A note on the interpretation of the factor pattern of the California Psychological Inventory

The intercorrelation matrix between the scales of the California Psychological Inventory, given in the manual, was factor analyzed. Three factors were extracted and rotated by varimax. The matrix was rescaled, first normalizing the rows, then standardizing the columns to a mean sum of squares of one. Unity was used as a cut-off point for determination of salient loadings. The first two factors were similar to the results reported in a previous Study by Nichols and Schnell. The third factor was interpreted as an independence-dependence dimension.     

Developmental differences in subjects' associative-learning strategies and performance: Assessing a hypothesis

Fifth-, seventh-, and ninth-grade (11-, 13-, and 15-year-old) subjects were presented with a list of paired associates to learn and were interviewed about the strategies used to learn them. Although a majority of fifth graders reported simply rehearsing the pairs in order to remember them, very few ninth graders relied exclusively on rehearsal. Consistent with a hypothesis advanced by Rohwer (1973), the number of subjects who elaborated some or all of the pairs increased with age. Paired-associate performance increased with age, but the level of paired-associate learning was much more related to the type of strategy reported by the subject than to the age of the subject per se.     

Additional evidence from a paradigm for inferring discriminative processes in children and adults

A previously developed paradigm which incorporates a correlational methodology into an experimental context was used in the present study to specify more definitely the attribute(s) underlying verbal discrimination learning under normal conditions. In the case of fifth- and sixth-grade children, it was found that frequency theory is sufficient to account for performance on the task. However, older subjects were less homogeneously reliant on the frequency attribute. While many older subjects appeared to utilize frequency cues, others adopted strategies that resulted in the utilization of attributes other than frequency.     

MMPI differences among mild and severe insomniacs and good sleepers

Past research has attempted to delineate personality differences between insomniacs and good sleepers but has failed to control for type of insomnia or severity of the disorder. The purpose of this study was to compare MMPI scores of mild and severe sleep onset insomniacs with a control group of noninsomniacs . Results demonstrated that sleep onset insomniacs, regardless of degree of severity, differed significantly from noninsomniacs ; and that mild and severe insomniacs differed from each other on only one MMPI scale.     

Characterization of the cognitive effects of combined muscarinic and nicotinic blockade

Choice accuracy performance in the radial-arm maze is dependent upon the integrity of both the nicotinic and muscarinic cholinergic receptors. Pharmacological blockade of either of these subtypes of cholinergic receptors with mecamylamine or scopolamine impairs choice accuracy in the radial-arm maze. We have previously demonstrated that the performance deficit caused by muscarinic blockade is exacerbated in at least an additive fashion by coadministration of the nicotinic antagonist, mecamylamine. In the present study, it was found that mecamylamine and scopolamine act together in a greater than additive fashion in disrupting radial-arm maze choice accuracy. When doses of these drugs which do not by themselves cause significant impairments in choice accuracy are given together, they induce a pronounced impairment. Previous results have shown that the adverse effects of nicotinic blockade could be reversed by the dopaminergic D2 agonist LY 171555. In this study, this drug was found to attenuate the cognitive impairment caused by combined nicotinic and muscarinic blockade. On the other hand, the dopaminergic D1 antagonist SCH 23390 which has previously been shown to reverse the adverse effects of muscarinic blockade was not found in this study to attenuate the impairment of combined nicotinic and muscarinic blockade. Since combined nicotinic and muscarinic blockade approximates generalized cholinergic underactivation, treatments like LY 171555, which attenuate the adverse effects of this combined blockade, may be useful in treating syndromes like Alzheimer's disease, which are characterized by generalized cholinergic loss.     

Focal lung pathology detection in radiology: Is there an effect of experience on visual search behavior?

In radiology, 60% to 80% of diagnostic errors are perceptual. The use of more efficient visual search behaviors is expected to reduce these errors. We collected eye-tracking data from participants with different levels of experience when interpreting chest X-rays during the completion of a pathology-detection task. Eye-tracking measures were assessed in the context of three existing visual search theories from the literature to understand the association between visual search behavior and underlying processes: the long-term working memory theory, the information-reduction hypothesis, and the holistic model of image perception. The most experienced participants (radiology residents) showed the highest level of performance, albeit their visual search behaviors did not differ from the intermediate group. This suggests that radiology residents better processed the represented information on the X-ray, using a visual search strategy similar to the intermediate group. Since similar visual search resulted in more information extraction in the radiology residents compared with the intermediates, we suggest that this result might support the long-term working memory theory. Furthermore, compared with novices, intermediates and radiology residents fixated longer on areas that were more important to avoid missing any pathology, which possibly confirms the information-reduction hypothesis. Finally, the larger distances between fixations observed in more experienced participants could support the holistic model of image perception. In addition, measures of generic skills were related to a lower time cost for switching between global and local information processing. Our findings suggest that the three theories may be complementary in chest X-ray interpretation. Therefore, a unified theory explaining perceptual-cognitive superiority in radiology is considered.

     

Impaired discourse gist and working memory in children after brain injury

Emerging evidence suggests that a traumatic brain injury (TBI) in childhood may disrupt the ability to abstract the central meaning or gist-based memory from connected language (discourse). The current study adopts a novel approach to elucidate the role of immediate and working memory processes in producing a cohesive and coherent gist-based text in the form of a summary in children with mild and severe TBI as compared to typically developing children, ages 8-14 years at test. Both TBI groups showed decreased performance on a summary production task as well as retrieval of specific content from a long narrative. Working memory on n-back tasks was also impaired in children with severe TBI, whereas immediate memory performance for recall of a simple word list in both TBI groups was comparable to controls. Interestingly, working memory, but not simple immediate memory for a word list, was significantly correlated with summarization ability and ability to recall discourse content.     

Spatial and non-spatial visual discrimination learning in zebrafish (Danio rerio)

Zebrafish (Danio rerio) provide an excellent model for assessment of molecular processes of neurodevelopment. To determine the functional importance of molecular events during neurodevelopment, we have developed methods for assessing learning in zebrafish in a three-chambered fish tank. In the first study, simple escape response was assessed. Zebrafish tested with a moving net learned to escape to another chamber more rapidly over the six sessions of training than the fish with the still net which did not learn. Upon reversal of the contingencies, the fish switched to the inactive net rapidly learned to suppress the escape response and fish formerly in the inactive net condition learned to avoid the moving net. In the second study, spatial discrimination learning was assessed. Zebrafish were trained on a right-left position discrimination to avoid the active net. Zebrafish showed significant improvement in escape responses over six sessions of training with three trials per session. In the third study, red-blue non-spatial discrimination learning was assessed. There was a significant improvement over the first six training sessions. With the reversal of contingencies, there was a significant decline of performance. With continued training, the fish again significantly improved avoidance. These studies found an effective motivational stimulus and procedure for studying escape behavior in zebrafish; a procedure whereby zebrafish would learn both spatial and non-spatial discrimination. These methods are being developed to help determine the functional importance of molecular events during zebrafish neurodevelopment. Accepted after revision: 20 August 2001 Electronic Publication