Where is your head? Perception of relative position of the head on a wielded object

Abstract

Perception of exteroceptive properties (e.g., object length) by effortful or dynamic touch is both task-specific and anatomically independent. We investigate whether task-specificity and anatomical independence generalize to perception of proexteroceptive properties of the person-object system (i.e., relative position of the body on a wielded object). Moreover, we do so when objects are wielded by a body part that is unlikely to be well practiced in such tasks-the head. Experiment 1 found that participants can perceive the relative location of the head on a wielded object and that such perception is likely supported by task-specific sensitivity to an invariant mechanical stimulation pattern-rotational inertia. Experiment 2 found that participants have at least some ability to differentiate between this property and a related exteroceptive property (i.e., partial length of a wielded object extending to one side of the head). The results are discussed in terms of information for perception by effortful touch and a description of the haptic system as a biotensegrity structure.

Human Exteroception during Object Handling with an Upper Limb Exoskeleton

“…The fact that exteroception was not negatively affected by the presence of the exoskeleton would certainly support this perspective. For instance, previous studies emphasise the flexible versatility of dynamic touch, as the same wielding or probing movements are used to extract different features (partial length, whole length, body position with respect to object) of the same object upon verbal instruction [17,29,30]. The results of the present study take this a step further, as participants appeared competent in attending to the dynamical features of the handheld bar independently of those associated with the exoskeleton.…”

“…The results of the present study take this a step further, as participants appeared competent in attending to the dynamical features of the handheld bar independently of those associated with the exoskeleton. Dynamic touch has also proven to be reliable when using movements across different bodily segments (e.g., lower limbs, trunk, and head [30,31]) demonstrating that this perceptual system is capably assembled across different anatomical structures. Here, the integration of the exoskeleton indeed complexified the architecture of the upper limb effector, although one can only speculate as to whether its (non-physiological) components are co-opted into the smart haptic system.…”