Suppression of corticosterone synthesis alters the behavior of hippocampally lesioned rats

The suppression of corticosterone synthesis with metyrapone (25 mg/kg) reduced the hyperactivity and altered the exploratory activity of hippocampally lesioned animals (HPC) in the open field to the level of cortical and sham controls (Experiment 1). In a second experiment, corticosterone (600 micrograms/kg) pretreatment 2 h, but not 1 h, before metyrapone partially restored the hyperactivity of HPC animals that had been decreased by the corticosteroid-suppressant drug. Alterations in exploratory behavior induced by metyrapone were also prevented by corticosterone pretreatment. The results suggest that the suppression of corticosterone in hippocampally lesioned animals produces a normalization of behavior that can be prevented by pretreatment with corticosterone.     

Correlates of adult and child perceptions of social competency

In this study, the relationship between two commonly used measures of social competency, peer ratings of perceived status and adult ratings of assertiveness, were examined. In Phase I, high and low sociometric status children were videotaped responding to a series of role-play scenes; performance on these scenes was then rated retrospectively by adults for overall assertiveness. In Phase II, a second group of children who were unfamiliar with the videotaped children observed the taped scenes and provided ratings of likability, intelligence, working together, and attractiveness. In general, results revealed that children and adults differed in their ratings of the videotaped children. Further, boys used different cues in their ratings than did girls. More specifically, the sociometric status of girls was related to perceived attractiveness, whereas the sociometric status of boys was more closely related to perceived intelligence. Such findings suggest that children and adults look for and use different cues in their judgments. Given these differences, it is concluded that child and adult ratings should not be used interchangeably in the assessment of, and evaluation of, social competency in children.Portions of this research were supported by a grant from the Virginia Department of Criminal Justice Services.     

Physical self-efficacy and actualization

In his theorizing about self-actualization, Maslow speculated that physical ability and physical self-confidence were two aspects of cooperative dominance which were associated positively with actualization. These aspects of dominance bear close resemblance to the Perceived Physical Ability (PPA) and the Physical Self-Presentation Confidence (PSPC) dimensions of the Physical Self-Efficacy (PSE) Inventory. Accordingly, the PPA and PSPC scores of undergraduate men and women were correlated with their scores on the Personal Orientation Inventory (POI), a popular measure of actualization, to test Maslow's hypotheses. The results showed that, contrary to Maslow's claims, PPA is not a positive correlate of self-actualization. However, strong support was found for Maslow's contention that high-PSPC individuals are more likely to be actualizing than low-PSPC people. Also, Maslow's hypothesis that actualizers are high in global sensation seeking (SS) was tested. The data indicated that only male actualizers were high in various aspects of SS, but female actualizers were not. Multiple regression analyses revealed further that both SS and PSPC are primary contributors to POI for men, but only PSPC contributes significantly to POI for women. Discussion focused on the reasons why research findings showing that increases in physical fitness lead to increases in self-esteem cannot be used to support the view that physical fitness and actualization are linked positively.     

The effects of display and report order asymmetries on lateralized word recognition

Word recognition typically is better or faster in the right visual field than in the left visual field, an effect that often interacts with the handedness of subjects or the phonetic characteristics of the language employed. While these findings suggest a hemispheric locus, it is possible that the field difference is confounded with display or report order asymmetries. Here two experiments manipulate word orientation (horizontal vs. vertical), letter symmetry, and report order variables, and they demonstrate a generalized right field superiority that fails to interact with other factors. Since the superiority appears even when all apparent artifactual asymmetries are eliminated, the findings support a hemispheric interpretation.     

Evidence for scanning with unilateral visual presentation of letters

When letters and words are presented tachistoscopically, material from the right visual field (RVF) can be reported more accurately than that from the left visual field (LVF). The RVF superiority may reflect either left hemispheric dominance for language or directional scanning. Previous studies have deliberately focused on the cerebral asymmetry factor while "controlling" scanning and, thus, have cast some doubt on the potency of the scanning factor. Two experiments were conducted to show that scanning can induce a RVF superiority comparable to that often associated with cerebral asymmetry. The first experiment required bilingual subjects to report six English or six Hebrew letters, shown briefly in either the LVF or RVF, with order of report controlled. A RVF superiority found with English characters was matched by an equal but opposite LVF effect with Hebrew. In a second experiment, five English characters were shown briefly in either the LVF or RVF, and subjects had to identify a single character indicated by a post exposural cue. Using a spatial cue to by pass scanning, there were no field differences; with an ordinal position cue--a procedure thought to force scanning--there was a strong RVF superiority. The results show clearly that scanning can induce visual field differences.     

A secondary-task analysis of a word familiarity effect

In three experiments we examined aspects of the word inferiority effect and word frequency disadvantage for letter detection. In Experiment 1 we tested a prediction derived from a hypothesis based solely on attentional factors. Adult subjects performed one of two secondary detection tasks while reading for comprehension. The inferiority effects were obtained only when the secondary task was letter detection, not when nonletter targets were used in the secondary task. This finding is inconsistent with the attentional hypothesis, but is consistent with the unitization hypothesis of Healy and Drewnowski (1983). In Experiments 2 and 3 we found that manipulation of the need to read for comprehension had little influence on the letter-detection inferiority effects, but a strong influence on the effects involving the detection of nonletter targets. These results are discussed in terms of their implications concerning processing system flexibility.     

Distributed memory and the representation of general and specific information

We describe a distributed model of information processing and memory and apply it to the representation of general and specific information. The model consists of a large number of simple processing elements which send excitatory and inhibitory signals to each other via modifiable connections. Information processing is thought of as the process whereby patterns of activation are formed over the units in the model through their excitatory and inhibitory interactions. The memory trace of a processing event is the change or increment to the strengths of the interconnections that results from the processing event. The traces of separate events are superimposed on each other in the values of the connection strengths that result from the entire set of traces stored in the memory. The model is applied to a number of findings related to the question of whether we store abstract representations or an enumeration of specific experiences in memory. The model simulates the results of a number of important experiments which have been taken as evidence for the enumeration of specific experiences. At the same time, it shows how the functional equivalent of abstract representations--prototypes, logogens, and even rules--can emerge from the superposition of traces of specific experiences, when the conditions are right for this to happen. In essence, the model captures the structure present in a set of input patterns; thus, it behaves as though it had learned prototypes or rules, to the extent that the structure of the environment it has learned about can be captured by describing it in terms of these abstractions.     

A computational analysis of mental image generation: evidence from functional dissociations in split-brain patients

Recent efforts to build computer simulation models of mental imagery have suggested that imagery is not a unitary phenomenon. Rather, such efforts have led to a modular analysis of the image-generation process, with separate modules that can activate visual memories, inspect parts of imaged patterns, and arrange separate parts into a composite image. This idea was supported by the finding of functional dissociations between the kinds of imagery tasks that could be performed in the left and right cerebral hemispheres of two patients who had previously undergone surgical transection of their corpus callosa. The left hemisphere in both subjects could inspect imaged patterns and could generate single and multipart images. In contrast, although the right hemisphere could inspect imaged patterns and could generate images of overall shape, it had difficulty in generating multipart images. The results suggest a deficit in the module that arranges parts into a composite. The observed pattern of deficits and abilities implied that this module is not used in language, visual perception, or drawing. Furthermore, the results suggest that the basis for this deficit is not a difficulty in simply remembering visual details or engaging in sequential processing.     

Potentiation and overshadowing in preweanling and adult rats

Four experiments compared the aversion acquired by 18-day-old and 60-day-old rats to a flavor that was either tasted alone or in combination, simultaneously or successively, with another flavor when paired with illness. The purpose was to study temporal variables and theoretical issues pertinent to potentiation and overshadowing while investigating ontogenetic differences in these phenomena. When either the preweanlings or the adults were presented a simultaneous compound flavor (sucrose/coffee) followed by lithium chloride-induced illness, greater sucrose aversions were found than for animals conditioned on sucrose alone--that is, potentiation. Preweanlings demonstrated greater potentiation than did adults, whether the conditioned stimulus-unconditioned stimulus (CS-US) delay was 0 or 1 hr. This potentiation was eliminated by nonreinforced presentations of the alternative CS element. Potentiation was not seen when the two flavors were presented successively as the CS; instead, overshadowing occurred. Tests of configuring by extinction procedures indicated a tendency for these animals to form a configured representation of the simultaneous compound solution. This disposition for configuring tended to be more pronounced for preweanlings than for adults. Ontogenetic differences in response to configuration, CS saliency, and generalization decrement seem consistent with at least one model of potentiation and the ontogenetic differences in potentiation seen in the present experiments.     

Discrimination of letters and random dot patterns by pigeons and humans

In a three-choice discrimination task, pigeons learned to distinguish each letter of the alphabet from all the other letters and each of 16 random dot patterns from all the others. Discrimination errors were used to generate a matrix of interletter and interpattern similarities. Human estimates of letter similarity were obtained from the literature, and human subjects rated the similarity of the dot patterns. Pigeon and human performances were described and compared through correlation, multidimensional scaling, and cluster analysis. Fits of the data by simple-feature and template models were computed and compared. The correlation between pigeon and human similarity matrices was .68 for letters and .72 for dot patterns. The other analyses revealed broadly similar patterns of results from the two species but suggested also that, relative to human data, the best fits to the pigeon data required fewer dimensions, fewer features, and fuzzier templates. There was some indication that pigeon discriminations depended on relatively simple features, and several of these were tentatively identified. The different methods employed might have influenced these apparent differences between pigeons and humans, but, overall, the results suggest considerable cross-task and cross species generality in the processing of these simple forms.