ABSTRACT Reliable measures of language laterality are essential for understanding relationships between speech and other lateralized functions. In a previous study (Grant et al., 2023. Testing the relationship between lateralization on sequence-based motor tasks and language laterality using an online battery. Laterality, 28(1), 1–31), an online verbal visual half-field (vVHF) task assessed speech production laterality but showed limited reliability and validity. The present study conducted novel analyses linking this measure with functional transcranial Doppler ultrasound (fTCD) data collected from the same sample as part of a separate project (Parker et al., 2022. Inconsistent language lateralisation: Testing the dissociable language laterality hypothesis using behaviour and lateralised cerebral blood flow. Cortex, 154, 105–134). In total, 187 participants completed both the online battery and an in-person fTCD sentence-generation task. Results confirmed robust left lateralization for speech production across handedness groups. However, laterality indices from the vVHF task did not correlate with the fTCD measure, reinforcing concerns about the validity of the online paradigm. Replicating previous findings, no significant association was observed between categorical measures of speech and motor laterality. Exploratory analyses revealed a significant positive correlation between motor laterality indices and fTCD speech laterality.

ABSTRACT Pseudoneglect refers to the tendency for neurologically normal individuals to overattend to the left side of near space, which shifts to the right in far space. Such attentional asymmetries affect daily activities, such as navigation, where individuals have been found to deviate to the right when passing through an aperture. Interestingly, a representational form of pseudoneglect exists for briefly presented stimuli that need to be held in memory, whereby attention is shifted to the left. The current study examined whether representational pseudoneglect exists in a simulated navigation environment. Participants navigated through the centre of a computer-generated doorway or line. On perceptual trials, the doorway/line would remain on screen, while for representational trials, the doorway/line would disappear from the screen. Significant rightward biases were found for both the perceptual and representational trials of the line and doorway conditions, with the biases being exacerbated on representational trials. Results indicate that the significant load involved with holding a representation of the stimulus in memory may best explain the exacerbation of rightward shifts of attention in the present study.

ABSTRACT Readers must be able to make inferences to maintain coherence during reading. Prior research suggests that the cerebral hemispheres process inferences differently depending on level of textual constraint, however, it is not clear when these hemispheric differences occur during reading. The current study investigates how levels of textual constraint influences the hemispheric processing of bridging inferences. Participants read texts promoting a strongly constrained (Experiment 1) or weakly-constrained (Experiment 2) bridging inference and then performed a lexical decision for targets presented to either the left or right hemisphere. Using event-related potential (ERP) analysis, N400 and P600 waveforms were examined during the target presentation. For strongly constrained inferences, a larger N400 effect was found in the right hemisphere than the left hemisphere. For weakly constrained inferences, there was a larger N400 effect overall, but no differences between the hemispheres. In addition, no hemispheric differences were observed for the P600 waveform between the strongly and weakly constrained inferences. Thus, hemispheric asymmetries seem to occur during the early stages of text processing when readers might generate both strongly and weakly-constrained inferences.

ABSTRACT Personality traits are linked to a variety of cognitive and socio-emotional factors, including lateralization patterns. Autism, prosopagnosia, and atypical cradling have been associated with altered lateralization and socio-emotional processing. This study explores how autism traits, cradling-side preferences, and face recognition abilities relate to individual personality differences. Three-hundred neurotypical adults (150 males) completed an online survey including the imaged cradling preference and three validated questionnaires: the Autism spectrum Quotient (AQ), Prosopagnosia Index-20 (PI-20), and the Big Five Personality Questionnaire (BFQ). Results showed a strong left-cradling bias (LCB) unaffected by sex, handedness, parental status, autism traits, or face recognition abilities. AQ negatively predicted Extraversion, Agreeableness, Emotional Stability, and Openness. LCB correlated with higher Agreeableness and moderated the negative association between AQ and Extraversion. These findings suggest a potential link between cradling preferences, autism traits, and personality, possibly reflecting reduced right-hemisphere specialization in emotional processing and social behaviour.

ABSTRACT An analysis of the handedness of the four members of the British rock band The Beatles is presented. Implications for the roles of the left and right hands in the playing of different musical instruments, for the roles of the left versus right hemispheres in song writing, and for the Beatle’s legacy in popular culture are discussed.

ABSTRACT Facial emotion processing (FEP) tends to be right hemisphere lateralized. This right-hemispheric bias (RHB) for FEP varies within and between individuals. The aim of the present research was to examine evidence pertaining to the prominent theories of FEP hemispheric bias as measured by a half-emotional half-neutral (no emotion) chimeric faces task. FEP hemispheric bias was indexed using laterality quotients (LQs) calculated from a Chimeric Faces Task completed by 427 adults recruited from the general population aged 18–67 years. Participants indicated which of two identical (but mirrored) emotional-neutral chimeric faces were more emotive. While all investigated emotions (fear, anger, and happiness) were right lateralized, fear was significantly more right lateralized than anger and happiness. These results provide evidence for both the right hemisphere hypothesis and the motivational hypothesis of emotion perception.

ABSTRACT For most individuals, language is predominately localized to the left hemisphere of the brain and visuospatial processing to the right. This is the typical pattern of functional lateralization. Evolutionary theories of lateralization suggest that the typical pattern is most common as it delivers a cognitive advantage. In contrast, deviations from the typical pattern may lead to poorer cognitive abilities. The aim of this systematic review was to assess the evidence for an association between patterns of language and visuospatial lateralization and measures of cognitive ability. We screened 9,122 studies, retrieved from PsycINFO, EMBASE, MEDLINE, PubMed, and Web of Science. The 17 studies that met our selection criteria revealed little evidence for an advantage of typical compared to atypical patterns of lateralization, although atypical lateralization patterns were related to worse language comprehension, spatial ability, and reading, but further research is needed to confirm this. We conclude with recommendations that future researchers recruit larger samples of atypical participants, and consider strength of lateraliation and bilaterality when analysing functional lateralization patterns.

ABSTRACT Several factors affect the development of lateralization such as hormones and light exposure during early development. Laterality also often correlates with other behavioral traits. To examine whether there is a common mechanism underlying the development of laterality and other behaviors, we manipulated laterality by exposing embryos of the Western rainbowfish (Melatotaenia australis) to light or continuous darkness during early development and determined whether a shift in laterality was associated with a change in behavior in a novel environment test at two different ages. We found that exposing eggs to darkness led to offspring that displayed significantly less lateralized behavior in the mirror test two weeks after hatching than offspring from eggs exposed to light. Interestingly, the effects of rearing condition were lost by 3 months of age. These data suggest that exposure to light can influence laterality very early in development, but such bias can be overwritten by developmental processes post-hatch. Moreover, our manipulation of laterality apparently had no influence on exploration suggesting independent causal mechanisms. The experimental manipulation of light exposure during development could be a useful tool for enhancing individuals with a specific laterality and behavioral traits to aid future research into the causes and consequences of laterality.

ABSTRACT Studies have highlighted an association between motor laterality and speech production laterality. It is thought that common demands for sequential processing may underlie this association. However, most studies in this area have relied on relatively small samples and have infrequently explored the reliability of the tools used to assess lateralization. We, therefore, established the validity and reliability of an online battery measuring sequence-based motor laterality and language laterality before exploring the associations between laterality indices on language and motor tasks. The online battery was completed by 621 participants, 52 of whom returned to complete the battery a second time. The three motor tasks included in the battery showed good between-session reliability (r ≥ .78) and were lateralized in concordance with hand preference. The novel measure of speech production laterality was left lateralized at population level as predicted, but reliability was less satisfactory (r = .62). We found no evidence of an association between sequence-based motor laterality and language laterality. Those with a left-hand preference were more strongly lateralized on motor tasks requiring midline crossing; this effect was not observed in right-handers. We conclude that there is little evidence of the co-lateralization of language and sequence-based motor skill on this battery.