Associations in human instrumental conditioning

Four experiments were conducted to study the contents of human instrumental conditioning. Experiment 1 found positive transfer between a discriminative stimulus (S^D) and an instrumental response (R) that shared the outcome (O) with the response that was originally trained with the S^D, showing the formation of an S^D → O association. Experiment 2 found that post-acquisition devaluation of an outcome selectively reduced the response trained with that outcome, showing the formation of a R → O association. In Experiment 3, changing the outcome did not prevent participants from giving the response learned with each S^D, even though none of the responses was appropriate for the new outcome, showing evidence of the formation of S^D → R associations in instrumental learning. The three binary associations were shown within the same basic experimental situation. Finally, Experiment 4 found evidence of the formation of the higher order association S^D(R → O) in human instrumental conditioning.     

Contiguity and contingency in instrumental conditioning

There have been several attempts to construct molar theories of conditioning on the empirical basis that response-reinforcement contingency is important in determining conditioning. Such theories claim to explain behavior in terms of molar level processes which transcend the molecular level and, therefore, are not reducible to molecular processes or their interaction. These molar theories are critically examined and found to be seriously flawed because they fail to account for the effects of delaying reinforcement (degree of contiguity). Observed molar level relations, such as the matching law, do not require a molar theory, but may be more usefully considered as a product of molecular processes.     

Partial reinforcement effects in instrumental escape conditioning

In Experiment I acquisition and extinction of instrumental escape conditioning with rats (N = 64) were studied as a function of reinforcement magnitude under conditions of partial and continuous reinforcement. In Experiment II the effects of partial and continuous reinforcement were studied in rats (N = 96) during acquisition followed by small, medium, and large reductions in reinforcement magnitude. A water-tank escape apparatus was used with temperature as the relevant variable. It was found that (1) with large reinforcement magnitude a continuously reinforced group was superior in acquisition to one that was partially reinforced; there were no differences with small reinforcement; (2) disruptive effects of a nonreinforced trial (a) appear early in learning, (b) are quite strong after each nonreinforced trial, and (c) persist through several succeeding reinforced trials; (3) major competing behaviors persist throughout acquisition for small reinforcement magnitude regardless of schedule, decline with large reinforcement (more so with continuous than with partial), and return to a high level in extinction for all conditions; (4) the partial reinforcement extinction effect occurs after large reinforcement but not after small, and it appears only with large reductions in reinforcement magnitude which approach extinction conditions. Only the first part of the last finding appears to be consistent with the appetitive conditioning literature.     

The pavlovian analysis of instrumental conditioning

An account was given of the development within the Russian literature of a uniprocess formulation of classical and instrumental conditioning, known as the bidirectional conditioning hypothesis. The hypothesis purports to offer a single set of Pavlovian principles to account for both paradigms, based upon a neural model which assumes that bidirectional (forward and backward) connections are formed in both classical and instrumental conditioning situations. In instrumental conditioning, the bidirectional connections are hypothesized to be simply more complex than those in classical conditioning, and any differences in empirical functions are presumed to lie not in difference in mechanism, but in the strength of the forward and backward connections. Although bidirectional connections are assumed to develop in instrumental conditioning, the experimental investigation of the bidirectional conditioning hypothesis has been essentially restricted to the classical conditioning operations of pairing two CSs (sensory preconditioning training), a US followed by a CS (backward conditioning training) and two USs. However, the paradigm involving the pairing of two USs, because of theoretical and analytical considerations, is the one most commonly employed by Russian investigators. The results of an initial experiment involving the pairing of two USs, and reference to the results of a more extensive investigation, leads us to tentatively question the validity of the bidirectional conditioning account of instrumental conditioning.     

Contextual conditioning and reinstatement of extinguished instrumental responding

In three experiments we studied the relationship between contextual conditioning and the reinstatement of extinguished lever pressing that occurs when noncontingent food is introduced following extinction. In all three experiments the non-contingent food was presented off-baseline (with the response levers not present). On subsequent tests, with the response levers present, animals that had been exposed to food showed more reinstatement of lever pressing than control animals. This finding rules out alternative mechanisms for the reinstated responding that rely on the interaction of non-contingent food and responding, such as superstitious reinforcement or the discriminative after-effects of food. In addition, in each experiment we demonstrated that manipulations known to affect contextual conditioning (signalling the food in Experiment 1, context extinction in Experiment 2, and switching contexts in Experiment 3) reduced the reinstatement. These results are consistent with the claim that contextual conditioning is important in controlling instrumental conditioning and closely parallel findings concerning the reinstatement of Pavlovian responsing following extinction.     

The inhibitory effect of pretrial reinforcement on instrumental conditioning

It has been shown previously that pretrial feeding retards acquisition of an instrumental response. The present experiment tested three hypotheses for this effect: priming, overshadowing and conditioned inhibition. Rats were trained in a runway task with a partial schedule of food reinforcement. Rats that were prefed immediately prior to rewarded trials showed a decrement in acquisition when compared with subjects prefed 180 seconds pretrial. Other subjects prefed immediately prior to nonrewarded trials showed a similar decrement in acquisition, even though the pretrial and goal reinforcers occurred on separate trials. Thus, the adverse effects of prefeeding occurred in the absence of conditions necessary for priming or overshadowing to occur. The results suggest there may be an inhibitory aftereffect of food rewards which can become conditioned to subsequent stimuli.     

Disinhibition in pitch memory

Recognition of the pitch of a tone is disrupted by the interpolation of other tones during the retention interval. The disruptive effect of an interpolated tone varies systematically as a function of its pitch relationship to the tone to be remembered, and is maximal at a 2/3-tone separation. When such a tone is interpolated, the interpolation in addition of a further tone that is 2/3 tone removed from this disruptive tone (and 4/3 tone removed from the tone to be remembered) causes recognition of the first tone substantially to return. When recognition performance is plotted as a function of the pitch relationship between these two interpolated tones, the results accord well with a model assuming mutual inhibitory interactions between pitch memory elements.