Abstract
Individuals constantly modulate their exploratory movements and adapt their internal hypotheses to incoming sensory information to achieve a thorough and realistic percept. Perception depends on the exploratory movements as well as influencing them. While this seems to be common sense, scientifically we know very little about the temporal dynamics during haptic exploration. To address this, we investigated the exploratory force modulations of two groups of healthy young adults during the exploration of grated surfaces with differing detection difficulty during successive (n = 20) and random stimulus presentation (n = 20). Results showed that exploratory force depended on stimulus properties and increased with increasing detection difficulty. Both experiments yielded the same direction of results with slightly smaller effects in the random stimulus presentation group. Across exploration time average fingertip force also increased. The biggest increase occurred systematically at the beginning (within the first 40 percent) of exploration time per stimulus indicating that most critical information is received during the initial contact phase and is directly transformed into the exploration procedure and force application. Furthermore, video-analyses and comparisons to our high temporal resolution data revealed strong dynamic changes in pressure application during test stimulus exploration with differences in the force dynamics and exploration strategies of simple and difficult stimuli.
Highlights
The detailed analysis of interactions between sensory and motor information processing is essential for the understanding of haptic perception
Based on the findings reported above we expect both exploration time and fingertip force to increase with increasing detection difficulty both during successive and random stimulus presentation
We found that mean fingertip force as well as temporal force modulations were strongly influenced by stimulus properties
Summary
The detailed analysis of interactions between sensory and motor information processing is essential for the understanding of haptic perception. Active and goal oriented exploration of objects and surfaces is accompanied by a multitude of physiological, motor and cognitive processes. For these processes to occur it is fundamentally important that a direct physical contact between the organism and the material structure of the object is established. Self-this active initiation of physical contact is the prerequisite for all subsequently occurring manipulations and control processes. During haptic perception of objects and surfaces, organisms constantly modulate their movements and adapt their internal hypotheses to the incoming sensory.
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