Escape behavior as determined by schedules of shock and discrete CS presentations

Abstract

Rats received escape training, with shock-presentation schedules of 50% or 100% and discrete CS-presentation schedules of 0%, 50% or 100%, followed by extinction with the discrete CS alone. Acquisition performance was directly related to shock percentage (p < .001). No reliable effect of CS was found. Resistance to extinction was inversely related to shock percentage (p < .05) and, during early extinction, was directly related to CS percentage (p < .02 on extinction Trial Block I).In the instrumental shock-escape situation, fear, classically conditioned to the stimuli present at shock application, is presumed to be a partial determinant of escape performance. McAllister & McAllister (1962) have reported that better classical fear conditioning resulted from pairing shock with the combined stimuli of a discrete CS (light) and static visual and tactile cues of the conditioning box, than from pairing shock with static box cues alone. Thus, if McAllister and McAllister's findings were generalizable to shockescape behavior, one would predict that, all things constant, escape training with the combined stimuli of a discrete CS and static apparatus cues would be superior to training with static cues alone. The first purpose of this experiment was to investigate this hypothesis.The second purpose of this study was to investigate the effects of intermittent shock schedules on escape behavior, using a different intermittent schedule and more distributed acquisition and extinction sessions than were reported previously (e.g. Franchina, 1966). MethodThe apparatus was that described by Franchina (1966). A white start box was separated from a black safe box by a guillotine door and a hurdle. The start box floor could be electrified with 50-volts shock; the only resistance in the shock circuit was S. The safe box floor could be depressed.On top of the start and the safe boxes were compartments which served as lids and contained sources of illumination for the lower boxes. The source for intertrial illumination, 7 ft-c, was a 7-1/2-wattlampon the left wall of each lid, 16 in. above the floors of the lower boxes. The source for the discrete CS, an increase in start box illumination from 7 to 110 ft-c, was a 40-watt lamp on the right wall of the start box lid, 14 in. above the start box floor. The illumination was reflected from its source by an aluminum foil lining inside each lid. Frosted Plexiglas, 3/16 in. thick, diffused the illumination into the lower boxes.Psychon. Sci., 1966, Vol. :; (1) JOSEPH J. FRANCHINA SOUTHERN METHODIST UNIVERSITYSs were 84 naive, female, Holtzrtlan albino rats,100-110 days old at the start of the experiment. Ss were randomly and evenly distributed into a 3 by 2 design for escape training with shock presentation on 50% or 100% of the trials and discrete CS (light) presentation on 0%, 50% or 100% schedules. Static apparatus cues were constantly present in each CS (light) condition.Each S received 4 min. of exploration in each side of the apparatus followed, on the next day, by the start of escape tra...