Judgements of attractiveness of the opposite sex and nostril differences in self-rated mood: The effects of androstenol.

Androstenol has been reported to influence judgements of attractiveness and to affect participants' mood. In the present study, participants were asked to sniff androstenol or a control odour (pure ethanol) unilaterally with the left or right nostril. Subsequently, they rated the attractiveness of photographs of the opposite sex and their own feelings on four mood scales. Participants rated the photographs as significantly more attractive after sniffing androstenol compared with the control odour. This did not depend upon androstenol being perceived as pleasant. Androstenol made male participants feel more lively, and both male and female participants more sexy, when sniffed through the right compared with the left nostril. Participants rated themselves as more irritable and aggressive when exposed to androstenol through the left nostril. The findings are discussed in relation to the effects of arousal on attraction and in the context of current theories of hemispheric differences in emotion.

Repeatability of lateralisation in mosquitofish Gambusia holbrooki despite evidence for turn alternation in detour tests.

Akin to handedness in humans, some animals show a preference for moving to the left or right. This is often attributed to lateralised cognitive functions and eye dominance, which, in turn, influences their behaviour. In fishes, behavioural lateralisation has been tested using detour mazes for over 20 years. Studies report that certain individuals are more likely to approach predators or potential mates from one direction. These findings imply that the lateralisation behaviour of individuals is repeatable, but this is rarely confirmed through multiple testing of each individual over time. Here we quantify the repeatability of turning behaviour by female mosquitofish (Gambusia holbrooki) in a double sided T-maze. Each female was tested three times in each of six treatments: when approaching other females, males, or an empty space; and when able to swim freely or when forced to choose by being herded from behind with a net. Although there was no turning bias based on the mean population response, we detected significant repeatability of lateralisation in five of the six treatments (R = 0.251-0.625). This is noteworthy as we also found that individuals tended to alternate between left and right turns, meaning that they tend to move back and forth along one wall of the double-sided T-maze. Furthermore, we found evidence for this wall following when re-analysing data from a previous study. We discuss potential explanations for this phenomenon, and its implications for study design.

An examination of the influence of prenatal sex hormones on handedness: Literature review and amniotic fluid data.

Competing theories have posited roles for foetal androgen exposure in the development of human handedness. However, due to practical and ethical considerations, few studies have used hormonal measures to examine this possibility. The current paper reviews this literature and reveals a generally inconsistent pattern of results. We also present data from a longitudinal study of prenatal sex hormone exposure and subsequent handedness. More specifically, we examine correlations between testosterone and estradiol measured from second trimester amniotic fluid and hand preference (Dutch language version of the Edinburgh Handedness Inventory) and hand skill asymmetry (pegboard task) measured at 15 years of age. Prenatal sex hormone exposure was not associated with the direction of hand preference in either males or females. However, in females, high levels of prenatal testosterone were associated with weaker lateralisation of hand skill, and high levels of prenatal estradiol were associated with weaker hand preference. In addition, high levels of prenatal testosterone were associated with increased task duration (i.e., slow hand speed) for the right and left hands of males. The pattern of results observed here is not entirely consistent with any of the main theories linking sex hormones with handedness, suggesting that an association between these variables may be more complex than initially thought.

Can cerebral lateralisation explain heterogeneity in language and increased non-right handedness in autism? A literature review.

BACKGROUND: Autism is characterised by phenotypic variability, particularly in the domains of language and handedness. However, the source of this heterogeneity is currently unclear. AIMS: To synthesise findings regarding the relationship between language, handedness, and cerebral lateralisation in autistic people and consider how future research should be conducted in order to progress our understanding of phenotypic variability. METHODS AND PROCEDURES: Following a literature search and selection process, 19 papers were included in this literature review. Studies using behavioural, structural, and functional measures of lateralisation are reviewed. OUTCOMES AND RESULTS: The studies reviewed provided consistent evidence of differential cerebral lateralisation in autistic people, and this appears to be related to between-group differences in language. Evidence relating this to handedness was less consistent. Many of the studies did not include heterogeneous samples, and/or did not specify the language process they investigated. CONCLUSIONS AND IMPLICATIONS: This review suggests that further research is needed to fully understand the relationship between cerebral lateralisation and phenotypic variability within autism. It is crucial that future studies in this area include heterogeneous samples, specify the language process they are investigating, and consider taking developmental trajectories into account.

No evidence for side preference or handedness in a New Zealand rail species with habitual foot-usage, the pukeko.

Many animals show evidence of cerebral lateralisation, i.e. morphological differences and functional specialisation in two separate hemispheres of the brain. Laterality in behaviour is commonly used as an indicator of cerebral lateralisation, as asymmetry in actions often mirrors asymmetry in the brain. It has been predicted that species that habitually use limbs to manipulate food or resources will develop strong limb preferences, and data in a limited set of taxa support this prediction. However, relatively few species have been studied, limiting our understanding of how taxonomically widespread such behavioural asymmetries might be, and thus how such preferences evolve. Here, we test for limb preference within a new taxon, the rails, using the pukeko (Porphyrio p. melanotus), a species that frequently uses its feet while feeding. We quantified foot-use of 359 individual pukeko and found that though some individuals show preferences, there was no overall side preference at the population level - roughly equal numbers of individuals showed a left preference, a right preference, or no preference, though we detected a weak preference in adults during long-use behaviours. We also found that the strength of side preference weakened with increased observations of foot-usage. Finally, though patterns were similar when looking at brief and longer foot uses, the within-individual relationships between preference in those contexts was only significant in birds that used their feet at least five times. Together these findings question whether habitual foot use will lead to side preference and suggest that the apparent wide-spread and prevalent nature of this pattern in current literature may be due to a publication bias rather than the general presence of a relationship. Studies that cover a great taxonomic spread are needed.

It's in the eye of the beholder: visual lateralisation in response to the social environment in poeciliids.

The social environment offers fish complex information about the quality, performance, personality and other cues of potential mates and competitors simultaneously. It is likely, therefore, that the environmental information regarding the context of mate choice is perceived and processed differently in species and sexes in respect to lateralisation. The present study comparatively assessed visual lateralisation behaviour in response to different social or sexual stimuli in three closely related poeciliid species (P. latipinna, P. mexicana, P. formosa) in comparison to a more distantly related species (P. reticulata). Individuals were presented with four different social or sexual stimuli that were tested against a control stimulus; (a) a conspecific male, (b) a conspecific female, (c) a heterosexual conspecific pair, (d) three conspecific females (shoal). In order to approach a target stimulus, focal fish had to perform detours to the right or left of a vertically straight-shaped barrier. The three closely related poeciliid species, P. latipinna, P. mexicana, P. formosa, appeared to have a general tendency to turn right (i.e., left-eye preference), whereas the more distantly related P. reticulata males and females showed an overall bias to the left (i.e., right-eye preference) in response to various social-sexual incitements. Moreover, body size seemed to significantly influence especially the males' detour behaviour, with smaller males acting in opposition to their larger conspecifics in response to certain social stimuli. In this case, smaller and larger Poecilia spp. males responded in the same way as smaller and larger males of the other three poeciliid species. Therefore, results possibly point to differences in the degree of general social behaviour between closely and more distantly related species and mating motivation amongst larger and smaller individuals when placed in a novel social environment. Hence, present results possibly suggest a sex-specific functional lateralisation for the analysis of visual information and seem to support the closer ancestral relationships between the Poecilia spp. tested in this study and the more distantly related guppies in terms of their left-right lateralisation. Generally, present results suggest that functional asymmetries in behaviour could be widespread among vertebrates, thus supporting the hypothesis of an early evolution of lateralisation in brain and behaviour.

Human laterality for manipulation and gestural communication related to 60 everyday activities: Impact of multiple individual-related factors.

Literature on laterality emphasises the importance of implementing a comprehensive investigation of humans' and non-humans' laterality for both non-communication and communication functions. Adopting a global approach should enhance our understanding of the mechanistic drivers of human brain functional lateralisation and help to explore further the nature of the left-hemispheric systems for both functions. This study investigated human laterality for both functions by taking, for the first time, numerous behaviours and multiple potential influential factors into consideration. We analysed replies to the Rennes Laterality Questionnaire that takes into account simultaneously: participants' behavioural, demographic and social characteristics as well as their genetic/social learning components and collateral factors such as health problems. We collected and analysed a large data set including 450,220 item responses (317,594 items related to behavioural laterality and 132,626 items related to personal information) by 5904 participants. The majority of participants were right-lateralised for nine behavioural categories. The laterality of right-lateralised individuals for the behaviours considered varied very little between behavioural categories, contrary to the laterality of ambiguously- and left-lateralised individuals. This is the first evidence of the stability of right-lateralised individuals and the relative flexibility of ambiguously- and left-lateralised individuals with regards to behavioural laterality related to 60 everyday activities. Moreover, the laterality patterns of our study population were linked in particular to the following individual-related factors: demographic characteristics (current continent of residence), social characteristics (socio-professional group and study level), and collateral factors (writing hand, forced right-hand use, guiding eye, and health problems related to ear and back). We discuss our findings in relation to the evolutionary roots of human brain lateralisation for non-communication and communication functions.

Atypical speech lateralization in adults with developmental coordination disorder demonstrated using functional transcranial Doppler ultrasound.

Research using clinical populations to explore the relationship between hemispheric speech lateralization and handedness has focused on individuals with speech and language disorders, such as dyslexia or specific language impairment (SLI). Such work reveals atypical patterns of cerebral lateralization and handedness in these groups compared to controls. There are few studies that examine this relationship in people with motor coordination impairments but without speech or reading deficits, which is a surprising omission given the prevalence of theories suggesting a common neural network underlying both functions. We use an emerging imaging technique in cognitive neuroscience; functional transcranial Doppler (fTCD) ultrasound, to assess whether individuals with developmental coordination disorder (DCD) display reduced left-hemisphere lateralization for speech production compared to control participants. Twelve adult control participants and 12 adults with DCD, but no other developmental/cognitive impairments, performed a word-generation task whilst undergoing fTCD imaging to establish a hemispheric lateralization index for speech production. All participants also completed an electronic peg-moving task to determine hand skill. As predicted, the DCD group showed a significantly reduced left lateralization pattern for the speech production task compared to controls. Performance on the motor skill task showed a clear preference for the dominant hand across both groups; however, the DCD group mean movement times were significantly higher for the non-dominant hand. This is the first study of its kind to assess hand skill and speech lateralization in DCD. The results reveal a reduced leftwards asymmetry for speech and a slower motor performance. This fits alongside previous work showing atypical cerebral lateralization in DCD for other cognitive processes (e.g., executive function and short-term memory) and thus speaks to debates on theories of the links between motor control and language production.