The present investigation evaluates the effects of multiple language acquisition history on brain functional organization for language. To address a range of findings concerning the functional cerebral lateralization of the native (L1) and second languages (L2) of bilinguals, a meta-analysis was conducted on 71 studies that used behavioral paradigms to assess bilingual laterality. The predictive value of a number of theoretically identified moderators of cerebral asymmetry for language was assessed, namely, the age of second language (L2) acquisition, fluency in theL2, participant sex, experimental paradigm, linguistic task demands, relatedness of L1 and L2 structures, and context of language use. The results revealed no differences in the laterality of first and second languages within L2 acquisition age groups. Of the moderators tested, age of L2 acquisition was identified as the most reliable predictor of the direction of laterality. The conditions under which systematic similarities and differences in language lateralization among bilingual subgroups emerge are discussed in terms of implications for current models and theories concerning the functional organization of language in the bilingual brain.

There is a clearly established division of functional processing between left and right hemispheres of the brain, with the pattern showing robust consistency across individuals. The finding of functional differences between the hemispheres of the brain raises two important questions: First, what mechanisms gave rise to the lateralized biases in processing function? Second, what are the consequences of functional asymmetry of cognitive processing in the human brain on our everyday behaviour? Examining the mechanisms that give rise to cerebral lateralization, Experiments 1 and 2 tested the assumption that there is a causal relationship in the degree and direction of lateralization between left- and right-hemisphere dominant tasks. In experiment 1, this relationship between left-hemisphere processing of speech sounds and right-hemisphere processing of emotional vocalizations was examined using dichotic listening tasks. An overall complementary pattern of lateralization was observed across participants, but no significant relationship was found for degree of lateralization of speech and emotional vocalization processing within individuals. These results support the view that functions in the left and right hemispheres are independently lateralized. In Experiment 2 we examined the relationship pattern in degree of lateralization between linguistic processing and melody recognition using dichotic-listening tasks. The expected left-hemisphere advantage was observed for the linguistic processing task, but the expected right-hemisphere advantage was not observed for the melody recognition task, precluding an informative assessment of complementarity between the two tasks. The division of processing between the two hemispheres of the brain has been shown to result in lateralized performance advantages and behavioural biases. Examining these consequences of lateralization, Experiments 3 through 6 explored the influence of lateral biases on everyday behaviour. Experiments 3 and 4 examined the influence of asymmetries in facial attractiveness on posing biases. Despite evidence suggesting that the right side of the face is found to be more attractive, professional modeling photographs examined in Experiment 3 revealed a leftward posing bias suggesting that asymmetries in facial attractiveness are not dominant in influencing posing behaviour, even when the purpose of the image is to highlight attractiveness. Experiment 4 controlled for image selection biases by examining posing behaviour directly and revealed a rightward posing bias when participants were asked to emphasize their attractiveness. Experiments 5 and 6 examined the influence of lateralized cognitive processing demands on seating preferences. Experiment 5 investigated the real-world seating patterns of theatre patrons during actual film screenings. It was found that, when processing expectations relied on right-hemisphere dominant processes, such as emotional, facial, or visuospatial processing, people were more likely to choose a seat to the right side of the room. Experiment 6 was designed to test two competing theories that have attempted to explain seating biases: one posits that expectation of processing demand drives the bias; the other posits that basic motor asymmetries drive the bias. Through naturalistic observation, I recorded classroom-seating choices of university students using photographs. When processing expectations relied on left-hemisphere dominant processes, such as linguistic processing, people were more likely to choose seats on the left side of the classroom; this finding contrasts the right side bias observed in theatre seating studies, providing evidence that expectation of processing demands influences the seating bias. Addressing the mechanisms that guide the evolution of lateralization, no support for the assumption of a causal relationship between complementary left-and right-lateralized cognitive functions was found. Additionally, examination of asymmetries in everyday behaviours such as seating and posing provide evidence that the lateralization of cognitive functions has a direct influence on human behaviour and interaction with the environment.

The present investigation evaluates the effects of multiple language acquisition history on brain functional organization for language. To address a range of findings concerning the functional cerebral lateralization of the native (L1) and second languages (L2) of bilinguals, a meta-analysis was conducted on 71 studies that used behavioral paradigms to assess bilingual laterality. The predictive value of a number of theoretically identified moderators of cerebral asymmetry for language was assessed, namely, the age of second language (L2) acquisition, fluency in theL2, participant sex, experimental paradigm, linguistic task demands, relatedness of L1 and L2 structures, and context of language use. The results revealed no differences in the laterality of first and second languages within L2 acquisition age groups. Of the moderators tested, age of L2 acquisition was identified as the most reliable predictor of the direction of laterality. The conditions under which systematic similarities and differences in language lateralization among bilingual subgroups emerge are discussed in terms of implications for current models and theories concerning the functional organization of language in the bilingual brain.

The purpose of this study was to investigate the relationship between mixed eye-hand dominance and letter/word reversals in learning disabled and normal readers. Previous research had shown links between mixed dominance and reading disabilities, especially those disabilities related to visuo-spatial deficits. However, due to the different approaches to conceptualizing lateral preferences, the wide variety of methods used to assess laterality, and the heterogeneity of subjects exhibiting reading disabilities, many studies have been contradictory and inconclusive. This study was designed to: assess laterality on a continuum, investigate the specific area of mixed eye-hand dominance, and determine if there is a statistically significant relationship between the degree of mixed dominance and the specific reading problem of letter and word reversals.The research sample consisted of 53 learning disabled males and 44 males from regular education classrooms, randomly selected from a public school system in northern Indiana. Mixed eye-hand dominance was assessed by the General Laterality Factor and the Visual Activities Factor of the Lateral Preference Schedule. The degree of letter/word reversal difficulty was-determined by the Jordan Left-Right Reversal Test. Each subject was administered both instruments either individually or in small groups.The data was analyzed for statistical significance by computing Pearson product moment correlation coefficients. To compare the learning disabled readers and normal readers for significant differences in age and the degree of mixed eye-hand dominance, t tests were conducted. Two research questions were then addressed by examining the findings:Research Question #1: Is there a statistically significant relationship between mixed eye-hand dominance and letter/word reversal errors in learning disabled and normal readers? A statistically significant difference was found between the degree of mixed eye-hand dominance and reversal errors in the learning disabled group. No other statistically significant relationships were found.Research Question #2: Is there a greater degree of mixed eye-hand dominance in learning disabled students than in normal readers? There were no statistically significant differences between learning disabled and normal readers in the degree of mixed eye-hand dominance.It was concluded that there were no statistically significant relationships between mixed eye-hand dominance and reversal errors in normal readers or when groups of normal readers and learning disabled students were combined. There was, however, a statistically significant positive relationship between mixed dominance and reversal errors when learning disabled students were grouped separately. The greater the degree of mixed eye-hand dominance, the higher the reversal error score in learning disabled students.Attempts to develop more sensitive and reliable instruments to assess lateral preferences and specific reading problems were recommended. Additionally, studies investigating the relationship between lateral preferences and reading performance should continue. / Department of Educational Psychology

Five tachistoscopic studies were conducted to investigate patterns of hemispheric specialization for different types of word pair comparisons among monolinguals and fluent bilingual adults. Bilinguals were further grouped as "early" or "late" depending on whether their second language was acquired in infancy or in adolescence. All groups were faster at making orthographic comparisons for left visual field input but were faster in the right visual field for phonological and syntactic judgments. Semantic comparisons yielded no visual field asymmetries for monolinguals or late bilinguals but yielded a left visual field superiority for early bilinguals. Group differences in response strategy were also noted whereby early bilinguals favoured semantic processing and late bilinguals surface processing. The results are interpreted to suggest that lateralization patterns are primarily influenced by task-related processing demands but that early versus late onset of bilingualism predisposes the use of different processing strategies for performing a particular task.

Musicians comprise a unique population whereby persistent musical practice involving complex cognitive and motor tasks dates back to childhood when the potential for neural plasticity is at its highest. Accordingly, it has been speculated that musical training results in neural structural and functional differences between musicians and non-musicians. In particular, there is evidence to indicate parietal regions are more equally lateralized in musicians, but research investigating visuospatial abilities and lateralization in musicians is scarce. Studies 1 and 2 aimed to assess the visuospatial ability and cognitive processing speed of adult musicians versus ‪demographically and educationally matched non-musicians. ‪Musicians performed more quickly and more accurately than non-musicians in two tasks of visuospatial ability, and completed more items than non-musicians in three tasks of processing speed, suggesting ‪musicians had better ‪visuospatial ability and a faster speed of processing. Studies 3 and 4 aimed to investigate ‪visuospatial attention in ‪these groups using a line-bisection task and a visual discrimination task. On both tasks musicians demonstrated more balanced visuospatial attention with a slight bias to the right hemispace, which was in contrast to the non-musicians’ bias to the left hemispace, a natural phenomenon known as ‘right pseudoneglect’. In Study 5, the laterality of visual processing in musicians and non-musicians was further investigated by comparing electrophysiological interhemispheric transfer time (IHTT) of lateralized visual stimuli across the corpus callosum. Non-musicians had faster right-to-left than left-to-right IHTT consistent with previous research, whilst musicians had more balanced IHTT in both directions and faster left-to-right transfer than non-musicians. Absolute latency patterns revealed similar results and consistently demonstrated more balanced visual processing in musicians. The behavioural data, analysed in Study 6, revealed a tendency (n.s.) for the ‪musician group to respond more quickly to stimuli presented in the right visual field than to stimuli presented in the left visual field, whilst ‪non-musicians did not show this pattern. Overall, the results indicate that musicians have enhanced visuospatial ability and are less lateralized for visuospatial attention and perception than non-musicians. The results are discussed in relation to plastic developmental changes that may be caused by extended musical training from childhood. Specifically, it is proposed that musical training in early life may elicit a process of myelination that is more bilaterally distributed than myelination in non-musicians.

Musicians comprise a unique population whereby persistent musical practice involving complex cognitive and motor tasks dates back to childhood when the potential for neural plasticity is at its highest. Accordingly, it has been speculated that musical training results in neural structural and functional differences between musicians and non-musicians. In particular, there is evidence to indicate parietal regions are more equally lateralized in musicians, but research investigating visuospatial abilities and lateralization in musicians is scarce. Studies 1 and 2 aimed to assess the visuospatial ability and cognitive processing speed of adult musicians versus ‪demographically and educationally matched non-musicians. ‪Musicians performed more quickly and more accurately than non-musicians in two tasks of visuospatial ability, and completed more items than non-musicians in three tasks of processing speed, suggesting ‪musicians had better ‪visuospatial ability and a faster speed of processing. Studies 3 and 4 aimed to investigate ‪visuospatial attention in ‪these groups using a line-bisection task and a visual discrimination task. On both tasks musicians demonstrated more balanced visuospatial attention with a slight bias to the right hemispace, which was in contrast to the non-musicians’ bias to the left hemispace, a natural phenomenon known as ‘right pseudoneglect’. In Study 5, the laterality of visual processing in musicians and non-musicians was further investigated by comparing electrophysiological interhemispheric transfer time (IHTT) of lateralized visual stimuli across the corpus callosum. Non-musicians had faster right-to-left than left-to-right IHTT consistent with previous research, whilst musicians had more balanced IHTT in both directions and faster left-to-right transfer than non-musicians. Absolute latency patterns revealed similar results and consistently demonstrated more balanced visual processing in musicians. The behavioural data, analysed in Study 6, revealed a tendency (n.s.) for the ‪musician group to respond more quickly to stimuli presented in the right visual field than to stimuli presented in the left visual field, whilst ‪non-musicians did not show this pattern. Overall, the results indicate that musicians have enhanced visuospatial ability and are less lateralized for visuospatial attention and perception than non-musicians. The results are discussed in relation to plastic developmental changes that may be caused by extended musical training from childhood. Specifically, it is proposed that musical training in early life may elicit a process of myelination that is more bilaterally distributed than myelination in non-musicians.

Musicians comprise a unique population whereby persistent musical practice involving complex cognitive and motor tasks dates back to childhood when the potential for neural plasticity is at its highest. Accordingly, it has been speculated that musical training results in neural structural and functional differences between musicians and non-musicians. In particular, there is evidence to indicate parietal regions are more equally lateralized in musicians, but research investigating visuospatial abilities and lateralization in musicians is scarce. Studies 1 and 2 aimed to assess the visuospatial ability and cognitive processing speed of adult musicians versus ‪demographically and educationally matched non-musicians. ‪Musicians performed more quickly and more accurately than non-musicians in two tasks of visuospatial ability, and completed more items than non-musicians in three tasks of processing speed, suggesting ‪musicians had better ‪visuospatial ability and a faster speed of processing. Studies 3 and 4 aimed to investigate ‪visuospatial attention in ‪these groups using a line-bisection task and a visual discrimination task. On both tasks musicians demonstrated more balanced visuospatial attention with a slight bias to the right hemispace, which was in contrast to the non-musicians’ bias to the left hemispace, a natural phenomenon known as ‘right pseudoneglect’. In Study 5, the laterality of visual processing in musicians and non-musicians was further investigated by comparing electrophysiological interhemispheric transfer time (IHTT) of lateralized visual stimuli across the corpus callosum. Non-musicians had faster right-to-left than left-to-right IHTT consistent with previous research, whilst musicians had more balanced IHTT in both directions and faster left-to-right transfer than non-musicians. Absolute latency patterns revealed similar results and consistently demonstrated more balanced visual processing in musicians. The behavioural data, analysed in Study 6, revealed a tendency (n.s.) for the ‪musician group to respond more quickly to stimuli presented in the right visual field than to stimuli presented in the left visual field, whilst ‪non-musicians did not show this pattern. Overall, the results indicate that musicians have enhanced visuospatial ability and are less lateralized for visuospatial attention and perception than non-musicians. The results are discussed in relation to plastic developmental changes that may be caused by extended musical training from childhood. Specifically, it is proposed that musical training in early life may elicit a process of myelination that is more bilaterally distributed than myelination in non-musicians.

Past research investigating stuttering has cited atypical cerebral lateralization in adults who stutter (AWS) during speech production. The purpose of this study was to measure cerebral activation in AWS as indicated by lip asymmetry. The study included five AWS (mean age = 26 years of age) and five adults who do not stutter (AWNS) (mean age = 25 years of age). The tasks included single-word productions, single-sentence readings and lip pursings. The peak electromyographic (EMG) amplitude was determined for the left upper, right upper, left lower and right lower lip quadrants around the mouth. Overall, EMG amplitudes were higher for the lower lip than the upper lip. Based on examination of peak EMG amplitude, significant differences were found between speaker groups. For both speech and non-speech tasks, the highest EMG amplitude for the AWS and AWNS groups were on the left lower and right lower sides of the mouth, respectively. The AWNS group showed strong correlations in EMG activity across the four lip sites (r>0.97), indicating an overall synchronous lip activity during speech and non-speech tasks. In contrast, the AWS group showed a strong correlation (r=0.97) only for the left upper and left lower lips while the other lip pairings were not strongly correlated (r<0.738) indicating otherwise reduced synchronous lip activity. While the small sample size suggests caution, clear differences in the pattern of lip EMG activity demonstrated in the present study provides evidence of differences between AWS and AWNS in the cerebral activation governing lip movement. The greater left lip activity observed in AWS was indicative of greater right hemisphere cerebral activation while increased right lip activity was indicative of greater left hemisphere participation in AWNS. The results of the present study provided support for the hypotheses of reversed lateralization for speech and non-speech processing and reduced coordination of speech musculature in AWS.

Musicians comprise a unique population whereby persistent musical practice involving complex cognitive and motor tasks dates back to childhood when the potential for neural plasticity is at its highest. Accordingly, it has been speculated that musical training results in neural structural and functional differences between musicians and non-musicians. In particular, there is evidence to indicate parietal regions are more equally lateralized in musicians, but research investigating visuospatial abilities and lateralization in musicians is scarce. Studies 1 and 2 aimed to assess the visuospatial ability and cognitive processing speed of adult musicians versus ‪demographically and educationally matched non-musicians. ‪Musicians performed more quickly and more accurately than non-musicians in two tasks of visuospatial ability, and completed more items than non-musicians in three tasks of processing speed, suggesting ‪musicians had better ‪visuospatial ability and a faster speed of processing. Studies 3 and 4 aimed to investigate ‪visuospatial attention in ‪these groups using a line-bisection task and a visual discrimination task. On both tasks musicians demonstrated more balanced visuospatial attention with a slight bias to the right hemispace, which was in contrast to the non-musicians’ bias to the left hemispace, a natural phenomenon known as ‘right pseudoneglect’. In Study 5, the laterality of visual processing in musicians and non-musicians was further investigated by comparing electrophysiological interhemispheric transfer time (IHTT) of lateralized visual stimuli across the corpus callosum. Non-musicians had faster right-to-left than left-to-right IHTT consistent with previous research, whilst musicians had more balanced IHTT in both directions and faster left-to-right transfer than non-musicians. Absolute latency patterns revealed similar results and consistently demonstrated more balanced visual processing in musicians. The behavioural data, analysed in Study 6, revealed a tendency (n.s.) for the ‪musician group to respond more quickly to stimuli presented in the right visual field than to stimuli presented in the left visual field, whilst ‪non-musicians did not show this pattern. Overall, the results indicate that musicians have enhanced visuospatial ability and are less lateralized for visuospatial attention and perception than non-musicians. The results are discussed in relation to plastic developmental changes that may be caused by extended musical training from childhood. Specifically, it is proposed that musical training in early life may elicit a process of myelination that is more bilaterally distributed than myelination in non-musicians.