Regression analyses of verbal learning on adult age at two anticiptation intervals.
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Normal, autistic and deaf children were tested for their immediate memory of visually presented digits. The digits were exposed either with or without a left to right spatial display arrangement, and had to be recalled forewards as well as backwards. Normal and deaf children tended to be sensitive to both display conditions and recall requirements whereas autistic children were mainly affected by direction of recall. Serial position effects in the normal and deaf groups were more dependent on order of retrieval than on input order.
Three experiments examined the effects of stimulus novelty and significance on the skin conductance component of the orienting response. The test stimuli used in the different experiments involved either a neutral change in stimulation (i.e., adding or deleting components to the standard stimuli), or an introduction of a significant element to the standard stimulus. The serial position of the test stimulus was manipulated in all three experiments. In Experiment 1, nonsignificant test stimuli were introduced at the second, fourth, sixth, or eighth trial of the complex sequence of eight stimuli (i.e., a sequence comprised of varying standard stimuli). None of the test stimuli produced enhanced skin conductance responses under these conditions. Experiment 2 utilized the same design with only one difference: the test stimuli were presented following a simple stimulus sequence (i.e., repetition of a fixed standard stimulus). In this design enhanced skin conductance responses to the test stimuli were observed in almost all experimental conditions, with an advantage of a late over an early presentation of the test stimulus. Experiment 3 was designed to compare serial position effects of significant and neutral test stimuli. A serial position effect was obtained only for the neutral test stimuli, showing once again an advantage for late presentations. It was suggested that different mechanisms might underlie skin conductance responses to significant stimuli and to novel neutral stimuli.
Rats were trained to bar-press for sucrose solution in the presence of one of two stimulus conditions. On each daily training session, the stimulus during which bar-pressing was reinforced was reversed. The subjects were trained in this Serial Discrimination Reversal procedure until successive acquisitions of the discrimination had stabilized. Drug treatments consisting of saline or 0.25, 1.0, 2.0, 4.0, 6.0 or 8.0 mg/kg of methylphenidate were then administered 20 min prior to the daily training sessions. Acquisition of the discrimination was enhanced by low doses of methylphenidate (1,2, and 4 mg/kg) and attentuated by higher doses (6 and 8 mg/kg).
In a series of previous reports we have described differences in detectability of a target in a background of nontarget patterns as a function of its spatial location. These differences, referred to as a "detectability gradient," have been attributed to target detection accomplished by a serial processing mechanism--a scan. The mathematical model of such a mechanism, developed in the previous report, is equally applicable to a series of attentional shifts or to a perceptual, i.e., a preattentive, mechanism. The present experiments were designed to test the hypothesis that this scan is attentional in nature. The results provide additional evidence for the scanning hypothesis but do not support the view that this scan represents a series of attentional shifts.
This paper reports on a comparison of the two alternative tests of attention in the Mini-Mental State Examination (MMSE), a well-known cognitive screening tool. The two tests, serial subtraction by seven and backwards spelling of the word world, are often used interchangeably. In a large population-based sample, the two tests were found to be weakly associated with each other, with the former test appearing more difficult, although both were strongly associated with educational level. The authors discuss the implications of this finding in clinical and research settings, and make recommendations for more consistent use of the instrument.
The topographical distribution of alpha power reduction was compared in nine unmedicated schizophrenics (predominantly never-treated), 17 medicated schizophrenics, and 15 normal controls. The task involved four procedures: (1) listening to signal sound, (2) listening to digits for memorization, (3) after listening, and (4) listening to digits for recognition. The electroencephalograms (EEGs) during each procedure were analyzed with Fast Fourier Transformation and compared with EEGs at rest. While listening to the digits, medicated schizophrenics showed less alpha power reduction than normal controls and unmedicated schizophrenics. In addition, there were correlations found between the degree of alpha power reduction and medication dose, and score of chronic symptoms. These suggest that patients with different clinical backgrounds have differing cerebral activity.
Phonological short-term memory was investigated in 24 aphasic left brain-damaged patients and in 12 matched controls. Aphasic patients have a reduced auditory and visual immediate memory span and show the standard detrimental effect of phonological similarity on immediate retention only when the stimuli are auditorily presented, while in the control group the effect is present with both auditory and visual input. Most patients have phonological processing deficits, but two patients have an impaired immediate verbal memory in the absence of analysis disorders. These results, in line with most individual case studies of patients with selective deficits of verbal short-term memory, are interpreted with reference to a model distinguishing a phonological short-term store component of memory, to which auditory input has direct and automatic access, and a rehearsal component, that, after phonological recoding, conveys visually presented stimuli to the phonological store. This latter system, that appears to become fully operational later in development, is less resistive to brain damage.
Four experiments used a novel stimulus sequence to compare simultaneous and sequential associations among neutral stimuli in a sensory preconditioning procedure. In Experiments 1, 2, and 4, rats received a sequence of the form AB-B' in which A was simultaneous with B but sequential with B'. Subsequently, either B or B' was conditioned, and the response to A assessed. This procedure matches the context of A's presentation in comparing its sequential association with B' and its simultaneous association with B, something that prior paradigms have neglected. Experiment 3 used an analogous B'-AB procedure to compare simultaneous and backward associations. Experiments 1-3 used a flavor-aversion procedure in which A, B, and B' were flavors and lithium chloride was the reinforcer. Experiment 4 used conditioned suppression with auditory and visual stimuli and shock reinforcer. All four experiments found simultaneous associations between A and B to be substantial. Moreover, in all cases, conditioning of B produced a greater response to A than did conditioning to B', which suggests that simultaneous associations are stronger than are sequential ones when this paradigm is employed.
Two new, long-lasting phenomena involving modality of stimulus presentation are documented. In one series of experiments we investigated effects of modality of presentation on order judgments. Order judgments for auditory words were more accurate than order judgments for visual words at both the beginning and the end of lists, and the auditory advantage increased with the temporal separation of the successive items. A second series of experiments investigated effects of modality on estimates of presentation frequency. Frequency estimates of repeated auditory words exceeded frequency estimates of repeated visual words. The auditory advantage increased with frequency of presentation, and this advantage was not affected by the retention interval. These various effects were taken as support for a temporal coding assumption, that auditory presentation produces a more accurate encoding of time of presentation than does visual presentation.
In five experiments, the effects of organization on implicit memory or priming tests were compared with its effects on the explicit memory tests of free and cued recall. Organization was manipulated by varying list structure (blocked vs. random presentation of categorized items) and by instructions. The results showed that organization had parallel effects on the category-production priming test and free- and cued-recall tests; performance was enhanced by organization on both types of tests. It was also demonstrated that the effect of organization on priming was limited to the category-production test and was not obtained with the word-identification priming test. These results suggest that performance on implicit and explicit memory tests is similarly affected by experimental manipulations when both types of tests rely on conceptually driven processing. In addition, performance on two implicit tests is dissociated when one test relies on conceptually driven processing and the other on data-driven processing.
Self-rated decline in memory relative to estimated abilities at age 60 was investigated in a group of 88 normal elderly subjects age 60 to 90. Self-ratings of storage, retrieval, attention/concentration, remote memory, and depression formed a factor which was orthogonal to objective measures of memory function. Self-rated remote memory was also associated with objective measures of recent/remote memory, and self-rated depression was additionally related to objective measures of attention/concentration.
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A sea lion under water performed virtually without errors on a series of three form-discrimination reversals. Significant training requirements were the combining of a previously well-established size cue preference with the nonpreferred form cue, followed by the gradual reduction of the size cue until it was completely eliminated. Orienting responses reached a peak and then decreased during progressive-dimensional-change training, suggesting critical stages in the transition of attention from the size dimension to the form dimension. Further experimentation revealed that intensive training during these critical stages obviated the need to reduce very gradually the size cue. Without special training sea lions make perseverative errors on a series of form-discrimination reversals. "Emotional" or nontest-oriented behavior was associated only with the occurrence of successive errors.
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