Sensory and predictive signals in human haptic exploration

Human haptic perception is inherently active. When humans aim to perceive their environment by touch, for example when they aim to haptically perceive the softness of an object, they first have to appropriately explore the object with the fingers. It is this exploratory movement that generates the relevant sensory information. Often a single movement seems not sufficient, but humans repeatedly explore the object before they deliver a judgment. In several experiments we investigated how humans utilize active movement control in touch. Our results show how people fine-tune their exploratory movements in order to improve the gathering of sensory information, how they use repeated exploratory movements to gather sufficient information and how an interplay of closed-loop sensorimotor processes and implicit predictive open-loop processes - based on diverse classes of prior information - determines the control of exploratory movement. Overall, we conclude that human haptic perception is based on efficient processes, in that exploratory movements are optimized in different ways.