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Biomedical subjects

D B Boles

Publications and source records attributed to D B Boles.

At least 19 recordsLinked to original sources
PubMed1998

Relationships among multiple task asymmetries. I. A critical review.

Previous multiple-task experiments examining relationships among lateral difference measures have been interpreted as supporting (a) both global and local relationships or (b) local relationships only. The evidence from principle components, correlational, and factor analytic approaches is reviewed with the aim of reconciling the literature. Although a principle component has been reported to which all asymmetries correlate positively, it may not reflect existing null and negative correlations between pairs of measures. All three literatures make clear that such correlations exist, calling into question the reality of a global relationship. In contrast, all three approaches find evidence supporting the reality of local relationships. Factor analytic approaches most fully develop local relationships and permit interpretation in terms of hemispheric processes, but they need to (a) use larger sample sizes, (b) prescreen measures for reliability, and (c) make publicly available the underlying correlational matrices.

Auditory Perception↗
PubMed1998

Relationships among multiple task asymmetries. II. A large-sample factor analysis.

Samples from published and unpublished factor analytic studies of multiple task asymmetry are combined to produce a large-sample factor analysis of 10 measures, prescreened for significant asymmetry and acceptable reliability, from 9 lateralized tasks. A full correlational matrix is presented, with task pairings having sample sizes ranging from 103 to 479 (mean N = 290). Both significant positive and significant negative correlations between measures are found. Extraction and oblique rotation of five factors fails to reveal any evidence of a global relationship among lateral difference measures, and principal-components analysis likewise fails to reveal a component to which all measures correlate positively. However, evidence for local structure is found. Results are interpreted in terms of dissociable hemispheric processes, and consideration is given of the possible existence of modality-specific characteristic perceptual asymmetry and of single versus multiple determination of lateral differences.

Adult↗
PubMed1998

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.

Brain↗
PubMed1996

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.

Brain↗
PubMed1996

Factor analysis and the cerebral hemispheres: "unlocalized" functions.

Previous factor analyses have employed lateralized task tapping processes (functions) whose localizations are thought to be known at the level of the cerebral lobe or finer. Here nine tasks are introduced to factor analysis whose underlying processes have unknown localization. A new function identified as auditory emotional is found to be independent of asymmetry in a visual emotion judgment task, suggesting that lateralized emotion judgments depend on modality specific processes. A second new function identified as visual temporal is found to be independent of asymmetries in visual language recognition, posing constraints on theories that link lateralized language processes to processes dealing with temporal sequencing. Another important finding is that the recognition of dichotic syllables relies on a previously identified process, indicating that the process is better labelled auditory linguistic than auditory lexical and suggesting that lexical status may be irrelevant to auditory language asymmetries. Also, a word naming task is found to produce visual field asymmetry because of a stimulus encoding (visual lexical) process, with no clear evidence found of influence from asymmetric response processes. Taken together, the full set of lateralized processes appear to show high degrees of modality specificity and mutual independence (modularity).

Adolescent↗
PubMed1996

Correlated auditory asymmetries in lexical and nonlexical tasks.

Two experiments address the question of whether different auditory verbal tasks produce correlated asymmetries. The first shows that ear asymmetries from dichotic word and syllable tasks do in fact correlate, but not to asymmetry from a visual face processing task. The second replicates the correlation between word and syllable asymmetries and shows that this significant relationship does not extend to another dichotic task involving the recognition of emotional tones of voice. The results are viewed as consistent with a left-hemisphere based "auditory linguistic" process involved in recognizing both lexical and nonlexical materials.

Adult↗
PubMed1994

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.

Adult↗
PubMed1993

Visual field effects of classical migraine.

Although classical migraine is known to produce lateralized sensory disturbances (e.g., visual "fortification" structures), its effect on higher order processes is unknown. Here four lateralized visual tasks were repeatedly presented to a single subject (the author) over a 2 1/2-year span, during both classical migraine attacks and headache-free periods. Attacks varied as to inferred hemispheric locus. All four tasks ("words," "typing," "bar graphs," and "locations") produced significant or marginally significant visual field (VF) by condition interactions, results generally consistent with a phasic impairment of function in the migrainous hemisphere. A content analysis of notes made during the attacks suggests that among other symptoms, alphabetic indistinctiveness and spatial disturbances are characteristics of left and right hemisphere attacks, respectively. Aspects of the results argue against any major influence of demand characteristics.

Adult↗
PubMed1992

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.

Arousal↗
PubMed1992

Fast visual generation: its nature and chronometrics.

The fast-generation model for the matching of mixed-case letter pairs (e.g., Aa, Ab) states that one or both members of a pair activate visual representations in memory of the opposite case, supporting "same" or "different" responses through crossmatching to representations of the pair members themselves. Here the reaction time and error results of three experiments using simultaneous matches support a specific variant of the model in which generation proceeds from the uppercase letter. Furthermore, a manipulation of stimulus onset asynchrony in a fourth experiment using near-simultaneous matches indicates that fast generation produces a visual representation that occurs within 67 msec of initiation and that decays within 200 msec. A fifth experiment contrasts simultaneous and successive matches and in the case of successive matches finds evidence in support of a regeneration process acting after an initial decay. Models of mixed-case matching that are based on the phonetic representation of letter names, or on abstract-letter identities, completely fail to account for the results. Fast generation is distinguishable from slow generation in that it shows fast (vs. slow) dynamics, rapid decay (vs. maintainability), no imagery (vs. imagery), and (probably) automatic (vs. controlled) processing.

Attention↗
PubMed1991

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).

Adult↗
PubMed1990

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.

Arousal↗
PubMed1989

Do visual field asymmetries intercorrelate?

Lateralized word and bargraph recognition tasks were presented to 22 right-handed and 15 left-handed subjects. The correlation between the opposite reaction time asymmetries for the tasks was significant, and indicated that individual subjects generally showed strong lateralization for one task and weak lateralization for the other. The results are viewed as inconsistent with models of individual differences in hemispheric function that stress strong hemisphericity, lateralization strength, or independent functions. However, they are consistent with a model stressing weak hemisphericity. Also potentially consistent with the results is the neurodevelopmental theory of Geschwind and Galaburda (Cerebral Lateralization: Biological Mechanisms, Associations and Pathology, MIT Press, Cambridge, Massachusetts, 1987), if it is assumed that the lateralized functions reflected by the tasks are subserved by homologous anatomical areas. Compared to right-handers, left-handers tended to produce a smaller correlation between the tasks, as well as weaker hand preferences, and smaller and less reliable field asymmetries.

Adult↗
PubMed1989

Word attributes and lateralization revisited: implications for dual coding and discrete versus continuous processing.

Three attributes of words are their imageability, concreteness, and familiarity. From a literature review and several experiments, I previously concluded (Boles, 1983a) that only familiarity affects the overall near-threshold recognition of words, and that none of the attributes affects right-visual-field superiority for word recognition. Here these conclusions are modified by two experiments demonstrating a critical mediating influence of intentional versus incidental memory instructions. In Experiment 1, subjects were instructed to remember the words they were shown, for subsequent recall. The results showed effects of both imageability and familiarity on overall recognition, as well as an effect of imageability on lateralization. In Experiment 2, word-memory instructions were deleted and the results essentially reinstated the findings of Boles (1983a). It is concluded that right-hemisphere imagery processes can participate in word recognition under intentional memory instructions. Within the dual coding theory (Paivio, 1971), the results argue that both discrete and continuous processing modes are available, that the modes can be used strategically, and that continuous processing can occur prior to response stages.

Adult↗
PubMed1987

Reaction time asymmetry through bilateral versus unilateral stimulus presentation.

Previous research indicates that bilateral stimulation of the visual fields results in larger asymmetry than unilateral stimulation. However, the research has largely been limited to percentage correct studies. Here, three experiments employ reaction time (RT) measures, and show that the bilateral advantage generalizes to RT, and across spatial and verbal stimulus materials (bargraphs, letters, and words). Visual field differences average about six times larger with bilateral than with unilateral presentation. Beyond promising increased power to detect hemispheric differences, the results argue against structural and attentional models of behavioral asymmetry and support a dynamic (hemispheric interaction) model.

Attention↗
PubMed1986

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.

Functional Laterality↗
PubMed1985

The effects of display and report order asymmetries on lateralized word recognition.

Word recognition typically is better or faster in the right visual field than in the left visual field, an effect that often interacts with the handedness of subjects or the phonetic characteristics of the language employed. While these findings suggest a hemispheric locus, it is possible that the field difference is confounded with display or report order asymmetries. Here two experiments manipulate word orientation (horizontal vs. vertical), letter symmetry, and report order variables, and they demonstrate a generalized right field superiority that fails to interact with other factors. Since the superiority appears even when all apparent artifactual asymmetries are eliminated, the findings support a hemispheric interpretation.

Dominance, Cerebral↗