Academic journal article Attention, Perception and Psychophysics

Negative Hysteresis in the Behavioral Dynamics of the Affordance "Graspable"

Academic journal article Attention, Perception and Psychophysics

Negative Hysteresis in the Behavioral Dynamics of the Affordance "Graspable"

Article excerpt

Published online: 8 March 2013

(Q> Psychonomic Society, Inc. 2013

Abstract One commonly perceives whether a visible object will afford grasping with one hand or with both hands. In experiments in which differently sized objects of a fixed type are presented, the transition from using one of these manual modes to the other depends on the ratio of object size to hand span and on the presentation sequence, with size increasing versus decreasing. Conventional positive hysteresis (i.e., a larger transition ratio for the increasing sequence) can be accommodated by the order parameter dynamics that typify self-organizing systems (Lopresti-Goodman, Turvey, and Frank, Attention, Perception, & Psychophysics 73:1948- 1965, 2011). Here we identified and addressed conditions of unconventional negative hysteresis (i.e., a larger transition ratio for the decreasing sequence). They suggest a second control parameter in the self-organization of affordance perception, one that is seemingly regulated by inhibitory dynamics occurring in the agent-task-environment system. Our experimental results and modeling extend the investigation of affordance perception within dynamical systems theory.

Keywords Affordances · Grasping · Dynamic modeling · Hysteresis

(ProQuest: ... denotes formulae omitted.)

Definitions of affordance and hysteresis

As a first approximation, Gibson's (1979/1986) concept of affordance can be defined as follows: An object affords a given activity for an agent on a specific occasion (or in a specific setting) if and only if the object and the agent are mutually compatible on dimensions of relevance to the activ- ity (Petrusz & Turvey, 2010; Shaw et al. 1982; Turvey & Shaw, 1979). In the present research, the affordance under discussion is "graspable." For a human in reach of a block of wood, the block affords the activity of grasping with one hand if and only if a mutual compatibility of relevance to grasping holds between the agent's dimensions (e.g., hand span) and the object's dimensions (e.g., width).1

When an object does not afford the activity of unimanual grasping, it might still afford the activity of bimanual grasp- ing, or it might afford no manual grasping activity at all. In the research presented here, the notion of occasion or setting refers to a particular "history" of the object-either one of systematic increase in object size, from significantly less to significantly greater than hand size, or one of systematic decrease in object size, from significantly greater to signif- icantly less than hand size. The two "histories" are, equiv- alently, two different initial conditions: either beginning with unimanually graspable objects, or beginning with objects that are either not graspable or are graspable bimanu- ally. Of primary concern in the reported experiment was the dependence of the grasping activity on whether the sequence of object presentation began with an object graspable with one hand or with an object not graspable with one hand.

The standard term for the dependence of a physical system's current activity on its history is hysteresis. The magnetization of a given material, for example, depends not only on the magnetic field to which the material is presently exposed, but also on the magnetic fields to which it has previously been exposed. The dependency is usually of a specific form: For a sequence of increasing and then decreasing field magnitudes, the onset of magnetizing is at a larger field magnitude than the onset of demagnetizing. It has become necessary to refer to this usual historic effect as positive hysteresis because of contemporary (and much less frequent) observations of the reverse-namely, the onset of magnetizing occurring at a smaller magnetic field magni- tude than the onset of demagnetizing, a case of negative hysteresis (see, e.g., Kochereshko et al., 1995). Negative hysteresis has come under investigation in a variety of systems, both physical and biological. …

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