Grasping in the pigeon (Columba livid): Stimulus control during conditioned and consummatory responses

Abstract

Control of beak opening (gape) and peck location was examined in pigeons. Feeding pecks showed accurate guidance that positioned the seed between the beaks. At the moment of contact with the seed, gape was proportional to seed diameter, although pecks with gape less than seed diameter were more frequent following an increase in seed size during a meal. There were no substantial differences between pigeons trained to keypeck with autoshaping and those trained with operant conditioning procedures. With either procedure, water reinforcement produced keypecks with the beak closed; seed reinforcers of different sizes produced means for gape proportional to the seed diameters. Black or white circular stimuli of different sizes projected as conditioning signals had little influence upon gape, but a greater percentage of responses was directed to white stimuli. These results indicate that visual stimuli elicit and orient the peck, whereas the adjustment of gape also involves the somatosensory stimuli provided during previous experience with a particular reinforcer or food type. 223The beak of a bird is involved in a variety of behaviors, including eating and drinking, manipulation of nonfood objects (e.g., nest materials), care of the body surface (preening), and agonistic behavior. Considered as an effector organ, the avian beak has functions analogous to those of the hand. Indeed, during grasping the upper and lower beaks operate like the primate thumb and forefinger (Beecher, 1951). The complexity of such behaviors requires a system capable of precise motor organization. Moreover, as a component of both conditioned keypecks and consummatory responses, beak movements provide an important behavioral parameter for comparisons of conditioned and consummatory response forms. We have therefore begun to investigate the sensorimotor control of beak movements by examining the grasping behavior of the pigeon.Grasping is one of four components of the pigeon's feeding behavior sequence: pecking, grasping, mandibulation, and swallowing (Zeigler, 1976;Zweers, 1982b). High-speed cinematographic analyses indicate that grasping is integrated into the pecking response and may be divided into two distinct phases: beak opening and

Adjunctive behaviors are operants

“…Some of the variance in the time course of measured responding may be due to the stochastic engagement of these different forms of responding. These styles of responding depend in part on the nature of the reinforcer (Kohman, Leising, Shaffer, & Higa, 2006;LaMon & Zeigler, 1984). Because of this dependency, different reinforcers can be discounted at different rates (Smith & Renner, 1976;Staddon & Zhang, 1989), if the stylistic differences in the instrumental responses have different gradients.…”

Pigeons use distinct stop phases to control pecking

“…Closing the eyes just before the impact with a target probably protects them against possible back-scattering particles (Delius, 1985). The beak opening is proportional to the size of the seed at which the peck is aimed (Deich et al, 1985;LaMon and Zeigler, 1984). However, when pigeons peck at targets on a screen to obtain a water reward, the beak remains closed Zeigler, 1988, 1984).…”

Classical conditioning of jaw movements in the pigeon: Acquisition and response topography

“…Jaw movements during both eating and foodreinforced keypecking are episodic and vary in their peak gape amplitude with the size of the food pellet. Jaw movements during drinking and water-reinforced pecking are rhythmic, with small and relatively invariant peak gape amplitudes (LaMon & Zeigler, 1984, 1988.…”