Infants' attention to eyes is an independent, heritable trait predicting later verbal competence

From birth, infants orient preferentially to faces, and when looking at the face, they attend primarily to eyes and mouth — two areas that convey different types of information. Here, in a sample of 535 5-month-old infant twins, we assessed eye (relative to mouth) preference in early infancy. Eye preference was independent from all other concurrent traits measured, and had a moderate-to-high contribution from genetic influences (A = .57; 95% CI: .45, .66). Preference for eyes over mouth at 5 months predicted higher parent ratings of verbal competence in toddlerhood, but did not predict autistic traits. These results suggest that variation in eye looking reflects a type of biological niche picking emerging before infants can select their environments by other means (crawling or walking).

Quantitative multidimensional phenotypes improve genetic analysis of laterality traits

The heritability of handedness, the most commonly investigated lateralised phenotype, has been consistently estimated to be ~25%. Handedness is linked to brain asymmetries such as hemispheric dominance for language and it has been associated to psychiatric and neurodevelopmental disorders. Here, we investigated the genetics of handedness as well as foot and eye preference and their relationship with neurodevelopmental phenotypes. Parental left-side preference increased the chance of an individual to be left-sided for the same trait, with stronger maternal than paternal effects (n ≤ 4,042 family trios from the Avon Longitudinal Study of Parents and Children (ALSPAC)). By regressing out effects of sex, age, and the first two ancestry-informative principal components, we transformed categorical phenotypes (right, mixed, left) into quantitative measures for single nucleotide polymorphism (SNP) based heritability (SNP-h2). We found moderate SNP-h2 for transformed measures of hand (.21) and foot (.28) but negligible SNP-h2 for eye preference (.02) or the untransformed categorical measures (n ≤ 5,931). Genomic and behavioural structural equation modelling (SEM) in ALSPAC and a twin cohort from Hong Kong (n = 366) identified a shared genetic factor contributing to hand, foot, and eye preference, but no independent effects on individual phenotypes. Higher polygenic risk scores (PRS) for ADHD and genetic predisposition towards lower IQ and educational attainment (EA) were associated with left hand preference. This finding supports the idea of a right-handedness advantage on neurodevelopmental outcomes. This is the largest study conducted to date for multiple lateralised measures in the same individuals. Our analysis demonstrates how quantitative multidimensional laterality phenotypes are better suited to capture the underlying genetic component than simple left/right binary traits.

Motives and Laterality: Exploring the Links

Objectives We explored associations between the needs for power, achievement, and affiliation and functional cerebral asymmetries (FCAs), guided by three established hypotheses about the nature of these associations. Methods One-hundred-and-seven participants completed picture-story measures of dispositional motives and activity inhibition (AI), a frequent moderator of motive-behavior associations, tasks measuring FCAs (line bisection, chimeric emotional face judgments, turning bias, perceptual and response asymmetries on the Poffenberger task), self-reported laterality preferences (handedness, footedness, ear and eye preference), and interhemispheric interaction (crossed-uncrossed difference). They also completed an experiment manipulating hand contractions (left, right, both, neither) while they worked on a second picture-story motive measure. Results Dispositional power motivation was associated with stronger rightward asymmetry and less interhemispheric transfer in high-AI and stronger leftward asymmetry and more interhemispheric transfer in low-AI individuals. For the affiliation motive, findings were fewer and in the opposite direction of those for the power motive. These findings emerged for men, but not for women. Left- or right-hand contractions led to increases in power and achievement motivation, but not affiliation motivation. Only left-hand contractions led to decreased AI. Conclusions We discuss these findings in the context of sex-dimorphic organizing and activating effects of steroids on motives and laterality.

Lateralization of vigilance in geese: influence of flock size and distance to the source of disturbance

Left-eye preference, implicating right hemisphere advantage, is typical for vigilant behaviour of many vertebrates. Nevertheless, lateralization of vigilance may be manifested in other ways, such as different reactions to the danger viewed with the right and left eye. Here, we studied one-side biases in the orientation of white-fronted geese Anser albifrons feeding in flocks at different distances to the source of anthropogenic disturbance (a road with traffic) and in flocks of different sizes. The birds which used the left eye to monitor the road were at shorter distances to the road than the birds which used the right eye. The tendency to monitor the road with the right eye decreased with increasing flock size. Trade-offs between feeding, social and vigilant behaviour could explain these tendencies.

Laterality of Eye Use by Bottlenose (Tursiops truncatus) and Rough-Toothed (Steno bredanensis) Dolphins While Viewing Predictable and Unpredictable Stimuli

Laterality of eye use has been increasingly studied in cetaceans. Research supports that many cetacean species keep prey on the right side while feeding and preferentially view unfamiliar objects with the right eye. In contrast, the left eye has been used more by calves while in close proximity to their mothers. Despite some discrepancies across and within species, laterality of eye use generally indicates functional specialization of brain hemispheres in cetaceans. The present study aimed to examine laterality of eye use in bottlenose dolphins (Tursiops truncatus) and rough-toothed dolphins (Steno bredanensis) under managed care. Subjects were video-recorded through an underwater window while viewing two different stimuli, one predictable and static and the other unpredictable and moving. Bottlenose dolphins displayed an overall right-eye preference, especially while viewing the unpredictable, moving stimulus. Rough-toothed dolphins did not display eye preference while viewing stimuli. No significant correlations between degree of laterality and behavioral interest in the stimuli were found. Only for bottlenose dolphins were the degree of laterality and curiosity ratings correlated. This study extends research on cetacean lateralization to a species not extensively examined and to stimuli that varied in movement and degree of predictability. Further research is needed to make conclusions regarding lateralization in cetaceans.

Eye Preference for Emotional Stimuli in Sichuan Snub-Nosed Monkeys

This study presents the first evidence of effects of applying both positive and negative stimuli simultaneously on visual laterality in Old World monkeys. Thirteen captive individuals of Sichuan snub-nosed monkeys (<i>Rhinopithecus roxellana</i>) were chosen as focal subjects in the monocular box task. In total, 4 emotional categories (the preferred, the novel, the neutral, and the fearful) of visual stimuli were applied, and eye preference was recorded when individuals looked at each stimulus through an observation hole in the box. We found evidence of visual laterality at the individual level, but not at the group level for each stimulus. For the preferred stimulus, 9 individuals showed significant right-eye preference while 4 individuals showed significant left-eye preference. For the other 3 stimuli, 7 individuals displayed significant right-eye preference while 6 individuals displayed significant left-eye preference. Totally, 11 of 13 individuals showed consistency in the visual laterality direction (7 right-eye preference and 4 left-eye preference) across the 4 stimuli. The remaining 2 individuals displayed right-eye preference for the preferred stimulus while they showed left-eye preference for the other 3 stimuli. There was no significant difference among various stimuli regarding the direction of visual laterality. However, there was a significant difference in the strength of visual laterality among various stimulus categories. The strength of visual laterality for the preferred stimulus was significantly lower than that for the other 3 stimuli. The strength of visual laterality for the fearful stimulus was significantly higher than that for the novel stimulus and the neutral stimulus. Furthermore, the looking duration for the preferred stimulus was significantly higher than that for the other 3 stimuli. The looking duration for the novel stimulus was significantly higher than that for the neutral stimulus and the fearful stimulus. The looking duration for the neutral stimulus was significantly higher than that for the fearful stimulus. Our findings indicate emotional valence of stimuli significantly influence eye looking duration and the strength of visual laterality but not for the direction of visual laterality in this species. Taken together, emotional valence of stimuli plays an important role in the eye use of <i>R. roxellana</i>.

Lateral Asymmetry of Brain and Behaviour in the Zebra Finch, Taeniopygia guttata

Lateralisation of eye use indicates differential specialisation of the brain hemispheres. We tested eye use by zebra finches to view a model predator, a monitor lizard, and compared this to eye use to view a non-threatening visual stimulus, a jar. We used a modified method of scoring eye preference of zebra finches, since they often alternate fixation of a stimulus with the lateral, monocular visual field of one eye and then the other, known as biocular alternating fixation. We found a significant and consistent preference to view the lizard using the left lateral visual field, and no significant eye preference to view the jar. This finding is consistent with specialisation of the left eye system, and right hemisphere, to attend and respond to predators, as found in two other avian species and also in non-avian vertebrates. Our results were considered together with hemispheric differences in the zebra finch for processing, producing, and learning song, and with evidence of right-eye preference in visual searching and courtship behaviour. We conclude that the zebra finch brain has the same general pattern of asymmetry for visual processing as found in other vertebrates and suggest that, contrary to earlier indications from research on lateralisation of song, this may also be the case for auditory processing.

Spatial scale and distribution of neurovascular signals underlying decoding of orientation and eye of origin from fMRI data

Multivariate pattern analysis of functional magnetic resonance imaging (fMRI) data is widely used, yet the spatial scales and origin of neurovascular signals underlying such analyses remain unclear. We compared decoding performance for stimulus orientation and eye of origin from fMRI measurements in human visual cortex with predictions based on the columnar organization of each feature and estimated the spatial scales of patterns driving decoding. Both orientation and eye of origin could be decoded significantly above chance in early visual areas (V1–V3). Contrary to predictions based on a columnar origin of response biases, decoding performance for eye of origin in V2 and V3 was not significantly lower than that in V1, nor did decoding performance for orientation and eye of origin differ significantly. Instead, response biases for both features showed large-scale organization, evident as a radial bias for orientation, and a nasotemporal bias for eye preference. To determine whether these patterns could drive classification, we quantified the effect on classification performance of binning voxels according to visual field position. Consistent with large-scale biases driving classification, binning by polar angle yielded significantly better decoding performance for orientation than random binning in V1–V3. Similarly, binning by hemifield significantly improved decoding performance for eye of origin. Patterns of orientation and eye preference bias in V2 and V3 showed a substantial degree of spatial correlation with the corresponding patterns in V1, suggesting that response biases in these areas originate in V1. Together, these findings indicate that multivariate classification results need not reflect the underlying columnar organization of neuronal response selectivities in early visual areas. NEW & NOTEWORTHY Large-scale response biases can account for decoding of orientation and eye of origin in human early visual areas V1–V3. For eye of origin this pattern is a nasotemporal bias; for orientation it is a radial bias. Differences in decoding performance across areas and stimulus features are not well predicted by differences in columnar-scale organization of each feature. Large-scale biases in extrastriate areas are spatially correlated with those in V1, suggesting biases originate in primary visual cortex.

Do Belugas (Delphinapterus leucas), Bottlenose Dolphins (Tursiops truncatus), & Pacific White-Sided Dolphins (Lagenorhynchus obliquidens) Display Lateralized Eye Preference when Presented with Familiar or Novel Objects?

Lateralization of behaviors and information processing are common across species. Hypothesized to be crucial for more efficient responding to environmental stimuli, lateralization has been investigated for a number of topics. Cetaceans are proposed to be hemispheric specialists, given a small corpus callosum, complete decussation of the optic nerve, and the ability to respond to a different visual stimulus presented to each eye simultaneously. Research with cetaceans has shown strong biases in a number of behaviors, including swimming, foraging, social interactions, and responses to myriad visual stimuli. Given similar evolutionary pressures, different species of cetaceans should display similar lateralized preferences. Previous research with bottlenose dolphins in managed care and wild striped dolphins indicated a right eye preference when viewing unfamiliar objects. The purpose of the current study was to evaluate the eye preference of belugas, bottlenose dolphins, and Pacific white-sided dolphins (lags) in managed care when viewing familiar and unfamiliar objects. The results from 11 belugas, 5 bottlenose dolphins, and 5 lags indicated that consistent group level eye preferences were not present. The belugas preferred to view both types of objects with both eyes, with the majority of the belugas showing a left-eye preference when a monocular gaze was used. Bottlenose dolphins tended to view both objects with their right eye while lags used their left eye when viewing objects. These results may have been affected by viewing objects below water versus above water. The belugas and the Pacific white-sided dolphins were able to view the objects below water, which may have elicited more naturalistic visual examinations of the objects (i.e., greater ecological validity). Viewing objects within one’s habitat may facilitate the discrimination of an object rather than simply its detection, which is may be more likely when encountering stimuli above the surface of the water as the bottlenose dolphins had to do in the present and past research. Future research should compare if presentation of the stimulus above water versus below water affects the eye preference displayed.