Charles N. Uhl

Eliminating behavior with omission and extinction after varying amounts of training

After rats were trained to leverpress for 1, 3, 9, or 27 days on a variable interval reinforcement schedule, omission training was compared with extinction in effectiveness of response elimination. Extinction produced faster response elimination than omission, although both procedures eventually led to equal response elimination. Resistance to response elimination increased with length of baseline training, although this effect did not interact with omission vs extinction. A test of the durability of elimination effects followed, using a response-independent variable time reinforcement schedule. After extinction, resumption of responding in the durability test increased with length of baseline training, but there was little response resumption following omission regardless of the length of the baseline training. These results amplify and extend previous findings which show omission to be an effective and durable response elimination method.

Response elimination in rats with schedules of omission training, including yoked and response-independent reinforcement comparisons

Abstract After rats were trained to lever press, response elimination began with factorial combinations of fixed vs variable and adjusting vs constant omission training schedules. A time interval scheduling reinforcement remained the same in a constant schedule, and its length was increased as response rate declined in the adjusting schedule. A variable time (VT) response-independent reinforcement schedule followed response elimination to test the durability of response cessation. Experiment I included groups whose reinforcement was yoked to that received by the omission schedule groups. Rate of response elimination was faster with an adjusting than a constant schedule, and slightly faster with a variable than a fixed schedule. There were no significant differences in rate of response elimination between omission schedule and yoked groups. Shorter delay of reinforcement tended to increase rate of response elimination. In the subsequent VT durability test all groups displayed near-zero response rates. In Experiment II adjusting fixed and variable omission schedules, including yoked groups, were compared with fixed time (FT) and VT reinforcement schedules. Response elimination was slower in the FT and VT groups, and they responded more in a subsequent VT durability test. It was concluded that differential reinforcement of other behavior fails to account for these omission training effects, and suggestions were made for an analysis based on the correlation between response and reinforcement rate.

Omission training compared with yoked controls and extinction in multiple-schedule discrimination learning*

After rats were trained on a multiple schedule with variable interval 30-sec reinforcement in both stimulus components, omission, yoked, and extinction procedures were applied in S− while the variable interval continued in S+. In S−, omission training reduced response rate faster and to a lower terminal level than either response-independent yoked reinforcement or extinction, which were approximately equivalent. In S+, the extinction group exhibited elevated response rates representing behavioral contrast, while the omission and yoked groups showed reduced response rates. These results attest to the effectiveness of omission training as a response elimination method. They also contradict theories which posit reduction of response rate in S− to be necessary and sufficient for behavioral contrast.

Relative persistence of avoidance and positively reinforced behavior

Abstract In one experiment with rats, and a second with pigeons, subjects were trained on a schedule in which identical response dependencies applied to intermittent receipt of positive reinforcement (PR) for one group and avoidance (AV) of shock for a second group. After obtaining comparable stable training performance for groups PR and AV, persistence tests were conducted with a traditional extinction (EXT) procedure vs. response-independent (FREE) delivery of positive reinforcers or shocks. In both experiments, response elimination was rapid in EXT for groups PR and AV, and responding tended to be maintained in groups PR and AV in the FREE persistence test. These results contradict the widely held assumption that avoidance behavior is unusually resistant to extinction, and they call for a re-examination of elimination of avoidance responding.

Effects of Overtraining on Reversal and Nonreversal Discrimination Shifts in a Free Operant Situation

Rats were trained on a single-stimulus, successive discrimination in a free operant situation. An irrelevant stimulus dimension was present at ail times. Following attainment of the acquisition criterion, Ss were shifted immediately or given 4 or 8 days of overtraining before being shifted. Half of Ss were given a reversal shift and half a nonreversal shift. Overtraining did not affect reversal or nonreversal learning. These results were contrasted with those of Mackintosh (1962). Various theoretical issues were discussed in light of the present findings. It was tentatively concluded that the overtraining effect depends upon the role of observing behavior in the formation and overtraining of a discrimination.

Persistence in punishment and extinction testing as a function of percentages of punishment and reward in training

Rat Ss were trained in a Skinner-box fixed ratio analogue of the straight runway. A 3 by 2 by 2 factorial design incorporated 0%, 50%, and 100% punished trials, 50% and 100% reinforcement with sucrose solution, and punishment vs. no punishment in extinction testing. Amount of responding in extinction testing increased with percentage of punishment and decreased with percentage of reinforcement.

Effects of time out and S+ postponement training procedures on free operant discrimination acquisition

Rat Ss received free operant discrimination training in which: (1) imposing a time out before each S+ period and (2) an S+ postponement contingency for responding late in S-periods were used to ascertain effects of adventitious reinforcement of S- responding by the appearance of S+ (a conditioned reinforcer). Postponement training was more effective than time-out training. The effectiveness of S+ postponement training appeared to be due to a massing of extinction resulting from prolonged S- periods early in training. There was no evidence that S+ conditioned reinforcement interfered with discrimination acquisition.

Single-alternation patterning in a conditioned suppression procedure with and without trace stimulus support

Rats in a conditioned suppression situation received an electric grid shock unconditioned stimulus (US) after every other conditioned stimulus (CS) for a total of 300 trials. These rats failed to show any evidence of single-alternation patterning. Thus, they did not suppress more to CSs paired with shock (R trials) than to CSs that were unpaired (N trials). Even when only R trials or only N trials were preceded by a salient predictive cue, only half the rats tested suppressed more on R trials than on N trials. These differences in responding were not large and developed late in training. It appears, therefore, that the stimulus traces of R and N trials do not exert much control in a “typical” conditioned suppression situation.

Overtraining Effects on Reversal and Nonreversal Discrimination Shifts with a Continuously Reinforced Free Operant

Rats were trained on a single-stimulus, successive discrimination in a free operant situation with continuous reinforcement of responding to S+. Ss were given 0, 4, or 8 days of overtraining (OT) after reaching the discrimination criterion. Half of the Ss were given a reversal shift (RS) and half a nonreversal shift (NRS). An irrelevant stimulus dimension was present at all times in Exp. 1, and it was absent in Exp. 2. OT did not affect RS or NRS learning in either experiment. NRS learning was faster than RS learning. These results were contrasted with other studies which have reported that OT facilitated RS learning and impeded NRS learning. Certain theoretical interpretations of discrimination learning, particularly Sutherlands treatment of centrally mediated attentional mechanisms, were critically discussed in light of the present findings.