Examining the sex difference in lateralisation for processing facial emotion: Does biological sex or psychological gender identity matter?

Functional lateralization in social-emotional processing: The influence of sexual orientation and gender identity on cradling preferences

The left-cradling bias (i.e., the motor asymmetry for cradling infants on the left side) has often been associated to the right-hemispheric social-emotional specialization, and it has often been reported to be stronger in females than in males. In this study we explored the effects of sexual orientation and gender identity on this lateral bias by means of a web-based investigation in a sample of adults (485 biological females and 196 biological males) recruited through LGBTQIA+ networks and general university forums. We exploited a cradling imagery task to assess participants' cradling-side preference, and standardized questionnaires to assess participants' homosexuality (Klein Sexual Orientation Grid) and gender nonconformity (Gender Identity/Gender Dysphoria Questionnaire for Adults and Adolescents). Results confirmed the expected left-cradling bias across all sexual orientation groups except for heterosexual males. Importantly, higher homosexuality scores were associated with higher proportions of left cradling in males. These results suggest that sexual orientation can influence cradling preference in males, indicating a complex interaction between biological and psychological factors in the laterality of social-emotional processing. Finally, the left-cradling bias seems to confirm its role as a behavioral proxy of social-emotional functional lateralization in humans.

Comparing two versions of the Chimeric Face Test: A pilot investigation

The Chimeric Face Test (CFT) is a widely used behavioral measure of degree of lateralization for emotion processing. The Pictures of Facial Affect (Ekman, 1976 [Pictures of facial affect. Consulting Psychologists Press.]) have often been used to create chimeras for this task but have widely been critiqued due to lack of ethnic diversity and small stimuli numbers. In this brief study participants (N = 45) completed two Chimeric Face Tests, one using the Pictures of Facial Affect and one using the NimStim facial stimuli (Tottenham et al., 2009 [The NimStim set of facial expressions: Judgments from untrained research participants. Psychiatry Research, 168(3), 242-249]). The laterality scores were compared across measures. The results show the two measures are related; laterality quotients showed a strong correlation between the two tasks. Participants showed a left-visual field bias on both tasks, indicative of a right-hemisphere bias for the processing of emotions. The NimStim Chimeric Face Test however was found to give a more conservative estimate of degree of lateralization. The NimStim Chimeric Face Test is discussed as a valid measure for examining lateralization for emotion processing, The extent to which different versions of the Chimeric Face Test are comparable is discussed.

Sex/Gender Differences in Brain Lateralisation and Connectivity

There is now a significant body of literature concerning sex/gender differences in the human brain. This chapter will critically review and synthesise key findings from several studies that have investigated sex/gender differences in structural and functional lateralisation and connectivity. We argue that while small, relative sex/gender differences reliably exist in lateralisation and connectivity, there is considerable overlap between the sexes. Some inconsistencies exist, however, and this is likely due to considerable variability in the methodologies, tasks, measures, and sample compositions between studies. Moreover, research to date is limited in its consideration of sex/gender-related factors, such as sex hormones and gender roles, that can explain inter-and inter-individual differences in brain and behaviour better than sex/gender alone. We conclude that conceptualising the brain as 'sexually dimorphic' is incorrect, and the terms 'male brain' and 'female brain' should be avoided in the neuroscientific literature. However, this does not necessarily mean that sex/gender differences in the brain are trivial. Future research involving sex/gender should adopt a biopsychosocial approach whenever possible, to ensure that non-binary psychological, biological, and environmental/social factors related to sex/gender, and their interactions, are routinely accounted for.

Laterality and visuospatial strategies among young children: A novel 3D-2D transcription task

Recent findings showed that children, like adults, exhibit directional biases leading to asymmetrical drawings. This appears to be the result of a complex interaction between several biological, motoric, and cultural factors. We created a drawing task designed to investigate the influence of laterality (i.e., hemispherical functional specialization and handedness) and sex on children's graphical asymmetries. This task consists of transcribing a symmetrical three-dimensional landscape model to a two-dimensional representation. Sixty-six French pre-school children, aged between 5 and 6 years, were asked to undertake the 3D-2D transcription task, as well as the classical Alter's directionality task. The novel task exhibited higher sensitivity than the Alter's directionality test when examining the spatial biases resulting from handedness, and sex. Specific drawing patterns related to these variables were identified. These results suggest that, in addition to the influence of biomechanical factors and handedness, sex plays a role in children's early graphomotor development. They also support the influence of laterality as a key factor underlying early directional biases.

Gender Role, But Not Sex, Shapes Humans' Susceptibility to Emotion

It is unknown whether the famous sex-related difference in emotion processing is accounted for by biological sex, gender role, or their interaction. To clarify the issue, in Study 1 we recorded event-related potentials in response to negative and positive images of diverse intensities when 47 masculine (26 males) and 47 feminine (22 males) subjects performed a non-emotional task. The occipital P1 and N1 amplitudes were larger in women than in men, while feminine subjects showed larger N1 amplitudes than masculine subjects, regardless of sex. Moreover, feminine subjects showed enhanced frontocentral N2 (210-270 ms) amplitudes for highly and mildly negative than for neutral stimuli, while masculine subjects showed an emotion effect only for highly negative stimuli. The feminine-specific effect for mildly negative stimuli was positively correlated to the feminine score, and this correlation was located to the anterior cingulate and the superior and medial frontal gyri. Furthermore, feminine but not masculine subjects showed enhanced parietal P3 (330-560 ms) amplitudes for highly and mildly positive than for neutral stimuli, an effect positively related to the feminine score and localized to the precuneus, posterior cingulate, and superior temporal gyrus. Machine learning analyses verified that single-trial N2 and P3 amplitudes of feminine subjects reliably discriminated the intensity of negative and positive stimuli, respectively. For ecological considerations, in Study 2 we used an observational approach (n = 300) and confirmed that feminine gender role, rather than biological sex, predicted individual differences in daily experience of emotion-related psychopathological symptoms. These findings provide solid evidence for the critical impact of gender role rather than sex on emotional susceptibility.

Insular Risk Processing Predicts Alcohol Use Via Externalizing Pathway in Male Adolescents

OBJECTIVE

Male adolescents exhibit greater impulsivity and externalizing symptomatology relative to female adolescents. Furthermore, externalizing symptomatology has been associated with greater alcohol use and differential anterior insula functioning. The current longitudinal study on adolescents examined whether activity in the anterior insula, when processing uncertain outcomes and representing risk, is directly associated with gender differences in later adolescent alcohol use frequency, as well as indirectly through externalizing symptomatology.

METHOD

Using functional magnetic resonance imaging, we examined whether gender moderated these associations in a sample of 161 adolescents (53% male) with repeated annual measurements over 3 years. We monitored responding of a region implicated in risk processing during an economic lottery choice task involving uncertain outcomes. Self-reported externalizing symptomatology and alcohol use frequency were collected at all time points.

RESULTS

Results indicated that there was a significant indirect effect of anterior insula processing during the task at Time 1 on alcohol use at Time 3 through externalizing symptomatology at Time 2 for male, but not female, adolescents. Externalizing symptomatology predicted alcohol use for both male and female adolescents.

CONCLUSIONS

The findings suggest gender differences in vulnerability to later alcohol use, specifically in terms of how a neurobiological susceptibility to risk insensitivity may disproportionately influence male adolescents' externalizing symptomatology. Male adolescents who do not effectively integrate risk-related signals are likely to engage in externalizing behaviors, which in turn are related to later alcohol use. Findings also suggest differential roles of risk-related brain function that contribute to gendered pathways to adolescent health-risk behaviors.

Emotional Androgyny: A Preventive Factor of Psychosocial Risks at Work?

Although previous studies have acknowledged the connections between gender and emotional competences, more research is needed on how gender and emotion interact to influence psychosocial risks at work. This paper addresses how gender stereotypes and emotions simultaneously act as psychosocial antecedents of organizational stress. Following the principles of psychological androgyny, we propose that a combination of communion and agency can serve as a preventive factor at work and lead to healthier responses by providing a wider range of emotional competences to deal with organizational demands. Following previous methodological approaches, we include a quantitative review about scientific research on occupational health in the PsycINFO database during the period 1980-2017 from a multidimensional gender perspective that differentiates between studies addressing the topic from either sex, gender or gender identity dimensions. Finally, we propose new analytical directions to deal with psychosocial hazards at work by underscoring some of the complex ways in which gender and emotional competences influence psychosocial risks at work.

Females Are More Sensitive to Opponent's Emotional Feedback: Evidence From Event-Related Potentials

It is widely believed that females outperformed males in emotional information processing. The present study tested whether the female superiority in emotional information processing exists in a naturalistic social-emotional context, if so, what the temporal dynamics underlies. The behavioral and electrophysiological responses were recorded while participants were performing an interpersonal gambling game with opponents' facial emotions given as feedback. The results yielded that emotional cues modulated the influence of monetary feedback on outcome valuation. Critically, this modulation was more conspicuous in females: opponents' angry expressions increased females' risky tendency and decreased the amplitude of reward positivity (RewP) and feedback P300. These findings indicate that females are more sensitive to emotional expressions in real interpersonal interactions, which is manifested in both early motivational salience detection and late conscious cognitive appraisal stages of feedback processing.

Effects of Valence on Hemispheric Specialization for Emotion Word Processing

The use of emotion in language is a key element of human interactions and a rich area for cognitive research. The present study examined reactions to words of five types: positive emotion (e.g., happiness), negative emotion (e.g., hatred), positive emotion-laden (e.g., blessing), negative emotion-laden (e.g., prison), and neutral (e.g., chance). Words and nonwords were intermixed in a lexical decision task using hemifield presentation. Results revealed a general left hemisphere advantage. Overall, reaction times for positive words were faster than for negative or neutral words and this effect varied by hemifield of presentation. These results support a valence hypothesis of specialized processing in the left hemisphere of the brain for positive emotions and the right hemisphere for negative emotions.

Sex differences in the functional lateralization of emotion and decision making in the human brain

Dating back to the case of Phineas Gage, decades of neuropsychological research have shown that the ventromedial prefrontal cortex (vmPFC) is crucial to both real-world social functioning and abstract decision making in the laboratory (see, e.g., Stuss et al., ; Bechara et al., 1994; Damasio et al., ). Previous research has shown that the relationship between the laterality of individuals' vmPFC lesions and neuropsychological performance is moderated by their sex, whereby there are more severe social, emotional, and decision-making impairments in men with right-side vmPFC lesions and in women with left-side vmPFC lesions (Tranel et al., 2005; Sutterer et al., 2015). We conducted a selective review of studies examining the effect of vmPFC lesions on emotion and decision making and found further evidence of sex-related differences in the lateralization of function not only in the vmPFC but also in other neurological structures associated with decision making and emotion. This Mini-Review suggests that both sex and laterality effects warrant more careful consideration in the scientific literature. © 2016 Wiley Periodicals, Inc.

Sex in Context: Limitations of Animal Studies for Addressing Human Sex/Gender Neurobehavioral Health Disparities

Many brain and behavioral disorders differentially affect men and women. The new National Institutes of Health requirement to include both male and female animals in preclinical studies aims to address such health disparities, but we argue that the mandate is not the best solution to this problem. Sex differences are highly species-specific, tied to the mating system and social ecology of a given species or even strain of animal. In many cases, animals poorly replicate male-female differences in brain-related human diseases. Sex/gender disparities in human health have a strong sociocultural component that is intimately entangled with biological sex and challenging to model in animals. We support research that investigates sex-related variables in hypothesis-driven studies of animal brains and behavior. However, institutional policies that require sex analysis and give it special salience over other sources of biological variance can distort research. We caution that the costly imposition of sex analysis on nearly all animal research entrenches the presumption that human brain and behavioral differences are largely biological in origin and overlooks the potentially more powerful social, psychological, and cultural contributors to male-female neurobehavioral health gaps.

Lateralization for Processing Facial Emotions in Gay Men, Heterosexual Men, and Heterosexual Women

This study tested whether male sexual orientation and gender nonconformity influenced functional cerebral lateralization for the processing of facial emotions. We also tested for the effects of sex of poser and emotion displayed on putative differences. Thirty heterosexual men, 30 heterosexual women, and 40 gay men completed measures of demographic variables, recalled childhood gender nonconformity (CGN), IQ, and the Chimeric Faces Test (CFT). The CFT depicts vertically split chimeric faces, formed with one half showing a neutral expression and the other half showing an emotional expression and performance is measured using a "laterality quotient" (LQ) score. We found that heterosexual men were significantly more right-lateralized when viewing female faces compared to heterosexual women and gay men, who did not differ significantly from each other. Heterosexual women and gay men were more left-lateralized for processing female faces. There were no significant group differences in lateralization for male faces. These results remained when controlling for age and IQ scores. There was no significant effect of CGN on LQ scores. These data suggest that gay men are feminized in some aspects of functional cerebral lateralization for facial emotion. The results were discussed in relation to the selectivity of functional lateralization and putative brain mechanisms underlying sexual attraction towards opposite-sex and same-sex targets.

Voluntary and involuntary emotional memory following an analogue traumatic stressor: the differential effects of communality in men and women

BACKGROUND

Men and women show differences in performance on emotional processing tasks. Sex also interacts with personality traits to affect information processing. Here we examine effects of sex, and two personality traits that are differentially expressed in men and women - instrumentality and communality - on voluntary and involuntary memory for distressing video-footage.

METHODS

On session one, participants (n = 39 men; 40 women) completed the Bem Sex-Role Inventory, which assesses communal and instrumental traits. After viewing film-footage of death/serious injury, participants recorded daily involuntary memories (intrusions) relating to the footage on an online diary for seven days, returning on day eight for a second session to perform a voluntary memory task relating to the film.

RESULTS

Communality interacted with sex such that men with higher levels of communality reported more frequent involuntary memories. Alternatively, a communality × sex interaction reflected a tendency for women with high levels of communality to perform more poorly on the voluntary recognition memory task.

LIMITATIONS

The study involved healthy volunteers with no history of significant psychological disorder. Future research with clinical populations will help to determine the generalizability of the current findings.

CONCLUSION

Communality has separate effects on voluntary and involuntary emotional memory. We suggest that high levels of communality in men and women may confer vulnerability to the negative effects of stressful events either through the over-encoding of sensory/perceptual-information in men or the reduced encoding of contextualised, verbally-based, voluntarily accessible representations in women.

Individual differences in emotion lateralisation and the processing of emotional information arising from social interactions

Previous research examining the possible association between emotion lateralisation and social anxiety has found conflicting results. In this paper two studies are presented to assess two aspects related to different features of social anxiety: fear of negative evaluation (FNE) and emotion regulation. Lateralisation for the processing of facial emotion was measured using the chimeric faces test. Individuals with greater FNE were more strongly lateralised to the right hemisphere for the processing of anger, happiness and sadness; and, for the processing of fearful faces the relationship was found for females only. Emotion regulation strategies were reduced to two factors: positive strategies and negative strategies. For males, but not females, greater reported use of negative emotion strategies is associated with stronger right hemisphere lateralisation for processing negative emotions. The implications for further understanding the neuropsychological processing of emotion in individuals with social anxiety are discussed.

Masculinity/femininity predicts brain volumes in normal healthy children

Previous research has shown sex differences in brain morphology ( De Bellis et al., 2001 ). However, these studies have not taken gender into account. Gender is a phenotype that describes behavior. In this study, we examined the relationship between gender, sex, and brain volumes in children. One hundred and eight children ages 7 to 17 were administered the Children's Sex Role Inventory ( Boldizar, 1991 ) and obtained volumetric brain data via magnetic resonance imaging (MRI). We found that, in the frontal lobe, higher masculinity predicted greater volumes of white matter. Also, in the temporal lobe, higher femininity predicted greater volumes of gray matter.

Age-related differences in cortical activity during a visuo-spatial working memory task with facial stimuli

Emotion, importantly displayed by facial expressions, is one of the most significant memory modulators. The interaction between memory and the different emotional valences change across lifespan, while young adults (YA) are expected to better recall negative events (Negativity Bias Hypothesis), older adults (OA) tend to focus on positive stimuli (Positivity Effect Hypothesis). This research work aims at verifying whether cortical electrical activity of these two age groups would also be differently influenced by emotional valences in a visuo-spatial working memory task. 27 YA (13 males) and 25 OA (14 males), all healthy volunteers, underwent electroencephalographic recordings (21 scalp electrodes montage), while performing the Spatial Delayed Recognition Span Task using a touch screen with different stimuli categories: neutral, positive and negative faces and geometric pictures. YA obtained higher scores than OA, and showed higher activation of theta and alpha bands in the frontal and midline regions, besides a more evident right-hemispheric asymmetry on alpha band when compared to OA. For both age groups, performance in the task was worse for positive faces than to negative and to neutral faces. Facial stimuli induced a better performance and higher alpha activation on the pre-frontal region for YA, and on the midline, occipital and left temporal regions for OA when compared to geometric figures. The superior performance of YA was expected due to the natural cognitive deficits connected to ageing, as was a better performance with facial stimuli due to the evolutionary importance of faces. These results were related to cortical activity on areas of importance for action-planning, decision making and sustained attention. Taken together, they are in accordance with the Negativity Bias but do not support the Positivity Effect. The methodology used was able to identify age-related differences in cortical activity during emotional mnemonic processing and may be interesting to future investigations.

Sex-differences of face coding: evidence from larger right hemispheric M170 in men and dipole source modelling

The processing of faces relies on a specialized neural system comprising bilateral cortical structures with a dominance of the right hemisphere. However, due to inconsistencies of earlier findings as well as more recent results such functional lateralization has become a topic of discussion. In particular, studies employing behavioural tasks and electrophysiological methods indicate a dominance of the right hemisphere during face perception only in men whereas women exhibit symmetric and bilateral face processing. The aim of this study was to further investigate such sex differences in hemispheric processing of personally familiar and opposite-sex faces using whole-head magnetoencephalography (MEG). We found a right-lateralized M170-component in occipito-temporal sensor clusters in men as opposed to a bilateral response in women. Furthermore, the same pattern was obtained in performing dipole localization and determining dipole strength in the M170-timewindow. These results suggest asymmetric involvement of face-responsive neural structures in men and allow to ascribe this asymmetry to the fusiform gyrus. This specifies findings from previous investigations employing event-related potentials (ERP) and LORETA reconstruction methods yielding rather extended bilateral activations showing left asymmetry in women and right lateralization in men. We discuss our finding of an asymmetric fusiform activation pattern in men in terms of holistic face processing during face evaluation and sex differences with regard to visual strategies in general and interest for opposite faces in special. Taken together the pattern of hemispheric specialization observed here yields new insights into sex differences in face perception and entails further questions about interactions between biological sex, psychological gender and influences that might be stimulus-driven or task dependent.

Is It a Baby? Perceived Age Affects Brain Processing of Faces Differently in Women and Men

It is known that infant faces stimulate visual and anterior brain regions belonging to the mesocortical limbic system (orbito-frontal cortex, anterior cingulate cortex, and nucleus accumbens) as well as the fusiform gyrus during face coding, suggesting a preferential response to baby schema. In the present investigation, faces of infants, children, and adults were presented to 40 male and female right-handed university students with technological objects (and inanimate scenarios to serve as targets) in a randomly mixed fashion. EEG was recorded from 128 scalp sites. In both sexes, the N1 response to infant faces was larger than the response to adult faces; however, the baby-specific N1 response was much larger in women than in men across the left hemisphere. The anterior N2 response to infants was greater than the response to children only in women, whereas the response to children of any age was larger than the response to adults in men. LORETA identified the intracranial sources of N2 response to infants in the left fusiform gyrus (FG), as well as the uncus, cingulate, and orbito-frontal cortices. The FG, the limbic, and especially the orbito-frontal sources were much larger in women than in men. The data suggest a sex difference in the brain response to faces of different ages and in the preferential response to infants, especially with regard to activation of the mesocorticolimbic system.