Discontinuing positive reinforcement has been shown to elicit fighting in hooded rats, and to be associated with a transitory increase in the vigor and rate of the previously reinforced operant. The present study shows that the tendency for response frequency to increase and the tendency to attack covary following extinction-onset. It is also shown that, as the augmented response rate decreases, the tendency to attack diminishes and that the former change precedes the latter change.Withholding positive reinforcement after a history of reinforcement contingent on emission of an operant is associated with a transitory increase in response rate, force and duration (Notterman, 1959; Margulies, 1960), Azrin, Hutchinson, & Hake (1965) found that pigeons subjected to brief extinction periods would attack a stuffed dummy of a pigeon mounted on a switch in the test chamber. The specific relation between such extinction-induced attack and increased response rate and duration is, however, not clear.Previous studies by Thompson (1961Thompson ( , 1962 and Thompson, Heistad, & Palermo (1963) have dealt with changes in response rate and duration of operants during extinction. The purpose of the present research was to examine the covariation between the duration of fighting and the tendency for response rate to increase following extinction onset. In addition, the changes in both variables as a consequence of repeated exposure to nonreinforcement were explored. In this method, fooddeprived rats were conditioned on a regular foodreinforcement SChedule. A satiated animal was subsequently introduced into the test chamber along with the food-deprived animal, and training sessions were continued until the presence of the satiated animal had no discernible effect on the stability of lev~r-pressing performance. Then a series of extinction and reconditioning sessions were run, and response-frequency changes and the duration of fighting were recorded. Progressive changes in fighting and extinction-induced rate increase were examined over a series of successive extinctions and reconditioning sessions.Subjects. Two male hooded rats, weighing 380 and 360 gm respectively, served as experimental Ss, and two additional male hooded rats, weighing 355 and 345 gm respectively, served as objects of attack during extinction periods.Apparatus. A Foringer rat test chamber, equipped with a microswitch lever, a feeder, house lights, and an exhaust fan, served as the experimental apparatus. The test chamber was connected with relay-timer switching apparatus which arranged reinforcement and extinction contingencies. and recorded responses. The animals were fed Purina Fox Chow in their home cages and received 45-mg Noyes rat pellets in the experimental situation. The test chambers were Psychon. Sci.. 1966, Vol. 5 (9)
TRAVIS THOMPSON AND WILLIAM BLOOMUNIVERSITY OF MINNESOTA situated in a room adjacent to the programming and recording equipment, providing some sound attenuation.Procedure. The rats were systematically deprived of food until their weights d...