Selective attention in the speeded classification and comparison of multidimensional stimuli

Selective attention was studied when subjects were required to make either speeded classifications of single stimuli or comparisons of pairs of multidimensional stimuli. Experiment 1 established that subjects were able to attend selectively to form when the irrelevant dimension of size or shading varied in a speeded-classification (card-sorting) task. Experiment 2 confirmed this finding in a discrete-trials task. However, subjects werenot able to filter out irrelevant dimensional disparity in a comparably designed simultaneous-comparison (i.e., “same”-“different”) task. Mean “same” reaction time increased monotonically with increases in disparity between the two stimuli on the irrelevant dimension. Experiment 3 also revealed a monotonie increase in “same” RT as a function of irrelevant disparity in a successive-comparison task. These results were discussed in terms of a normalization model proposed by Dixon and Just (1978) in which it is assumed that a subject equates the two stimuli on the irrelevant dimension before deciding that they are the same along the relevant dimension. It was concluded that: (1) although subjects can efficiently filter out irrelevant disparity in a speeded-classification task, interference due to irrelevant disparity is obtained in the comparison tasks, (2) a common process such as normalization does not necessarily underlie performance in the speeded-classification and comparison tasks, (3) the ability to attend selectively to a stimulus dimension may be task determined as well as stimulus determined, and (4) contrary to the Dixon and Just proposal, normalization of irrelevant disparity occurs in a comparison task, even when the relevant dimension is represented as a separate encoding feature.     

Verbal and nonverbal recognition memory in aphasic and nonaphasic stroke patients

The ability to retain lists of verbal and nonverbalizable items across recurrent recognition tasks was tested in three groups: (1) stroke patients with a left-brain lesion and aphasia, (2) stroke patients with a right-brain lesion and left hemiplegia, and (3) nonneurologically impaired outpatients. As determined with signal detection measures, aphasics were deficient in discriminating words that were to be remembered from those that were not; their recognition of nonverbal visual (geometric art) or auditory (bird calls) patterns, however, was unimpaired. Left hemiplegics showed the opposite pattern. After a long-term interval (<10 min), correct recognition of words was diminished in all groups whereas recognition of visual patterns increased. Both groups of stroke patients adopted material-specific decision criteria which in part accounted for the dissociation of verbal and nonverbal recognition memory by laterality of lesion. Item analysis indicated that aphasics' verbal memory difficulties were affected by acoustic-semantic confusion of list words.     

The effects of distributed training on retention of operant conditioning in human infants

Long-term retention of operant footkicking acquired in the mobile conjugate reinforcement paradigm was assessed as a function of the distribution of training time. In the first study, 3-month-old infants were trained for either one 18-min session or for two 9-min or three 6-min sessions separated by 24-hr intervals. All infants exhibited retention during a test administered immediately after training, but only those trained in a single session continued to perform the conditioned response during cued-recall tests 7 or 14 days later. Infants trained in three sessions showed no evidence of remembering the contingency even after a week. A warm-up decrement, seen in the day-to-day performance of infants in the distributed conditions, was eliminated in the second study by the interpolation of a nonreinforcement period at the outset of daily sessions. This procedure also enhanced long-term retention such that infants trained in three 6-min session now remembered the contingency for 14 days and did not differ from infants who had received a single 18-min session. Whether distributed training facilitates or impairs long-term retention appears to depend on the opportunity for infants to acquire a sufficient number (or kind) of effective retrieval cues during original learning.     

Personality diagnostic questionnaire-revised (PDQ-R) personality disorder scores and negative life events independently predict changes in hopkins symptom checklist (SCL-90) Psychopathology Scores

The present study employed a prospective design to investigate whether Personality Diagnostic Questionnaire—Revised (PDQ-R) scores and/or Hassles Scale—Revised (HS-R) scores predict changes in Axis I psychopathology levels over 1 month, in a nonclinical sample of young adults. The PDQ-R, HS-R, and Hopkins Symptom Checklist (SCL-90) were administered to a mixed-sex sample of 100 undergraduate students on two occasions separated by 1 month. Hierarchical multiple regression analyses indicated that (1) time 1 PDQ-R composite scores predicted changes in scores on 11 SLC-90 scales; (2) time 1 PDQ-R impairment/distress index scores predicted changes in SCL-90 general symptom index scores; (3) only one of the individual PDQ-R personality disorder subscales—the schizotypal personality disorder subscale—predicted changes in SCL-90 general symptom index scores; (4) HS-R scores predicted changes in scores on 9 SCL-90 scales; and (5) in only 3 of the 27 analyses conducted did the statistical interaction between PDQ-R and HS-R scores predict changes in SCL-90 scores. These findings indicate that personality disorder symptomatology and negative life events may independently predict changes in Axis I psychopathology levels and, thus, support the continued inclusion of Axis II and Axis IV in future versions of the Diagnostic and Statistical Manual of Mental Disorders.     

The philosophical works of wilfrid sellars

Expanded bibliography fromThe Metaphysics of Epistemology. Lectures by Wilfrid Sellars, edited by Pedro V. Amaral, Ridgeview Publ. Co., Atascadero, Calif. 1989, pp. 343–353, with addenda and corrigeda.