Turning perception on its head: cephalic perception of whole and partial length of a wielded object

Abstract

Flexibility is a fundamental hallmark of perceptual systems. In particular, there is a great deal of flexibility in the ability to perceive properties of occluded objects by effortful or dynamic touch-hefting, wielding, or otherwise manipulating those objects by muscular effort. Perception of length of an occluded wielded object is comparable when that object is wielded by anatomical components that differ in sensitivity, dexterity, and functionality. Moreover, perception of this property is supported by an analogous sensitivity to inertial properties across such components. We investigated the ability to perceive whole and partial length of an object wielded by hand or by head. Experiment 1 found that perception of length by these anatomical components is qualitatively and quantitatively indistinguishable. Experiment 2 found that perception of length is supported by the same specific sensitivity to inertial properties in each case. Experiment 3 found that perception of whole length and partial length are each supported by specific sensitivities to inertial properties and that this is the case for both hand and by head. The results are discussed in the context of the nature of the stimulation patterns and the organization of the haptic system that are likely to support such flexibility in perception.

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

“…Previous research has found evidence of both task-specificity and anatomical independence in perception of properties of wielded objects. In particular, people can direct attention to different exteroceptive properties of wielded object (e.g., object length), and perception of such properties remains invariant across transformations including the anatomical component used to wield the object (see Hajnal, Fonseca, Harrison, et al, 2007a;Wagman et al, 2017). Such flexibility is grounded in sensitivity to task-specific (in this case, exterospecific) components of an invariant mechanical stimulation pattern-the rotational inertia (I) of the person-object system.…”

“…Previous experiments have shown (1) that people can perceive exteroceptive properties of an object wielded with the hand (e.g., whole or partial length of that object), (2) that these abilities generalize to objects wielded by other body parts (including the foot, the torso, and the head), and (3) that perception of such properties is supported by analogous sensitivities to exterospecific components of I across anatomical components (Hajnal, Fonseca, Kinsella-Shaw, et al, 2007b;Palatinus et al, 2011;Wagman et al, 2017).…”

“…A specific property of the personobject system can be perceived when a given object is wielded in different ways, by different effectors, about different joints. For example, people can perceive the length of an object when it is freely wielded or held with minimal movement (Burton & Turvey, 1990;Carello Fitzpatrick, Domaniewicz, Chan, & Turvey, 1992); when it is wielded with the hand about the wrist, the elbow, or the shoulder (Pagano, Fitzpatrick, & Turvey, 1993); or when it is wielded by the hand, foot, torso, or head (Hajnal, Fonseca, Harrison, Kinsella-Shaw, & Carello, 2007a;Palatinus, Carello, & Turvey, 2011;Wagman, Langley, & Higuchi, 2017).…”

“…The invariant nature of I is highlighted not only by the ability to perceive a given property within and across bouts of wielding but also by the ability to perceive a given property by different means of wielding-including cases in which an object is wielded by disparate anatomical components. Studies investigating this latter ability have shown that people can perceive exteroceptive properties of a wielded object such as whole or partial length when an object is wielded by the hand, the torso, the foot, and even the head (Hajnal, Fonseca, Kinsella-Shaw, et al, 2007b;Wagman et al, 2017). Moreover, they can differentiate between two different (but related) exteroceptive properties (e.g., whole length vs. partial length, probe length vs. distance of surface probed) under such circumstances (Hajnal, Fonseca, Kinsella-Shaw, et al, 2007a;Palatinus et al, 2011;Wagman et al, 2017;Wagman & Mason, 2019).…”

“…Doing so provides a relatively strong test of both the task-specificity and the anatomical independence of perception of (proexteroceptive) properties of the person-object system by dynamic or effortful touch (cf. Wagman et al, 2017).…”