David B. Boles

An upper- and lowercase alphabetic similarity matrix, with derived generation similarity values

A full upper- and lowercase visual similarity matrix is presented for a standard set of computer characters, implemented on the Apple-Psych system. The 2,704 (52×52) letter pairs were rated by 12 subjects each. From the ratings, generation and veridical similarity values are derived, and they are tabled for use in research on mixed-case letter matching. In addition, the results of multidimensional scaling and cluster analyses are presented, which give complementary, simplified descriptions of the data.

What bilateral displays do

Bilateral presentations of stimuli produce asymmetries larger than those of unilateral presentations, an effect that exists across modalities. In the case of visual field differences at least 13 hypotheses of the effect have been proposed, 6 of which suggest that some form of hemispheric interaction is responsible for the bilateral advantage. Previous research has eliminated all 7 noninteraction hypotheses, has supported the class of hemispheric interaction mechanisms, and has ruled out two specific instances of the latter. Here four experiments test the remaining hypotheses. The results support the homolog activation hypothesis, which states that bilateral stimulation by similar stimuli activates homologous areas of the two hemispheres, disrupting communication between the areas. The other hypotheses were eliminated.

Factor analysis and the cerebral hemispheres: Pilot study and parietal functions

Although research on lateral differences has proliferated, attempts to specify fundamental dichotomies of hemispheric processing have yielded less than satisfactory results. The factor analysis of behavioral asymmetries can provide a different approach by helping to identify common functions underlying disparate tasks. It can also provide information on individual differences and interrelationships among functions. Here, the viability of the approach is demonstrated with a small pilot study (N = 29), and with two larger experiments (N = 70 and N = 60) that stress parietal lobe function. Seven lateralized functions were identified: auditory lexical, spatial attentive, spatial positional, spatial quantitative, tactile figural, visual emotional and visual lexical. A range of positive, negative and null correlations was found between functions, contrary to lateralization strength, hemisphericity, and independence models of individual differences in lateralization. However, a pattern of intercorrelations was observed among functions believed to be localized to the perisylvian region (Brodmann areas 22 and 39), which is consistent with the neurodevelopment theory of Geschwind and Galaburda (Cerebral Lateralization Biological Mechanisms, Associations and Pathology, The MIT Press, Cambridge, MA, 1987).

Factor analysis and the cerebral hemispheres: Temporal, occipital and frontal functions

Three experiments are reported that use a number of lateralized tasks believed to draw on processes localized to the temporal, occipital or frontal lobes. Oblique factor analyses of the resultant asymmetries indicate the existence of nine lateralized functions, characterized as auditory lexical, facial figural, facial motive, spatial attentive, spatial positional, spatial quantitative, tactile figural, visual lexical, and visual phonetic in nature. Most functions are uncorrelated, but as in an earlier report (Boles, Neuropsychologia 29, 59-91, 1991), both positive and negative correlations are observed. These outcomes continue to be consistent with neurodevelopmental theory, and inconsistent with lateralization strength, hemisphericity, and independence views of individual differences in lateralization.

Hemispheric differences in global versus local processing: still unclear.

Laterality studies examining the recognition of hierarchical letter forms in normal subjects have had a checkered history. Early ones reported evidence of right hemisphere global and left hemisphere local processing, but later ones found little evidence of lateralized effects. Here three reaction time experiments examine suggestions made in the literature that the asymmetries appear only with small stimulus eccentricities, few experimental trials, or short stimulus exposures. No evidence is found to support a right-hemisphere-global and left-hemisphere-local distinction. However, Experiment 3 reports a shift toward right hemisphere processing of local letters as stimulus duration is curtailed, suggesting right hemisphere involvement when visual conditions are impoverished. These outcomes pose a challenge for clinical reports that differently lateralized cortical lesions have different effects on global and local processing.

Hemispheric differences in the judgment of number

Two manual reaction-time experiments examined visual field differences for the judgment of number. All told, three tasks (recognition/enumeration, magnitude judgment and oddity judgment) were performed on three nonverbal indicators of number (dot clusters, bargraphs and dials) and two verbal indicators (word names of numbers and digits). The results indicated that field differences depended largely on display format, not on the task. Thus, dot clusters, bargraphs and dials all showed a left visual field superiority, while words showed a right visual field superiority. There was no evidence of lateralization for digits.

A simultaneous task comparison of differentiated and undifferentiated hemispheric resource theories.

Multiple resource theory and related principles hold that resources are differentiated both within and between cerebral hemispheres (C. D. Wickens, 1984, 1991, 1992). An opposing view is that each hemisphere constitutes a pool of undifferentiated resources (A. Friedman, M. C. Polson, C. G. Dafoe, & S. J. Gaskill, 1982; M. C. Polson & A. Friedman, 1988). Here the authors compare the theories by using dual-task methodology, drawing on tasks emerging from factor analytic studies of lateralized processes. Selective interference occurs when 2 tasks draw on the same process in the same hemisphere but not otherwise, a conclusion further supported by analyses of difficulty trade-off. Differentiation indeed exists within and between hemispheres, but evidence is found for resources not envisaged in multiple resource theory. The results suggest that orthogonal processes represent orthogonal resources, and a full accounting of them is likely to be needed in any complete multiple resource model.

An experimental comparison of stimulus type, display type, and input variable contributions to visual field asymmetry

Three experiments compare the effects of stimulus type, display type, and input variable contributions to visual field (VF) asymmetry. Stimulus types were words and bar graphs; displays were unilateral and bilateral; and input variables were stimulus eccentricity, duration, luminance, and size. The only influences consistent across studies and with claims in the literature were those of stimulus type and display type. Stimulus type determined the direction of VF asymmetry, while display type determined its magnitude. The results suggest that both influences should be accounted for in research using VF asymmetry as an index of hemispheric differences, while input variables can largely be ignored.

The Effect of Symbols on Warning Compliance

The present study investigated whether different warning designs, specifically those with symbols, affect compliance rates. Five conditions were tested: a verbal warning, a pictographs warning with a circle enclosing each graphic, a pictographs warning with a triangle on its vertex enclosing each graphic, a warning with both words and pictographs (triangular enclosures), and a control (no warning). Participants performed a chemistry laboratory task using a set of instructions that contained one of the five conditions. The warnings instructed them to wear safety goggles, mask and gloves. All four warning conditions had significantly greater compliance than the no-warning condition. The highest rate of compliance occurred with the verbal plus pictographs condition, although it did not differ significantly from the verbal condition. A significant main effect was found for the “presence of pictographs” variable, suggesting that the addition of pictographs to a verbal warning will increase compliance rates. The unexpected finding that the pictographs warning with triangular enclosures had significantly lower compliance means than the verbal warning may be due to the different types of message modes or design criteria used. The enclosure shape made no difference in compliance rates, despite research that indicates that unstable shapes are preferred as warning enclosures. The results suggest the importance of conducting behavioral studies rather than relying on preference data.

Display formatting in information integration and nonintegration tasks

The impact of various formats used in the design of visual displays was investigated in two reaction-time (RT) experiments. Analog, digital, and verbal formats were employed with numerical judgment tasks requiring either the integration or non integration of display elements. As predicted by multiple resource theory, the dual task (nonintegration) benefited from a mixed-format display. Integration tasks, however, revealed a contrasting benefit of pure-format displays. Generally speaking, analog indicators were responded to more quickly than were digital or verbal indicators. Three guidelines for display design are suggested.