Locus of the effect of a distinguishing feature in a memory search task

Subjects memorized one to four 8- or 16-sided random forms in a memory search task. The positive set forms ("yes" response) differed in number of sides from the negative set forms ("no" response) for the different set (DS) group, but this distinguishing feature was not available to the same set (SS) group. Mean reaction time increased as a linear function of log(2) of the positive set size for both groups, but the increase was greater for the SS than the DS group, suggesting that memory search rather than an encoding stage of information processing was influenced by the availability of a distinguishing feature. In a transfer task which followed, new forms were introduced in which the positive and negative set forms differed in number of sides for both groups. In this task, the two groups did not differ in memory search, but in encoding. It was proposed that (a) availability of a distinguishing feature influences search time because the information specifying the number of sides of the set of memorized forms can be used to influence the speed with which individual forms are examined in memory; (b) previous experience with a distinguishing feature influences encoding because the DS group had learned to extract the information specifying the set of memorized forms (not the information specifying individual forms) more efficiently than the SS group.     

Descriptive axioms for common factor theory,image theory and component theory

Through an extension of work by Guttman, common factor theory, image theory, and component theory are derived from distinct minimum subsets of assumptions chosen out of a set of five possible assumptions. It is thence shown that the problem of indeterminacy of factor scores in the common factor model is precisely reflected in the problem of the non-orthogonality of anti-images. Indeed, image scores are determinate for the same reason that the usual estimates of factor scores are determinate, and image scores cannot be used as though they were factor scores for the same reason that factor score estimates cannot be used as though they were factor scores.     

On mathematical illusions

A criticism of Walker’s (1973) paper on the grounds that its physiological premises lack support, that it misrepresents the theoretical position of Blakemore, Carpenter, and Georgeson (1970), and that its theory is contradicted by existing evidence.     

Methylphenidate increases selectivity of visual scanning in children referred for hyperactivity

Visual scanning patterns were investigated in 32 children referred for symptoms of hyperactivity in a doubleblind crossover comparison of methylphenidate and placebo treatments. Total errors, response latency, and visual fixations were recorded as the child scanned computer-generated visual matching-to-sample problems. Results indicated that the number of fixations on the standard stimulus in the matching task was significantly larger in the methylphenidate state. Drug treatment also resulted in a significant increase in the number of systematic comparisons between the standard and the variants in the task. However, the increased selectivity of attention to the standard stimulus was not accompanied by a reduction of total errors. It was suggested that the stimulant drug may increase attentional selectivity even when such a shift fails to produce improvement in task performance.This research is based in part upon a master's thesis completed by the first author in the department of Psychology, University of Guelph. The authors are indebted to Dean H. Owen for providing the random polygons used in the experiment. The research was supported by grants from the Ontario Mental Health Foundation and the Medical Research Council of Canada to James M. Swanson.     

Developmental verbal control of behavior: Implications for self-instructional training

Kindergarten, first-grade, and second-grade children (5, 6, and 7 years of age, respectively) performed a Luria-type verbal control task in which motor responses are initiated to positive stimuli and inhibited to negative stimuli. The task was performed by motor responding only and verbal self-directed motor responding, with these conditions reversed in sequence for one half of each grade group. Although motor responding and verbal-motor responding by the two younger groups were generally poor, their performance equalled that of the second graders when the verbalizing condition followed the silent, motor-only condition. For these children, verbalizing appeared to constitute a second task which interfered with motor responding. Prior practice on motor-only responding, however, facilitated subsequent, concurrent performance of the two tasks. No interference or practice effects were found for the second graders. The results suggested that self-instructional training programs are likely to be successful when adequate verbal-motor coordination can be assumed or when the motor response is within the child's repertoire.     

The effects of lexical and semantic information on same-different visual comparison of words

Previous research has indicated that phonemic and orthographic factors cannot account for the fact that words (clear/clear) are responded to more rapidly than orthographically legal nonwords (creal/creal) in a same-different visual comparison task. However, the role of semantic and lexical factors is less certain. The effects of semantic similarity on both same and different judgments were evaluated in several experiments. In the first experiment, subjects were not any slower on semantically related (rang/rung) than on unrelated (rang/rank) different judgments even with a 3,000-msec interval between the first and second word. In Experiment 2, subjects based their judgments on whether or not the first letter of each word was visually identical. Same judgments were not any faster for semantically related than unrelated items even though other evidence indicated that subjects were processing the whole word and not just the first letter. Experiment 3 showed that the word/orthographically legal nonword difference could be replicated with the first-letter visual comparison task employed in Experiment 2. These and related results were discussed with reference to the idea that the word/orthographically legal nonword difference is due to the facilitating effects of a lexical entry upon the encoding, but not the comparison of an item.     

Ambiguous musical figures and auditory streaming

Three experiments with musicians and nonmusicians (N=338) explored variations of Deutsch’s musical scale illusion. Conditions under which the illusion occurs were elucidated and data obtained which supported Bregman’s suggestion that auditory streaming results from a competition among alternative perceptual organizations. In nExperiment 1, a series of studies showed that it is more difficult to induce the scale illusion than might be expected if it is accepted that an illusion will be present for most observers despite minor changes in stimuli and experimental conditions, The stimulus sequence seems better described as an ambiguous figure. Having discovered conditions under which the scale illusion could be reliably induced, Experiments 2 and 3 manipulated additional properties of the stimulus (timbre, loudness, and tune) to provide cues to streaming other than pitch and location. The data showed that streaming of this sequence can be altered by these properties, supporting the notion of a general parsing mechanism which follows general gestalt principles and allows streaming by many stimulus dimensions. Finally, suggestions are made as to how this mechanism might operate.     

Some results on proper eigenvalues and eigenvectors with applications to scaling

Conditions are given under which the stationary points and values of a ratio of quadratic forms in two singular matrices can be obtained by a series of simple matrix operations. It is shown that two classes of optimal weighting problems, based respectively on the grouping of variables and on the grouping of observations, satisfy these conditions. The classical treatment of optimal scaling of forced-choice multicategory data is extended for these cases. It is shown that previously suggested methods based on reparameterization will work only under very special conditions.