The face is the thing: Faces, not emotions, are responsible for chimeric perceptual asymmetry.

We used factor analysis to examine relationships among tasks that have previously shown right hemispheric processing asymmetries. We were interested in whether processing emotion displayed by a face constitutes a distinct perceptual process from processing other facial characteristics. Interest in this topic arose after Boles [ 1991 . Factor analysis and the cerebral hemispheres: Pilot study and parietal functions. Neuropsychologia, 29 ( 1 ), 59 - 91 ] found evidence of a common process underlying face processing and then Boles [ 1992 . Factor analysis and the cerebral hemispheres: Temporal, occipital and frontal functions. Neuropsychologia, 30 ( 11 ), 963 - 988 ] found evidence of a distinct process for the processing of the facial emotion. We used seven tasks that measured both face and non-face perception. Analysis of the asymmetries revealed measures from the five face tasks resulted in a single factor, thus failing to support the hypothesis that emotional face perception would involve a separate process from non-emotional face perception. A second factor revealed a separate process underlying enumeration, and a third factor revealed yet another process underlying line bisection. The results indicate that perceiving facial emotion results in right hemisphere processing, and faces as a whole are responsible for such processing.

Viewing the workload of vigilance through the lenses of the NASA-TLX and the MRQ.

OBJECTIVE: The aim of this study was to compare the effectiveness of a new index of perceived mental workload, the Multiple Resource Questionnaire (MRQ), with the standard measure of workload used in the study of vigilance, the NASA Task Load Index (NASA-TLX). BACKGROUND: The NASA-TLX has been used extensively to demonstrate that vigilance tasks impose a high level of workload on observers. However, this instrument does not specify the information-processing resources needed for task performance. The MRQ offers a tool to measure the workload associated with vigilance assignments in which such resources can be identified. METHOD: Two experiments were performed in which factors known to influence task demand were varied. Included were the detection of stimulus presence or absence, detecting critical signals by means of successive-type (absolute judgment) and simultaneous-type (comparative judgment) discriminations, and operating under multitask vs. single-task conditions. RESULTS: The MRQ paralleled the NASA-TLX in showing that vigilance tasks generally induce high levels of workload and that workload scores are greater in detecting stimulus absence than presence and in making successive as compared to simultaneous-type discriminations. Additionally, the MRQ was more effective than the NASA-TLX in reflecting higher workload in the context of multitask than in single-task conditions. The resource profiles obtained with MRQ fit well with the nature of the vigilance tasks employed, testifying to the scale's content validity. CONCLUSION: The MRQ may be a meaningful addition to the NASA-TLX for measuring the workload of vigilance assignments. APPLICATION: By uncovering knowledge representation associated with different tasks, the MRQ may aid in designing operational vigilance displays.

Preschool child and adult lateralisation and performance in emotion and language tasks.

A total of 34 undergraduate students from the University of Alabama and 34 preschool children completed measures assessing lateralisation and competency in emotion and language processing in order to examine the developmental time course of the underlying lateralised processes. Results indicate different developmental time courses for lateralisation in dichotic words and chimeric faces tasks, and provide some support for the developmental models of Boles, Barth, and Merrill (2008) concerning the relationship between lateralisation and performance.

Laterality and sex differences in tactile detection and two-point thresholds modified by body surface area and body fat ratio.

Tactile detection and two-point discrimination tests are commonly used in neurological examinations. However, questions remain about the influence of both body and patient characteristics on test thresholds. The left side of the body has sometimes been reported more tactilely sensitive than the right, and females are said to be more sensitive than males. We measured tactile detection and two-point discrimination thresholds on the finger, palm, and forehead of a large sample of young adults (N=171), examining laterality and sex differences, and the effects of body surface area (BSA) and body fat ratio (BFR). In tactile detection, there were no effects of laterality, BSA, or BFR, although females had lower thresholds than males. In two-point discrimination, there was an effect of laterality, with lower thresholds on the left side. This probably reflects hemispheric spatial processing differences. A significant BFR effect implies that subcutaneous fat affects skin deformation, but there were no effects of sex or BSA. The two-point discrimination findings differ in several respects from recent findings using grating orientation discriminations. A small positive correlation between the tasks, falling far short of test-retest reliabilities, indicates that they use largely disjoint but partially overlapping processes.

Socioeconomic status, a forgotten variable in lateralization development.

Socioeconomic status (SES), a variable combining income, education, and occupation, is correlated with a variety of social health outcomes including school dropout rates, early parenthood, delinquency, and mental illness. Several studies conducted in the 1970s and 1980s largely failed to report a relationship between SES and hemispheric asymmetry as measured by lateral differences in dichotic listening, tactile dot enumeration, and visual emotion and word recognition. However, none of the studies used asymmetry measures correcting for both ceiling and floor effects in accuracy, raising the question of whether lower and higher SES groups were comparable. Here the published data are reanalyzed using a laterality coefficient that corrects for such effects. The results are consistent across studies in revealing reduced lateralization in lower SES groups. Developmentally, this finding is consistent with either maturation delay or reduced functional specialization, or both. Suggestions are made for further research that include the use of behavioral asymmetry measures to screen tasks for structural and functional brain imaging.

"Does degree of asymmetry relate to performance?" A critical review.

In a recent paper, Chiarello, Welcome, Halderman, and Leonard (2009) reported positive correlations between word-related visual field asymmetries and reading performance. They argued that strong word processing lateralization represents a more optimal brain organization for reading acquisition. Their empirical results contrasted sharply with those of another such large-scale study, by Boles, Barth, and Merrill (2008). We reported negative correlations between asymmetry and performance when both were measured using the same visual lexical tasks. Most recently, within-task negative correlations were also reported by Hirnstein, Leask, Rose, and Hausmann (2010). Here two major differences between studies are explored. Task purity refers to the influence of the same mental processes on both the asymmetry and performance measures, and is arguably maximal in studies measuring both within the same task. The other difference concerns the measurement of asymmetry. Linear corrections for ceiling and floor effects were used by Chiarello et al. and Hirnstein et al., while we used a more appropriate nonlinear one. Their results are difficult to interpret for those reasons. The operation of a third variable to which both asymmetry and performance are positively correlated could also be a factor in the Chiarello et al. findings. The Boles et al. findings reflect a negative correlation between an asymmetric visual lexical process and performance measured within the same task.

A preliminary study of lateralized processing in attention-deficit/hyperactivity disorder.

Attention-deficit/hyperactivity disorder (ADHD) is associated with deficits in spatial and sustained attention processes normally linked to the right parietal and frontal lobes. However, data on lateralization changes in attention processes are sparse. Little research has addressed whether the problems may reflect a more widespread lateralization disorder or whether there are lateralization changes over time. To address these issues, the authors examined several tasks, each using a lateralized process largely localized to a particular lobe and 2 age ranges (11-14 and 18-26 years) of unmedicated ADHD participants and control participants. ADHD children bisected lines significantly more rightward compared with control children, indicating an altered spatial attention process normally localized to the right parietal lobe. This problem was absent in young adults, suggesting a developmental resolution. The authors observed sustained attention decrements at both ages appearing earlier in the left hemisphere during a vigil. Finally, in these preliminary data, ADHD-related problems appeared specific to attention processes.

Asymmetry and performance: toward a neurodevelopmental theory.

Hemispheric asymmetry implies the existence of developmental influences that affect one hemisphere more than the other. However, those influences are poorly understood. One simple view is that asymmetry may exist because of a relationship between a mental process' degree of lateralization and how well it functions. Data scaling issues have largely prevented such investigations, but it is shown that scaling effects are minimized after correction for ceiling and floor effects. After correction, lateralization-performance correlations are pervasive. However, while some correlations are positive, others are negative, with the direction depending on the underlying lateralized process. Two hypotheses are proposed that can account for these relationships by pointing either to individual differences in maturation of the corpus callosum or to developmental limits encountered at different ages of childhood. Their investigation should contribute toward a neurodevelopmental theory of hemispheric asymmetry.

What dot clusters and bar graphs reveal: subitizing is fast counting and subtraction.

In two studies, we found that dot enumeration tasks resulted in shallow-sloped response time (RT) functions for displays of 1-4 dots and steep-sloped functions for displays of 5-8 dots, replicating results implicating subitizing and counting processes for low and high ranges of dots, respectively. Extracting number from a specific type of bar graph within the same numerical range produced a shallow-sloped but scallop-shaped RT function. Factor analysis confirmed two independent subranges for dots, but all bar graph values defined a unitary factor. Significantly, factor scores and asymmetries both showed correlations of bar graph recognition to dot subitizing but not to dot counting, strongly suggesting that subitizing was used in both enumeration of low numbers of dots and bar graph recognition. According to these results, subitizing appears to be a nonverbal process operating flexibly in either additive or subtractive fashion on analog quantities having spatial extent, a conclusion consistent with a fast-counting model of subitizing but not with other models of the subitizing process.

Fixation and attention control in lateralised target detection and free recall with words.

The purpose of the present study was to test the hypothesis that lateralised target detection in the visual modality would produce results similar in magnitude, reliability, and validity to those obtained in the auditory modality with an analogue task. Thus, it was expected that it would produce laterality effects that are larger, more reliable, and more valid than those obtained in a free recall task. The claim that target detection provides its own attention control also led to the hypothesis that the magnitude of laterality effects should be affected by fixation control in free recall but not target detection. A total of 349 right-handed participants completed a word recognition task with either free recall or target detection with or without fixation control. Only the finding that free recall was generally more reliable than target detection went contrary to the hypotheses. This finding is interpreted as reflecting a consistent attentional bias that stems from task requirements. In general, the results suggest that target detection without fixation control has much potential as a measure of perceptual asymmetries in the visual modality.

Predicting dual-task performance with the Multiple Resources Questionnaire (MRQ).

OBJECTIVE: The objective was to assess the validity of the Multiple Resources Questionnaire (MRQ) in predicting dual-task interference. BACKGROUND: Subjective workload measures such as the Subjective Workload Assessment Technique (SWAT) and NASA Task Load Index are sensitive to single-task parameters and dual-task loads but have not attempted to measure workload in particular mental processes. An alternative is the MRQ. METHOD: In Experiment 1, participants completed simple laboratory tasks and the MRQ after each. Interference between tasks was then correlated to three different task similarity metrics: profile similarity, based on r(2) between ratings; overlap similarity, based on summed minima; and overall demand, based on summed ratings. Experiment 2 used similar methods but more complex computer-based games. RESULTS: In Experiment 1 the MRQ moderately predicted interference (r = +.37), with no significant difference between metrics. In Experiment 2 the metric effect was significant, with overlap similarity excelling in predicting interference (r = +.83). Mean ratings showed high diagnosticity in identifying specific mental processing bottlenecks. CONCLUSION: The MRQ shows considerable promise as a cognitive-process-sensitive workload measure. APPLICATION: Potential applications of the MRQ include the identification of dual-processing bottlenecks as well as process overloads in single tasks, preparatory to redesign in areas such as air traffic management, advanced flight displays, and medical imaging.

A large-sample study of sex differences in functional cerebral lateralization.

For practitioners, the importance of sex differences in lateralization lies in their potential prediction of susceptibility to and recovery from hemispheric damage. However, previous literature reviews suggest that sex accounts for only 0.1-1% of the variance in asymmetry scores. Here a large-sample, single-laboratory approach uses tasks requiring the recognition of bargraphs, dichotic words, facial emotions, locations, and visual words, and visual line bisection, each sensitive to lateralization of a separate mental module. The results agree with previous reviews, with sex accounting for a maximum of 0.9% and an average of 0.09% of the variance, suggesting that sex has little predictive clinical utility. However, the strength of relationship between sex and laterality depends on the nature of the lateralized task, presumably because of differences between tasks in underlying lateralized modules.

Lateralized spatial processes and their lexical implications.

Numerous lateralized tasks have been identified as involving spatial processing, but the extent to which they use the same spatial process is largely unknown. The present research investigated relationships among significant asymmetries from seven visuo-spatial and two verbal tasks, combining samples from previous factor analytic experiments with those from three new studies (combined N=789). All of the spatial intercorrelations were negligible (r<0.20), unlike previous outcomes finding robust correlations within certain clusters of verbal asymmetries. However, lateral differences involving spatial quantitative processing on the one hand and figure-ground separation on the other, showed significant but independent correlations with one from visual lexical processing (word recognition). The results support three major conclusions. First, there are at least several and possibly many lateralized spatial processes. Second, hemispheric processes follow a modular architecture in preference to a diffuse or parallel distributed architecture. Finally, the dissociated correlations are consistent with a visual lexical processing model having both occipital and parietal components, potentially reconciling a current controversy over the cerebral localization of language.