Rob Withagen

The role of feedback information for calibration and attunement in perceiving length by dynamic touch

Two processes have been hypothesized to underlie improvement in perception: attunement and calibration. These processes were examined in a dynamic touch paradigm in which participants were asked to report the lengths of unseen, wielded rods differing in length, diameter, and material. Two experiments addressed whether feedback informs about the need for reattunement and recalibration. Feedback indicating actual length induced both recalibration and reattunement. Recalibration did not occur when feedback indicated only whether 2 rods were of the same length or of different lengths. Such feedback, however, did induce reattunement. These results suggest that attunement and calibration are dissociable processes and that feedback informs which is needed. The observed change in variable use has implications also for research on what mechanical variables underlie length perception by dynamic touch.

The Calibration of Walking Transfers to Crawling: Are Action Systems Calibrated?

Calibration is needed to scale actions appropriately. Earlier studies suggested that calibration transfers to actions that serve the same goal (Rieser, Pick, Ashmead, & Garing, 1995). This experiment further tested this functional hypothesis by asking whether the calibration of walking transfers to crawling. To recalibrate walking, participants walked on a treadmill for 15 min in a virtual environment in which the visual speed was faster than, equal to, or slower than the walking speed. After each of these rearrangement phases, the participants had to walk or crawl to a seen place without vision. The distance locomoted showed that the calibration of walking generalized to crawling, which supports the functional hypothesis. It is suggested that action systems are calibrated.

Transfer of calibration in length perception by dynamic touch

Earlier studies suggested that the calibration of actions is functionally, rather than anatomically, specific; thus, calibration of an action ought to transfer to actions that serve the same goal (Rieser, Pick, Ashmead, & Garing, 1995). In the present study, we investigated whether the calibration of perception also follows a functional organization: If one means of detecting an information variable is recalibrated, are other means of detection recalibrated as well? In two experiments, visual feedback was used to recalibrate perceived length of a rod wielded by the right hand; the recalibration was found to transfer to length perception with the left hand. This implies that calibration in perception is organized functionally rather than anatomically, and supports the general view that calibration applies to functional systems.

Naturalizing Perception Developing the Gibsonian Approach to Perception along Evolutionary Lines

We believe that one of the most important aspects of Gibsons ecological psychology is his attempted naturalization of perception, that is, his attempt to place perception in the context of evolutionary theory. However, the dominant neo-Gibsonian approach to perception has been criticized for being inconsistent with evolutionary theory. We argue that a central tenet of this approach indeed runs counter to evolutionary considerations. Based on an evolutionary analysis of the use of information, we sketch an alternative development of Gibsons pioneering ideas. A truly naturalistic theory of perception, we argue, should recognize both suboptimalities in perception and variation among the members of a population in what informational variables are used. Like other variable organismal features, the use of information is a function of multiple factors. We will compare this naturalistic ecological approach with both Gibsons own perspective and more recent frameworks.

Towards a new ecological conception of perceptual information: Lessons from a developmental systems perspective

Over the last decades or so, empirical studies of perception, action, learning, and development have revealed that participants vary in what variable they detect and often rely on nonspecifying variables. This casts doubt on the Gibsonian conception of information as specification. It is argued that a recent ecological conception of information has solved important problems, but insufficiently explains what determines the object of perception. Drawing on recent work on developmental systems, we sketch the outlines of an alternative conception of perceptual information. It is argued that perceptual information does not reside in the ambient arrays; rather, perceptual information is a relational property of patterns in the array and perceptual processes. What a pattern in the ambient flow informs about depends on the perceiver who uses it. We explore the implications of this alternative conception of information for the ecological approach to perception and action.

The Role of Affordances in the Evolutionary Process Reconsidered A Niche Construction Perspective

Gibson asserted that affordances are the primary objects of perception. Although this assertion is especially attractive when considered in the context of evolutionary theory, the role that affordances play in the evolution of animals’ perceptual and action systems is still unclear. Trying to combine the insights of both Gibson and Darwin, Reed developed a selectionist view in which affordances are conceived as resources that exert selection pressures, giving rise to animals equipped with action systems. Reed’s advocacy of selectionism, however, has been criticized on several grounds, among which is an inconsistency with recent trends in evolutionary thinking. Current developments in evolutionary biology indeed ask for a reconsideration of the role of affordances in the evolution of perceptual and action systems. Adopting a niche construction perspective, we reexamine the role of affordances in the evolutionary process. It is argued that affordances and their utilization, destruction, and creation are central elements in evolutionary dynamics. The implications for ecological psychology and evolutionary theory are explored.

On Ecological Conceptualizations of Perceptual Systems and Action Systems

This article examines Gibson’s concept of perceptual system and Reed’s concept of action system. After discussing several assumptions underlying these concepts, the ontological status of these systems is considered. It is argued that perceptual systems and action systems should be conceptualized neither as parts of an animal’s body nor as softly (temporarily) assembled devices; rather, they are best understood as animals’ abilities to achieve functional relationships, that is, as dispositional properties. This conceptualization entails that these systems are relatively permanent properties of the animal that are causally supported by, though not identical to, anatomical substrates. Further, it entails that it is the animal that perceives and acts, not its perceptual and action systems.

The Pickup of Nonspecifying Variables Does Not Entail Indirect Perception

A number of recent empirical studies revealed the pickup of nonspecifying variables. This raises the question of whether perception is sometimes indirect. In this article this question is addressed and answered in the negative. First, it is argued that empirical studies are likely to reveal that animals also rely on nonspecifying variables. Probably not every meaningful environmental property is specified by an informational variable. Furthermore, from an evolutionary perspective there is reason to believe that animals also attend to nonspecifying variables, even if specifying information exists. Second, it is argued that the pickup of nonspecifying variables does not entail indirect perception. Gibsons (1959, 1966, 1979/1986) conception of perception as a direct epistemic contact with the environment is adopted. It is suggested that this epistemic contact can be thought of as a continuum-the contact can differ in degree. The strength of the contact is determined by the informational variable exploited. In this framework, the animal is in direct epistemic contact with an environmental property, regardless of whether a specifying or nonspecifying variable is exploited.

Information, Perception and Action: A reply to commentators

In response to Milner and Goodales (1995) interpretations of the dorsal and ventral streams and to empirical results on punching of falling balls, Michaels (2000) argued for the acceptance of a certain separation of perception and action. Awareness of properties of the environment, which are important for telling, was tentatively separated from the visual guidance of coordinated movement. Her article was followed by a number of stimulating commentaries; we reply to those commentaries here. We elaborate on certain points and retreat on others but, in general, maintain the utility of the distinction. We argue further for a commitment to ecological principles, rather than to pluralism.

The horizontal worldview: A Wittgensteinian attitude towards scientific psychology

Many scientific psychologists (implicitly) adopt a vertical worldview. This worldview assumes a layered supervening ontology and thereby invites a reductionist stance on explanation. In the present article we direct attention to an alternative attitude towards reality, the horizontal worldview. We draw on Wittgenstein as an example of this alternative attitude. In his later writings Wittgenstein showed his readers how to resist the urge to derive underlying principles about reality by tirelessly reorienting inquiry “sideways,” to the surrounding circumstances that were excluded from consideration. We go on to identify similar horizontal thinking in scientific psychology and demonstrate its merits by discussing Gibson’s approach to visual perception, a Heideggerian approach to skill acquisition, and by discussing psychological traits and the use of concepts. By clarifying the particular surrounding circumstances that a vertical view neglects to consider, a horizontal attitude can render a vertical analysis superfluous.