Contextual control over conditioned responding in a latent inhibition paradigm.

We used 1-, 2-, and 3-context designs to study the control exerted by contexts over freezing in rats exposed to a conditioned stimulus (CS) in advance of its pairing with a shock unconditioned stimulus. The latent inhibition observed when preexposure, conditioning, and testing occurred in the same context was attenuated if preexposure occurred in a different context to conditioning and testing. Latent inhibition (i.e., attenuated performance) was restored in a CS-specific manner if preexposure and testing occurred in the same context and conditioning in a different one. Latent inhibition was also reduced by a long retention interval but remained specific for a particular context-CS relation. Finally, CS preexposure resulted in contextual control over the expression of excitatory conditioned performance. The results are discussed in terms of memory, associative, and associative-performance models of CS-preexposure effects.

Contextual control over conditioned responding in an extinction paradigm.

Four experiments studied contextual control over rats' freezing to conditioned stimuli (CSs) that had been paired with shock and were then extinguished. In Experiment 1, rats were exposed to a CS A-shock and a CS B-shock pairing in Context C. CS A was then extinguished in Context A, and CS B in Context B. Freezing was renewed when each CS was presented in the context where the other CS had been extinguished. In Experiments 2-4, rats were exposed to a CS A-shock pairing in A and a CS B-shock pairing in B. They were then exposed to Context C where one, both, or neither of the CSs were extinguished, or where both CSs continued to be reinforced. On test, the rats froze more to CS A than to CS B in Context A, and more to CS B than to CS A in Context B, but only if the CSs had been extinguished. Thus, after extinction, rats use contexts to regulate retrieval not only of their memory for extinction, but also of their memory for the original conditioning episode.

Motivational state regulates the content of learned flavor preferences.

Rats acquired a preference for an aqueous odor (almond) presented in simultaneous compound with sucrose. Separate presentations of saccharin reduced this preference in rats with ad-lib access to food during training or at test, but not in rats that were hungry during both training and test. In contrast, separate presentations of sucrose reduced the preference for the almond irrespective of deprivation state during training and test. We interpret the results to mean that a hungry rat forms odor-taste and odor-calorie associations, and its motivational state on test determines which of these associations controls the preference. In contrast, a rat that is not hungry during training only forms an odor-taste association, and its performance on test is independent of its level of hunger.

Classroom environment and locus of control in identifying high and low self-concept in fourth- and fifth-graders.

This study examined classroom environment and locus of control in identifying successfully children showing high and low self-concepts. In their respective intact classrooms, 107 fourth- and fifth-graders were administered the Piers-Harris Children's Self-concept Scale, the Classroom Environment Scale, and the Nowicki-Strickland Children's Locus of Control Scale. A stepwise discriminant analysis indicated that four variables in combination successfully classified 76% all cases, suggesting the importance of environmental factors associated with classrooms and locus of control in identifying self-concepts of children of elementary-school age.

Enteritis due to Salmonella panama from infected ham.

After the appearance of sporadic cases of enteritis due to Salmonella panama, baked ham from one supplier was implicated as the source of infection. No pathogenic organisms were isolated from the working surfaces of the factory involved or from samples of a day's bacon output, but S. panama was isolated from the factory sewers. Stool examinations of the 500 employees showed one man in the baked ham section to be excreting S. panama. He was removed from work and no further infections were reported from the district. The organism could no longer be found in the sewers.Some weeks later, further infections were reported in the London and Southend areas, which could be traced to ham from the original source. Sewer swabs at the factory were again positive. A further examination of all the employees revealed three cases and 82 symptomless excretors. Eight of 192 family contacts were also found to be excretors. Trimethoprim-sulphamethoxazole appeared to have no effect on the carrier state.Examination of the hams in cold store showed some to be infected with S. panama, and a number of these had been consumed in the canteen.Subsequent examination of pigs at slaughter and pig food prepared locally failed to isolate S. panama. The source of infection at the factory is unknown.