Lateral preferences and writing hand posture in left-handers: A reply to Levy

In reply to the commentary from J. Levy about a recent article of ours (A. Searleman, C. Porac, & S. Coren, 1984, Brain and Cognition, 3, 86–93), we find that she has shifted the level of analysis from between-sex comparisons (as demanded by our original hypothesis) to within-sex comparisons. Since she is addressing a different set of questions, we therefore find no compelling reasons to alter any of our conclusions or the confidence that we have in these conclusions.     

Spatial versus tree representations of proximity data

In this paper we investigated two of the most common representations of proximities, two-dimensional euclidean planes and additive trees. Our purpose was to develop guidelines for comparing these representations, and to discover properties that could help diagnose which representation is more appropriate for a given set of data. In a simulation study, artificial data generated either by a plane or by a tree were scaled using procedures for fitting either a plane (KYST) or a tree (ADDTREE). As expected, the appropriate model fit the data better than the inappropriate model for all noise levels. Furthermore, the two models were roughly comparable: for all noise levels, KYST accounted for plane data about as well as ADDTREE accounted for tree data. Two properties of the data proved useful in distinguishing between the models: the skewness of the distribution of distances, and the proportion of elongated triangles, which measures departures from the ultrametric inequality, Applications of KYST and ADDTREE to some twenty sets of real data, collected by other investigators, showed that most of these data could be classified clearly as favoring either a tree or a two-dimensional representation.A portable PASCAL program implementing the Sattath and Tversky [1977] ADDTREE algorithm is available from J. Corter, Department of Psychology, Stanford University, Stanford, California 94305.     

Choice vs. Preference: The Effects of Choice and No Choice of Preferred and Non Preferred Spelling Tasks on the Academic Behavior of Students with Disabilities

The effects of choice and no choice of preferred and non preferred instructional activities on the academic behavior of 3 students with disabilities were investigated. Participant preferences for spelling tasks were assessed and an ABCDEF design was used to examine choice and preference within 6 experimental conditions: a) choice of preferred tasks, b) choice of non preferred tasks, c) no choice of preferred tasks, d) no choice of non preferred tasks, e) no choice of preferred tasks (yoked-control), and f) no choice of non preferred tasks (yoked-control). Results indicate that all 3 participants had higher levels of task engagement when working with preferred tasks, regardless of a choice or no choice format. The findings from this investigation contribute to the growing body of research that focuses on developing interventions that are responsive to individual student preferences.     

The assessment of components involved in illusion formation using a long-term decrement procedure

Available evidence seems to indicate that illusion decrement represents reorganization of cognitive components involved in visual-geometric illusions. Observers viewed one of the two forms of the Mueller-Lyer illusion, containing differential opportunities for peripheral structural interactions, for a 10-min test session on each of 5 successive days. The magnitude of the distortion decreased to a different asymptotic level in each of the two configurations with the form, with more opportunity for structural interactions showing the higher asymptote. Thus, this asymptote probably represents the structural or physiological contribution to the illusory distortion.     

The fading of stabilized images: Eye movements and information processing

Two experiments are reported which indicate that neural and photochemical satiation processes are inadequate to explain the fading of the stabilized retinal image. When eye movements are attempted over the stimulus, fading occurs more rapidly, indicating an information processing component in the disappearance of the image.     

Recall of common and distinctive features of verbal and pictorial stimuli

Subjects first rated similarity of verbal and of pictorial stimuli. The same pairs of stimuli were presented again, without one common component and one distinctive component. Subjects were asked to recall the missing components and identify them as common or distinctive. The results show that components encoded as common are recalled relatively better than components encoded as distinctive, and the difference in recall is significantly greater in verbal than in pictorial stimuli.     

Visual angle and the word superiority effect

Two experiments are reported in which a word superiority effect is obtained under conditions where a fixed set of alternatives are employed with positional certainty as to the critical letter, trial type (word or nonword) is mixed, and the subject is told to fixate the position of the critical letter. A third experiment employed the same methodology except for the fact that the stimuli subtended a larger retinal angle. No word superiority effect was observed in the third experiment. It is suggested that the visual angle of the stimulus display is a crucial factor in experiments on the word superiority effect.     

Altering Mueller-Lyer illusion magnitude using figural additions at the wing-shaft intersections

The Mueller-Lyer (ML) illusion has been used to study the way in which perceived length is affected by processes of information extraction when a visual target of interest (the ML shaft) is surrounded by other nontarget figural elements (inward-or outward-turning wings). It is argued that the perception of length is computed in terms of the center of gravity or centroid of figural elements at the wing-shaft intersection. The outward-turning wings shift the computational centroid away from the shaft end, giving rise to an erroneous overestimation of shaft length, while the inward-turning wings have the opposite effect. In three experiments, we observed that figural changes, which theoretically shifted the center of gravity of figural elements at the wing-shaft intersection, also increased or decreased the magnitude of the ML illusion.