A sex difference in turning bias in humans

Clockwise rotation of perspective view improves spatial recognition of complex environments in aging

Deciphering the human spatial cognition system involves the development of simple tasks to assess how our brain works with shapes and forms. Prior studies in the mental rotation field disclosed a clockwise rotation bias on how basic stimuli are perceived and processed. However, there is a lack of a substantial scientific background for complex stimuli and how factors like sex or aging could influence them. Regarding the latter point, it is well known that our spatial skills tend to decline as we grow older. Hence, the hippocampal system is especially sensitive to aging. These neural changes underlie difficulties for the elderly in landmark orientation or mental rotation tasks. Thus, our study aimed to check whether the effect of clockwise and anticlockwise rotations in the spatial recognition of complex environments could be modulated by aging. To do so, 40 young adults and 40 old adults performed the ASMRT, a virtual spatial memory recognition test. Results showed that young adults outperformed old adults in all difficulty conditions (i.e., encoding one or three boxes positions). In addition, old adults were affected more than young adults by rotation direction, showing better performance in clockwise rotations. In conclusion, our study provides evidence that aging is particularly affected by the direction of rotation. We suggest that clockwise bias could be linked with the cognitive decline associated with aging. Future studies could address this with brain imaging measures.

A study of turn bias in people with idiopathic Parkinson's disease

The objective of the study is to explore whether people with Parkinson's disease (PwPD) display a preferential turn bias dependent upon disease asymmetry, and whether specific disease features predict turn bias. PwPD and age-matched controls were instructed to walk on an instrumented gait mat making "normal" turns. Trials were analyzed using Proto Kinetics Movement Analysis Software (PKMAS) and time-locked video recordings to obtain turn directionality and spatiotemporal turn measures. Turn bias was estimated using previously defined formulas. Seventy-two PwPD and 28 controls were included. One hundred percent of controls and 85% of PwPD had left turn bias. Turn bias was not significantly associated with age, gender, handedness, disease asymmetry, cognition, or disease severity. The Freezing of Gait Questionnaire (FOGQ) questions 5 and 6 showed linear-by-linear association with turn bias. In binary logistic and ordinal regression models, FOGQ question 6 (average duration of turn freezing) and turn width were predictive of turn bias. Rightward turns had greater frequency of freezing episodes. Turn bias in our PwPD cohort does not appear related to disease asymmetry or other disease features, except gait freezing. Whether freezing severity on turning leads to non-left turn bias or vice versa requires more focused studies. Physical therapy interventions targeting turning direction in PwPD could reduce freezing severity.

The right way to kiss: directionality bias in head-turning during kissing

Humans have a bias for turning to the right in a number of settings. Here we document a bias in head-turning to the right in adult humans, as tested in the act of kissing. We investigated head-turning bias in both kiss initiators and kiss recipients for lip kissing, and took into consideration differences due to sex and handedness, in 48 Bangladeshi heterosexual married couples. We report a significant male bias in the initiation of kissing and a significant bias in head-turning to the right in both kiss initiators and kiss recipients, with a tendency among kiss recipients to match their partners’ head-turning direction. These interesting outcomes are explained by the influences of societal learning or cultural norms and the potential neurophysiological underpinnings which together offer novel insights about the mechanisms underlying behavioral laterality in humans.

Directional Preferences in Turning Behavior of Girls and Boys

Turning biases in humans and animals are known to be related to dopaminergic asymmetry between the brain hemispheres. A laboratory method, in which turning preference was evaluated, was adapted based upon the turning of the subject toward a particular sound in a square room. One of the aims of this study was to investigate the reliability of this method with children, and the other aim was to research the turning preference in boys and girls. 31 children between 7 and 13 yr. old volunteered as subjects, and 17 subjects were retested. The subjects tended significantly to turn leftward (60.1%), and fewer girls (53.7%) turned to the left than boys (66.2%). The correlation between the test and the retest was significant ( r = .79, p < .01). Most studies have indicated that humans in childhood and adulthood exhibit left-turning preference, but conflicts between the results obtained on different types of rotation tasks have suggested that hemispheric dopaminergic activity might affect preference. That needs study.

Anticlockwise or clockwise? A dynamic Perception-Action-Laterality model for directionality bias in visuospatial functioning

Orientation bias and directionality bias are two fundamental functional characteristics of the visual system. Reviewing the relevant literature in visual psychophysics and visual neuroscience we propose here a three-stage model of directionality bias in visuospatial functioning. We call this model the 'Perception-Action-Laterality' (PAL) hypothesis. We analyzed the research findings for a wide range of visuospatial tasks, showing that there are two major directionality trends in perceptual preference: clockwise versus anticlockwise. It appears these preferences are combinatorial, such that a majority of people fall in the first category demonstrating a preference for stimuli/objects arranged from left-to-right rather than from right-to-left, while people in the second category show an opposite trend. These perceptual biases can guide sensorimotor integration and action, creating two corresponding turner groups in the population. In support of PAL, we propose another model explaining the origins of the biases - how the neurogenetic factors and the cultural factors interact in a biased competition framework to determine the direction and extent of biases. This dynamic model can explain not only the two major categories of biases in terms of direction and strength, but also the unbiased, unreliably biased or mildly biased cases in visuosptial functioning.

Reproductive Steroid Regulation of Mood and Behavior

In this article, we examine evidence supporting the role of reproductive steroids in the regulation of mood and behavior in women and the nature of that role. In the first half of the article, we review evidence for the following: (i) the reproductive system is designed to regulate behavior; (ii) from the subcellular to cellular to circuit to behavior, reproductive steroids are powerful neuroregulators; (iii) affective disorders are disorders of behavioral state; and (iv) reproductive steroids affect virtually every system implicated in the pathophysiology of depression. In the second half of the article, we discuss the diagnosis of the three reproductive endocrine-related mood disorders (premenstrual dysphoric disorder, postpartum depression, and perimenopausal depression) and present evidence supporting the relevance of reproductive steroids to these conditions. Existing evidence suggests that changes in reproductive steroid levels during specific reproductive states (i.e., the premenstrual phase of the menstrual cycle, pregnancy, parturition, and the menopause transition) trigger affective dysregulation in susceptible women, thus suggesting the etiopathogenic relevance of these hormonal changes in reproductive mood disorders. Understanding the source of individual susceptibility is critical to both preventing the onset of illness and developing novel, individualized treatments for reproductive-related affective dysregulation. © 2016 American Physiological Society. Compr Physiol 6:1135-1160, 2016e.

Childrens' left-turning preference is not modulated by magical ideation

The literature on human turning preferences is inconsistent. While the few studies with children below 14 years of age uniformly describe an overall left-turning (counterclockwise) tendency, a recent Internet study with more than 1500 adults found a right-sided (clockwise) bias. We set out to investigate spontaneous turning behaviour in children age 5-3 years and, based on neuropsychiatric work in adults, also explored a potential association with magical thinking. Findings indicated a clear left-turning preference, independent of a participant's sex and handedness. Whether a child responded a question about the existence of extrasensory communication in the affirmative or not was unrelated to direction and size of turning bias and lateral preference. Our results are consistent with a left-sided turning preference reported for children, but in opposition to the clockwise bias recently described in a large-scale study with adults. Whether they point to a maturational gradient in the preferred direction of spontaneous whole-body rotation or rather to a lack of comparability between measures used in observational versus Internet-based studies remains to be further investigated. Regarding a purported association between body turns and magical thinking, our study is preliminary, as only one single question was used to probe the latter.

The effect of stopping before turning on the direct observational measure of whole body turning bias

Turning bias, the preferential tendency to turn toward a given direction has been reported in both rodents and human participants. The observational gait method of determining turning bias in humans requires a stop prior to turning. This study removed the stop and hypothesised that turning bias would remain the same between stop and non-stop conditions if bias was solely under the control of neurochemical asymmetries. The results showed that statistically turning bias remained the same (to the left) regardless of method used but there was no agreement between the methods thus rejecting the hypothesis. It is likely that when not stopping biomechanical factors related to gait when turning influence the direction of turn rather than solely neurochemical asymmetries.

Laterality effects in the spinning dancer illusion: The viewing-from-above bias is only part of the story

The 'silhouette illusion', representing the silhouette of a female dancer pirouetting about her vertical axis, is a bistable stimulus created by Japanese web designer Nobuyuki Kayahara. Although the dancer can be perceived as spinning either clockwise or counterclockwise, the clockwise rotation is usually preferred. Troje and McAdam (i-Perception, 2010, 1, 143) showed that this clockwise bias can be attributed to the tendency to assume a viewpoint from above rather than from below, given that the dancer is portrayed from a vantage point that is not perpendicular to the axis of rotation. Here, we tested whether another possible factor contributing to the observers' interpretation of this bistable stimulus might be the tendency to perceive movements of the right rather than the left foot. We confirmed both the viewing-from-above bias and our hypothesis. The bias to perceive movements of the right leg might be a generalization to lower limbs of a perceptual frequency effect already observed for upper limbs. Such a perceptual and attentional bias towards the right hand/foot could account for the greater ability to predict the outcome of sport actions when observing right- rather than left-limbed movements, and thus the left-handers' and left-footers' advantage observed in a variety of interactive sports.

The significance of hand dominance in hip osteoarthritis

OBJECTIVES

Hip arthroplasty registries, encompassing all-cause end-stage hip degeneration, have shown that slightly more right hip replacements are performed than left. Given that greater than 85% of individuals are right-handed, we sought to investigate the association between side of hand dominance and side of hip osteoarthritis.

METHODS

This Level III observational study evaluated exclusively end-stage osteoarthritis of the hip, using 3 independent centres totalling 386 consecutive arthroplasty patients. Logistic regression was used as a statistical model.

RESULTS

In total, 322 patients with hip osteoarthritis were included in the final analysis, including 146 (45.5%) women and 176 (54.5%) men, with a mean age of 68.1 years (SD = 9.5 years). There were 133 (41.2%) right, 73 (22.6%) left, and 116 (35.9%) bilateral hips where the contralateral side had been previously replaced. The proportion of individuals requiring unilateral hip arthroplasty on their dominant side was 67.4%.

CONCLUSIONS

In the development of hip osteoarthritis, one is significantly more likely to require hip arthroplasty on their dominant side than in the contralateral hip. Assessment of hand dominance identifies cerebral laterality as a contributing factor in predisposing one's dominant side to hip osteoarthritis.

Turning bias in virtual spatial navigation: age-related differences and neuroanatomical correlates

Rodents frequently exhibit rotational bias associated with asymmetry in lesions and neurotransmitters in the striatum. However, in humans, turning preference is inconsistent across studies, and its neural correlates are unclear. We examined turning bias in 140 right-handed healthy adults (18-77 years old), who navigated a virtual Morris Water Maze. On magnetic resonance images, we measured volumes of brain regions relevant to spatial navigation. We classified turns that occurred during virtual navigation as veering (less than 10°), true turns (between 10° and 90°) and course reversals (over 90°). The results showed that performance (time of platform search and distance traveled) was negatively related to age. The distance traveled was positively associated with volume of the orbito-frontal cortex but not with the volumes of the cerebellum, the hippocampus or the primary visual cortex. Examination of turning behavior showed that all participants veered to the right. In turns and reversals, although on average there was no consistent direction preference, we observed significant individual biases. Virtual turning preference correlated with volumetric asymmetry in the striatum, cerebellum, and hippocampus but not in the prefrontal cortex. Participants preferred to turn toward the hemisphere with larger putamen, cerebellum and (in younger adults only) hippocampus. Advanced age was associated with greater rightward turning preference. Men showed greater leftward preference whereas women exhibited stronger rightward bias.

Hemispheric specialization varies with EEG brain resting states and phase of menstrual cycle

A growing body of behavioral studies has demonstrated that women’s hemispheric specialization varies as a function of their menstrual cycle, with hemispheric specialization enhanced during their menstruation period. Our recent high-density electroencephalogram (EEG) study with lateralized emotional versus neutral words extended these behavioral results by showing that hemispheric specialization in men, but not in women under birth-control, depends upon specific EEG resting brain states at stimulus arrival, suggesting that hemispheric specialization may be pre-determined at the moment of the stimulus onset. To investigate whether EEG brain resting state for hemispheric specialization could vary as a function of the menstrual phase, we tested 12 right-handed healthy women over different phases of their menstrual cycle combining high-density EEG recordings and the same lateralized lexical decision paradigm with emotional versus neutral words. Results showed the presence of specific EEG resting brain states, associated with hemispheric specialization for emotional words, at the moment of the stimulus onset during the menstruation period only. These results suggest that the pre-stimulus EEG pattern influencing hemispheric specialization is modulated by the hormonal state.

Hand clasping, arm folding, and handedness: relationships and strengths of preference

We investigated via a survey the relationship between hand clasping, arm folding, and handedness. We aimed to provide new data on degree of preference for each of these lateralities. We also examined the relative importance of thumb position versus interdigitisation of the fingers in determining one's comfort in a hand-clasping position. We explored this in the context of the fact that sensory acuity is greater for the thumb than other fingers, suggesting that preference for how the fingers are intermeshed may be more influenced by thumb than finger position. Lastly we performed an exploratory analysis to determine if self-reported menstrual phase-known to influence turning bias-also influences hand clasping, arm folding or the strength of one's handedness. Our study suggests that lateral preferences for hand clasping, arm folding, and handedness are independent. However, the degrees of lateral preference for hand clasping and arm folding are correlated. Our exploration of the relative importance of thumbs versus fingers to hand clasping revealed some trends that were not statistically significant, but worth future exploration. Our data on menstrual phase showed a reduced strength of preference for arm folding in mid-luteal females versus non-mid-luteal females.

Test–retest stability of an experimental measure of human turning behaviour in right-handers, mixed-handers, and left-handers

Animals turn away from the hemisphere with the more active dopamine (DA) system. For humans, a similar relationship has been assumed, albeit that side preferences obtained from different measures are inconsistent. Given the important role of DA on human behaviour and cognition, a stable human turning measure is of significant experimental value. We assessed the stability (test and retest 4 weeks apart) of veering behaviour (lateral deviations during blindfolded straight ahead walking) in 20 healthy right-handers, 20 mixed-handers, and 20 left-handers. Veering behaviour did not differ between groups, and did not reveal any particular side preference in any group. Relationships of side preferences between testing sessions for the different handedness groups was low for right-handers, and showed some minor consistency for the mixed-handed group. Neither handedness nor footedness was significantly related to preferred veering side. These findings, if not related meaningfully to DA-mediated conditions (e.g., clinical populations, pharmacological studies, personality) in the future, suggests that veering behaviour is an inappropriate alternative to the animal turning model. These findings challenge the reliability of human turning measures, and invite more broadly for a critical evaluation of turning measures as an indicator of hemispheric DA asymmetries in human populations.

Turning bias and lateral dominance in a sample of able-bodied and amputee participants

Turning bias is the tendency to turn towards a given direction. Conflicting results from previous studies suggest that a number of factors may influence turning direction. The aim of this study was to determine if biomechanical asymmetries influence turning bias. A total of 100 able-bodied participants, and 30 trans-tibial amputees who, by definition, possess a functional asymmetry, volunteered to participate in the study. The right hand and right foot were significantly dominant for the able-bodied sample. Able-bodied participants showed a significant turning preference towards the left, which was opposite to the dominant hand and foot. The amputees were significantly right-hand dominant and the side of the amputation influenced foot dominance. The amputee sample showed no preferred turning direction. Turning bias indices in the amputee sample were not significantly associated with handedness, footedness, side of amputation, or dominance prior to amputation. The lack of a preferred direction of turn in the amputee sample suggests that biomechanical asymmetries can influence turning bias.

Intrinsic and extrinsic factors of turning preferences in humans

Turning behaviour in 107 adolescents was observed during walking and running under different temporal and biomechanical constraints. Participants ran and walked back and forth between two lines 9.5m apart in a neutral environment. All of the turns that the participants made to change direction between the lines were videotaped. A general preference for turning leftwards was observed with the percentage being higher in the unconstrained running condition when compared to the walking condition (71% versus 59%, respectively). This intrinsic preference was easily overruled when positional constraints on the starting position were imposed. Such positional constraints did not, however, suppress the intrinsic directional bias observed during running. It is concluded that turning preference in humans is the result of a complex interaction between intrinsic preferences and externally imposed task constraints.

Optic flow dominates visual scene polarity in causing adaptive modification of locomotor trajectory

Locomotion and posture are influenced and controlled by vestibular, visual and somatosensory information. Optic flow and scene polarity are two characteristics of a visual scene that have been identified as being critical in how they affect perceived body orientation and self motion. The goal of this study was to determine the role of optic flow and visual scene polarity on adaptive modification in locomotor trajectory. An object is said to have visual polarity, or to be "visually polarized", when it contains an identifiable principal axis with one end distinct from the other. Two computer-generated virtual reality scenes were shown to subjects during 20 min of treadmill walking. One scene was a highly polarized scene, while the other was composed of objects displayed in a non-polarized fashion. Both virtual scenes depicted constant rate self motion equivalent to walking counterclockwise around the perimeter of a room. Subjects performed Stepping Tests blindfolded before and after scene exposure to assess adaptive changes in locomotor trajectory. Subjects showed a significant difference in heading direction, between pre- and post-adaptation Stepping Tests, when exposed to either scene during treadmill walking. However, there was no significant difference in the subjects' heading direction between the two visual scene polarity conditions. Therefore, it was inferred from these data that optic flow has a greater role than visual polarity in influencing adaptive locomotor function.

Urinary dopamine and turn bias in traumatized women with and without PTSD symptoms

Turning biases are known to occur in the direction of the brain hemisphere with decreased dopamine (DA). Although elevations in urinary DA have been shown in posttraumatic stress disorder (PTSD), evidence for dysregulation of dopaminergic activity in the brain is lacking. Turn bias and urinary DA levels were examined in mothers of childhood cancer survivors. As expected, cancer trauma mothers with PTSD symptoms (n=14) had higher urinary DA levels than trauma mothers without PTSD symptoms (n=7) and controls (n=8) (P=0.01). Groups were also significantly different in prevalence of left turn bias (P=0.03). All controls (100%) showed a left turn bias compared to 75 and 37.5% prevalence among trauma mothers with and without PTSD, respectively. Urinary DA levels and turn bias rates were not correlated. Results lend support for further exploration of DA in traumatized groups with and without PTSD.

Cross-species investigations of prenatal experience, hatching behavior, and postnatal behavioral laterality

Turning biases have been reported in some mammalian species, but less is known about such biases in nonmammalians. This study investigated turning biases in domestic chicks, bobwhite and Japanese quail, leopard geckos, and snapping turtles. Domestic chicks (white leghorn and bantam) and bobwhite quail demonstrate strong group laterality. Japanese quail chicks, snapping turtles, and leopard geckos demonstrate no significant group bias. Results are discussed with regard to differences in embryonic experience, hatching behavior, and postnatal environment.

The relationship between handedness and fine motor performance

The aim of this study was to re-investigate the relationship between handedness and asymmetry in hand performance, and the sex difference in motor asymmetry. Three-hundred and ten medical students volunteered as subjects. Handedness was assessed by a 13-item questionnaire adapted from Chapman and Chapman. Fine motor performance was measured using a finger tapping task. In this task, subjects were required to tap as rapidly as possible with their index finger on a mouse button for a period of 10 s. There was a significant correlation between handedness scores and the scores of the finger tapping task. In the total sample, the correlation between hand speed and the handedness score indicated that the distribution of hand preference is associated with left hand speed, but not right hand speed. Results confirmed that right-handed females tend to have more asymmetric motor function than right-handed males.

The effect of familial sinistrality on the relation between schizophrenialike thinking and pseudoneglect

We have recently reported a correlation between schizophrenialike symptoms and the degree of pseudoneglect in healthy right-handers. We aimed to investigate the effect of familial sinistrality (FS) on this relation. Seventy-six healthy right-handers were divided into four groups on the basis of gender and FS. A computerized version of Corsi's task was used as the visuospatial task. Subjects filled in the Magical Ideation Scale (MI), which asked for delusionlike beliefs, and performed the Corsi's task using each hand. Performance of both hemispaces was separately evaluated. In all groups, performance of the left hemispace was better than that of the right hemispace and FS+ subjects performed better than FS- subjects. When the right hand was used, performance was correlated to MI scores only for FS- groups. Findings suggest that the correlation between right-sided neglect and proneness to schizotypy in normal right-handers is affected by FS.

Veering in women: inconsistency of forward and backward progression

In a large rectangular room, 13 blindfolded women attempted to walk in a straight line from one end of the room to a target centered at the other end of the room. On 12 trials, the women walked forward, and on 12 trials they walked backward. On half the trials under each of these conditions, they walked toward the north, and on the other half to the south. Performance errors were highly correlated for northward and southward progression, an indication of good reliability for this veering task. Veering during forward progression was not significantly related to veering during backward progression. Individual consistency in veering was demonstrated in several ways, and approximately half the participants veered in the same direction on nearly all trials. These results indicate that veering should be considered as an additional manifestation of lateral preferences in human motor behavior.

Turning bias in humans is influenced by phase of the menstrual cycle

Previous studies have provided evidence that humans demonstrate subtle, but measurable, turning biases when tested in the absence of environmental constraints. Preferences for leftward or rightward rotation have been repeatedly demonstrated in rodents and appear to be modulated to a significant degree by ovarian hormones, particularly estrogen. In the present study, we examined the turning biases of adult women at the midluteal and menstrual phases of the menstrual cycle, associated with high and low levels of estradiol and progesterone, respectively. Saliva samples were collected during each test session, and salivary concentrations of estradiol and progesterone were measured using radioimmunoassays. Overall, a rightward-turning bias was evident; however, a minority of the women displayed consistent leftward biases. Among right-turning subjects, turning biases were significantly weaker at the midluteal phase than at the menstrual phase. These results suggest that the mechanisms underlying human turning biases are subject to modulation by ovarian hormones.