CONDITIONED PREHENSION IN THE PIGEON - KINEMATICS, COORDINATION AND STIMULUS-CONTROL OF THE PECKING RESPONSE

Like human prehensile behavior, the pigeon's ingestive pecking respons e is elicited by visual stimuli conveying information about the locati on and size of the target. This information is used to generate locali zed ingestive pecks whose gapes are amplitude-scaled to seed size, pri or to contact. We employed high-resolution, 'real-time' monitoring of head acceleration, jaw movements and terminal peck location to examine the kinematics, coordination and stimulus control of conditioned peck ing. Conditioning procedures were used to bring pecking under the cont rol of visual targets whose stimulus properties (size, location) were independently varied, while simultaneously monitoring pecking response parameters. Stimulus control of the transport component (peck localiz ation) is extremely precise, even in the absence of a specific localiz ation-dependent reinforcement contingency. Subjects also showed amplit ude-scaling of gape size to the size of a visual target, but over a mo re restricted range than shown to food pellets of comparable sizes. Co mparison of the kinematic profiles of conditioned and ingestive pecks suggests that conditioned pecking is functionally analogous to human ' pointing' rather than 'grasping' behavior. (C) 1998 Elsevier Science B .V. All rights reserved.