individual’s balance stability and change due to IPT provision during single-legged stance in 72 pairs (age range 4 to 63 years) under four sensory conditions: with or without vision in combination with IPT or without. Two participant subgroups were created: one of more vulnerable with low stability and one of more stable, mature participants. Best fitting multiple linear regression models, including moderating variables, for explaining the benefit of IPT in each visual condition indicated that without vision, an individual’s benefit of IPT was determined by their balancing skill and the partner-related difference in balancing skill but not by any other factors or partner-related differences. Especially vulnerable individuals improved considerably with IPT when vision was unavailable. With vision complementing IPT, however, an individual’s age-dependent motor developmental potential became an additional moderating factor. These findings indicate that the extent to which IPT is benefitting mutual balance stabilisation does not depend on biomechanical factors. Instead, the IPT benefit emerges as a product of both partners’ sensorimotor capabilities moderated by a person’s motor developmental potential when visual feedback could be utilised. We discuss a theoretical framework that accounts for the observed dependencies of the effect of haptic social support on balance control. Significance Statement This work contributes to a better understanding of the factors influencing the benefit of interpersonal touch for balance stabilization across a wide age range from children to senior adults. It is the first work that investigates the role of both individual factors and relative differences between interaction partners on the amount of benefit of IPT and takes moderating factors such as age-related motor developmental potential, sex, and body mass index into account. Future studies can build on this work when selecting or simulating an optimal partner, especially for individuals with postural instability, for example due to age or sensorimotor deficits.