The why, who and how of social touch

A growing body of evidence from the behavioural and neural sciences indicates that social touch has a vital role in human development and psychological well-being. Despite some advances, differences in emphasis and approach across disciplines have hampered a comprehensive understanding of touch behaviour in social interactions. In this Review, we synthesize findings from quantitative and qualitative research in psychology and neuroscience to present a cross-disciplinary framework for investigating social touch and interpreting the associated behaviour. This framework elucidates levels of analysis and explanation for the functions, evolution, mechanisms and development of social touch. We highlight three main areas of inquiry, many of which remain under-researched: the purpose of social touch ('why'), the individuals involved in the touch ('who') and the use of social touch in a given situation ('how'). Together, these dimensions can accommodate features of social relationships from the level of the individual to society while also taking into account the influence of intention, motivation and emotion on social touch. We also consider important yet often overlooked factors such as the species' evolutionary history, language and sociocultural variables, as well as biological mechanisms underpinning social touch. Social touch plays a vital part in human development and psychological well-being, but relevant research is often siloed across disciplines. In this Review, Suvilehto and colleagues integrate across areas and approaches to draw conclusions regarding the purpose, participants and use of social touch.