When behavior suggests that the value of a reinforcer depends inversely on the value of the events that precede or follow it, the behavior has been described as a "contrast" effect. Three major forms of contrast have been studied: "incentive contrast," in which a downward (or upward) shift in the magnitude of reinforcement produces a relatively…

Mice from replicate lines, selectively bred based on high daily wheel-running rates, run more total revolutions and at higher average speeds than do mice from nonselected control lines. Based on this difference it was assumed that selected mice would find the opportunity to run in a wheel a more efficacious consequence. To assess this assumption…

One group of undergraduates responded under a fixed-ratio (FR) 25 schedule and a second group responded under a differential-reinforcement-of-low-rate (DRL) 5-s schedule (first history phase). Both groups of subjects were then exposed to a differential-reinforcement-of-other-behavior (DRO) 5-s schedule (second history phase), and finally to…

Exposure to an enriched environment (EE) has been shown to induce cortical plasticity. Considerable amount of research is focused on the effects of EE in the hippocampus; however, effects of EE on other brain regions and the mechanisms involved are not well known. To investigate this, we induced cortical plasticity by placing mice in an EE for one…

Research has suggested that rats increase their response rate for a low-valued reinforcer when a high-valued reinforcer will soon be available (i.e., positive induction) because the value of the low-valued substance has increased. The present study tested if such a procedure could be used to increase rats' responding for a non-reinforcing food.…

Using a context discrimination procedure and rats as the subjects, the formation of context-dependent aversions to novel and familiar fluids was investigated. Experiment 1 revealed that context dependency could be established to a novel fluid (saccharin) after three cycles of context discrimination training and that the acquired context dependency…

Three experiments examined the effects of physical context changes and multiple extinction contexts on the renewal of conditioned suppression in humans. A conditioned suppression task used an undesirable event as the unconditional stimulus (US). One conditional stimulus (CS+) predicted the occurrence of the US and another (CS-) predicted US…

Implicit measures such as the Implicit Association Test (OAT) have recently become popular as tools in research on evaluative conditioning. The reason is that these measures are thought to be impervious to changes in valence that are due to conscious propositional knowledge about the relation between the conditioned stimulus (CS) and the…

Fear conditioning is a popular model for investigating physiological and cellular mechanisms of memory formation. In this paradigm, a footshock is either systematically associated to a tone (paired conditioning) or is pseudorandomly distributed (unpaired conditioning). In the former procedure, the tone/shock association is acquired, whereas in the…

Much recent research on mechanisms of learning and memory focuses on the role of heterosynaptic neuromodulatory signaling. Such neuromodulation appears to stabilize Hebbian synaptic changes underlying associative learning, thereby extending memory. Previous comparisons of three related sea-hares (Mollusca, Opisthobranchia) uncovered interspecific…

In the present study, joint-control training was applied when teaching manded selection responses to children with autism. Four vocal children with autism participated in the first experiment, two males (ages seven and eight) and two females (ages seven and nine). The results showed that it was only after object-word naming was trained under joint…

Three-month-old infants learned to activate a crib mobile by means of operant footkicks. Retention of the conditioned response was assessed in the presence of the nonmoving mobile. Although forgetting is typically complete after an 8-day retention interval, infants who received a reactivation treatment, a brief exposure to the reinforcer 24 hours…

Presented is a series of studies in which the efficacy of applying operant conditioning methodologies to the problem of stuttering was examined. One requirement was that the designed therapeutic programs utilize only verbal contingent stimuli (reinforcers and punishers) in the traditional therapeutic setting (client and therapist seated together…

To obtain evidence linking long-term potentiation (LTP) and memory, we examined whether LTP induction modifies functional relationship among neurons in the rat hippocampus. In contrast to neurons in low-frequency stimulated or AP5-treated slices, LTP induction altered "functional connectivity," as defined by the degree of synchronous firing, among…

One conditioned taste aversion experiment with rats assessed the impact of extinguishing a target conditioned stimulus (CS), S, in compound with a second CS, A, upon conditioned responding elicited by CS S when presented alone at test. Following initial conditioning treatment with CSs A and S, the experiment manipulated number of extinction trials…