What do ‘peripersonal space measures’ really reflect? The action field perspective

The magnitude of a large number of behavioural and neurophysiological measures depends on the proximity between an individual and environmental objects. This relationship has led to the concept of peripersonal space (PPS). Here we argue that the proximity-dependence of such PPS measures could arise as a result of calculating the relevance of actions that aim to create or avoid contact with objects in the world. This perspective, supported by the interactive behaviour framework of systems-level brain function, allows us to describe PPS as a set of continuous fields reflecting contact-related action relevance. The action relevance perspective gets rid of incorrect notions about PPS, such as it being a single in-or-out zone that mainly reflects the spatial distance between objects and the body. This reconceptualization incorporates PPS into mainstream theories of action selection and behaviour. Furthermore, the formal comparison of this framework to others shows that contact-action value allows for a more complete description of PPS measures than proximity coding, impact prediction, and multisensory integration do, while simultaneously explaining the relationship between those concepts and PPS measures.