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Object -oriented behavior grasping from a perception/action perspective
Object-oriented behavior requires the fine interplay between perception and action. Two visuomotor cortical channels are typically implicated in grasping. One is described as specifically sensitive to extrinsic object parameters (e.g., location). The other is described as specifically sensitive to intrinsic object parameters (e.g., shape). According to Jeannerod (1981), the first, dorsal, channel directs the arm transport component of a grasp, while the second, ventral, channel directs the object manipulation component of a grasp.^ The role of both types of object information in planning a grasp is examined. Specifically, questions directed at the degree of planning by each component, their independence from one another, as well as their mode of planning (serial vs. parallel) are addressed. Two experiments employed a precueing paradigm to manipulate the type of information available prior to movement onset. Variables examined were the location of an object (left/right), its shape (sphere/dowel), as well as its distance from the hand. The primary measure of interest was reaction time to a "go" signal. The kinematics of the ensuing movements were also analyzed.^ Sizable reaction time costs were found when either type of information was precued ambiguously or incorrectly. Such costs illustrate that both extrinsic and intrinsic object parameters are critical for planning a grasp, supporting the active participation of both components in planning. The overall pattern of reaction time results implies that the arm transport channel is responsible for 'sketching out' an overall plan of action upon which the plan for object manipulation 'rides.' The absence of an interaction between extrinsic and intrinsic parameters, furthermore, suggests that the two channels are functionally independent. The additive effects of extrinsic and intrinsic parameters, finally, is evidence for a serial mode of planning by the two channels.^ The kinematics of the movements support findings from the literature, and suggest that movements are not time-scaled variations of a prototypical movement. They also reveal that the arm transport component of the movement is affected by both extrinsic and intrinsic object properties; the object manipulation component, on the other hand, appears only sensitive to intrinsic object properties. ^
Psychology, Behavioral|Psychology, Experimental
Loukia D Loukopoulos,
"Object -oriented behavior grasping from a perception/action perspective"
(January 1, 1997).
Doctoral Dissertations Available from Proquest.