Secondary reinforcement and rate of primary reinforcement

Four pigeons were trained to peck at either of two response-keys. Pecking at either key occasionally produced a secondary reinforcer. Then, in the presence of the secondary reinforcer, further pecking occasionally produced the primary reinforcer, food. The relative rate at which each pigeon pecked to obtain a secondary reinforcer equalled the relative rate of primary reinforcement in its presence.     

Conditioned reinforcement and discrimination performance

Pigeons were trained in a three-key chamber to peck one side key in the presence of a vertical line on the center key and to peck the other side key in the presence of a horizontal line. Correct choice responses were reinforced with food according to fixed- and variable-ratio, fixed-interval, and differential-reinforcement-of-long-latency schedules of reinforcement. For each schedule, the birds performed under each of two conditions: (1) each correct choice response produced a brief presentation of stimuli intermittently paired with food, then the next trial; (2) each correct choice response produced an intertrial interval only. For all schedules except one long latency schedule, response rates were higher under the condition of brief stimulus presentation than under the comparable control condition. Presentation of brief magazine stimuli increased choice accuracy. The amount of change in accuracy was correlated with the rate of food presentation. Performance under the schedules with highest food reinforcement rates showed no enhancement; performance under the schedules with the lowest reinforcement rates showed the greatest enhancement.     

Adventitious reinforcement in free-operant discrimination

The discriminative performance of rats trained under conditions in which their responses to S? postponed the appearance of S+, both for themselves and for yoked-control animals, was found to be superior to the performance of the controls in two rather different experiments. The results demonstrate the pervasiveness of adventitious reinforcement in free-operant discrimination.     

Extinction learning, reconsolidation and the internal reinforcement hypothesis

Retrieving a consolidated memory--by exposing an animal to the learned stimulus but not to the associated reinforcement--leads to two opposing processes: one that weakens the old memory as a result of extinction learning, and another that strengthens the old, already-consolidated memory as a result of some less well-understood form of learning. This latter process of memory strengthening is often referred to as "reconsolidation", since protein synthesis can inhibit this form of memory formation. Although the behavioral phenomena of the two antagonizing forms of learning are well documented, the mechanisms behind the corresponding processes of memory formation are still quite controversial. Referring to results of extinction/reconsolidation experiments in honeybees, we argue that two opposing learning processes--with their respective consolidation phases and memories--are initiated by retrieval trials: extinction learning and reminder learning, the latter leading to the phenomenon of spontaneous recovery from extinction, a process that can be blocked with protein synthesis inhibition.     

Secondary reinforcement and number of primary reinforcements

Pigeons' pecks on either of two concurrently available response keys produced secondary reinforcers according to independent one-minute variable-interval schedules. Different secondary reinforcers, in the presence of which the rates of primary reinforcement were equal, were associated with each key. The rate of pecking maintained by each secondary reinforcer varied directly, but nonproportionally, with the number of primary reinforcements given in the presence of the secondary reinforcer.     

Fixed-ratio discrimination: effects of intermittent reinforcement

Four pigeons had discrimination training that required the choice of a left side-key after completing a fixed-ratio 10 on the center key, and a right side-key choice after fixed-ratio 20. Correct choices were reinforced on various fixed-interval, fixed-ratio, random-interval, and random-ratio schedules. When performance was examined across successive 15-second intervals (fixed-interval and fixed-ratio schedules) accuracy was high in the first 15-second interval, decreased in one or several of the next 15-second intervals, and then increased again as reinforcement was approached. When performance was examined across correct trials on fixed-interval and fixed-ratio schedules, accuracy was lowest immediately after reinforcement, followed by a systematic increase in accuracy as the number of correct choices increased. These patterns were due primarily to errors on fixed-ratio 20 trials. Systematic accuracy patterns did not occur on random-interval or random-ratio schedules. The results indicate that when choice patterns differed on fixed-interval and fixed-ratio schedules, the differences were due to the method of data analysis.