Academic journal article Attention, Perception and Psychophysics

Grab It! Biased Attention in Functional Hand and Tool Space

Academic journal article Attention, Perception and Psychophysics

Grab It! Biased Attention in Functional Hand and Tool Space

Article excerpt

This study explored whether functional properties of the hand and tools influence the allocation of spatial attention. In four experiments that used a visual-orienting paradigm with predictable lateral cues, hands or tools were placed near potential target locations. Results showed that targets appearing in the hand's grasping space (i.e., near the palm) and the rake's raking space (i.e., near the prongs) produced faster responses than did targets appearing to the back of the hand, to the back of the rake, or near the forearm. Validity effects were found regardless of condition in all experiments, but they did not interact with the target-in-grasping/raking-space bias. Thus, the topology of the facilitated space around the hand is, in part, defined by the hand's grasping function and can be flexibly extended by functional experience using a tool. These findings are consistent with the operation of bimodal neurons, and this embodied component is incorporated into a neurally based model of spatial attention.

Humans have evolved to perform functional and adaptive actions in the world. We must respond quickly and effectively when an enemy throws a rock or when a friend tosses an apple at us. In these situations, the current location of our limbs-and especially our hands-influences the speed and success with which we can either knock the rock away or grab the apple. These common examples emphasize the dynamic nature of the environment and the need for our spatial attention system to effectively coordinate visual and bodily information. Thus, visual spatial attention should be influenced by the current position of the hand and the specific functions it performs.

Spatial attention refers to the cognitive process through which certain visual stimuli are selected to the exclusion of other stimuli on the basis of their spatial location (e.g., Vecera & Rizzo, 2003). One of the primary functions of spatial attention is to select objects and locations in space that are functionally relevant to what we are doing now or are about to do (Tipper, 2004). Spatial attention may amplify signals associated with salient regions of space and, thereby, improve perceptual processing (Braun, Koch, & Davis, 2001; Pashler, 1998; Posner & Cohen, 1984). Attention can be controlled in different ways. It can be directed from bottom-up inputs such as visual cues, and it can be directed on the basis of top-down sources such as motivation and goals. It may also be directed on the basis of inputs from the body. The current orientation of our bodies and, specifically, the positions of our hands change the salience of space by providing anchors or references for upcoming actions. However, few studies have examined how the actions of our hands and functional capabilities affect the distribution of spatial attention. In this article, we argue that the functional capabilities of our hands and our functional experiences with tools facilitate processing in the space relevant for upcoming actions.

We propose that theories of attention must include an embodied component that addresses how our bodies help shape the distribution of attention in space and how visual events are processed as a result (Reed, Garza, & Roberts, 2007; Reed, Grubb, & Steele, 2006). The current configuration of our body parts constrains our actions at any moment. As a result, body part location should influence where spatial attention is allocated across visual space. Several studies in neurologically intact populations have documented that attention and lateralized visual target detection are biased by trunk orientation both when one is standing and when one is walking (Grubb & Reed, 2002; Grubb, Reed, Bate, Garza, & Roberts, 2008; Hasselbach- Heitzeg & Reuter-Lorenz, 2002).

In addition to the trunk, hand location also affects processing in regions of space in which functional actions can be performed-namely, peripersonal space. Researchers have distinguished among space on the body (personal space), space near the body (peripersonal), and space far from the body (extrapersonal) (e. …

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