Picture recall skills correlate with 2D:4D ratio in women but not men

Gender Differences in Large-Scale and Small-Scale Spatial Ability: A Systematic Review Based on Behavioral and Neuroimaging Research

Background: As we human beings are living in a multidimensional space all the time. Therefore, spatial ability is vital for the survival and development of individuals. However, males and females show gender differences in this ability. So, are these gender differences influenced by the scale type of spatial ability? It's not well specified. Therefore, to tackle this issue, we conducted the current research from the behavioral and neural level. Methods: Study 1 used the general meta-analysis method to explore whether individuals display the same gender differences in large- and small-scale spatial ability. Study 2 used the method of Activation Likelihood Estimation to identify the commonalities and distinctions of the brain activity between males and females on large- and small-scale spatial ability. Results: Study 1 showed that in behavior performance, males outperformed females in both large-scale and small-scale spatial ability, but the effect size of the gender difference in large-scale spatial ability is significantly greater than that in small-scale spatial ability. In addition, Study 2 showed that in terms of neural activity, males and females exhibited both similarities and differences no matter in large-scale or small-scale spatial ability. Especially, the contrast analysis between females and males demonstrated a stronger activation in the brain regions of bilateral lentiform nucleus and bilateral parahippocampal gyrus in large-scale spatial ability, and correspondence in right sub-gyral, right precuneus, and left middle frontal gyrus in small-scale spatial ability. Conclusions: The results indicated that the reason why females performed not so well in large-scale spatial ability was that they were more susceptible to emotions and their parahippocampal gyrus worked less efficiently than males; females performed not so well in small-scale spatial ability because they mostly adopted the egocentric strategy and their sub-gyral also worked less efficiently than males. The two different reasons have made for gender differences in favor of males in terms of spatial ability and such gender differences have different manifestations in large-scale and small-scale spatial ability. Possible implications of the results for understanding the issue of gender differences in spatial ability are discussed.

Second-to-fourth digit length ratio is associated with negative and affective symptoms in schizophrenia patients

BACKGROUND

Higher levels of circulating oestrogens in women and testosterone in men have been shown to have a protective effect against the clinical manifestations of schizophrenia, mostly with respect to negative symptomatology. Certain studies suggest that they also have a protective effect against the neuropsychological impairment observed in the disease. We investigated whether greater prenatal exposure to estrogens in women and to testosterone in men, reflected by the 2D:4D ratio, was similarly associated with decreased negative symptomatology and improved neuropsychological functioning in patients.

METHOD

51 schizophrenia patients and 50 healthy participants were administered a neuropsychological battery. The 2D:4D ratio was measured in all participants. Positive, negative, and affective symptoms were assessed in patients. Regression analyses were conducted separately in male and female subgroups.

RESULTS

No associations with positive symptoms were revealed. In male patients, the 2D:4D ratio was positively associated with avolition and inversely associated with anxiety. In female patients, it was inversely associated with alogia, and tended to be positively associated with depression. No association between higher prenatal concentration of the relevant sex hormone and improved neuropsychological performance emerged in patients.

CONCLUSIONS

Higher concentrations of prenatal testosterone in male patients, and prenatal oestrogens in female patients, are associated with a decrement in certain aspects of negative symptomatology. In addition, prenatal sex hormone concentration seems to be associated with predisposition to anxiety in male patients, and to depression in female patients.

Can exposure to prenatal sex hormones (2D:4D) predict cognitive reflection?

The Cognitive Reflection Test (CRT) is a test introduced by Frederick (2005). The task is designed to measure the tendency to override an intuitive response that is incorrect and to engage in further reflection that leads to the correct response. The consistent sex differences in CRT performance may suggest a role for prenatal sex hormones. A now widely studied putative marker for relative prenatal testosterone is the second-to-fourth digit ratio (2D:4D). This paper tests to what extent 2D:4D, as a proxy for the prenatal ratio of testosterone/estrogens, can predict CRT scores in a sample of 623 students. After controlling for sex, we observe that a lower 2D:4D (reflecting a relative higher exposure to testosterone) is significantly associated with a higher number of correct answers. The result holds for both hands' 2D:4Ds. In addition, the effect appears to be stronger for females than for males. We also control for patience and math proficiency, which are significantly related to performance in the CRT. But the effect of 2D:4D on performance in CRT is not reduced with these controls, implying that these variables are not mediating the relationship between digit ratio and CRT.

Sex and modulatory menstrual cycle effects on sleep related memory consolidation

The benefit of sleep in general for memory consolidation is well known. The relevance of sleep characteristics and the influence of hormones are not well studied. We explored the effects of a nap on memory consolidation of motor (finger-tapping-task) and verbal (associated-word-pairs) tasks in following settings: A: young, healthy males and females during early-follicular phase (n=40) and B: females during mid-luteal and early-follicular phase in the menstrual cycle (n=15). We found a sex and in women a menstrual cycle effect on memory performance following a nap. Men performed significantly better after a nap and women did so only in the mid-luteal phase of their menstrual cycle. Only the men and the women in their mid-luteal phase experienced a significant increase in spindle activity after learning. Furthermore, in women estrogen correlated significantly with the offline change in declarative learning and progesterone with motor learning. The ratio of the 2nd and 4th digit, which has been associated to fetal sex hormones and cognitive sex differences, significantly predicted the average performance of the female subjects in the learning tasks. Our results demonstrate that sleep-related memory consolidation has a higher complexity and more influencing factors than previously assumed. There is a sex and menstrual cycle effect, which seems to be mediated by female hormones and sleep spindles. Further, contrary to previous reports, consolidation of a simple motor task can be induced by a 45 min NREM sleep nap, thus not dependent on REM sleep.

Organizing effects of testosterone and economic behavior: not just risk taking

Recent literature emphasizes the role that testosterone, as well as markers indicating early exposure to T and its organizing effect on the brain (such as the ratio of second to fourth finger, ), have on performance in financial markets. These results may suggest that the main effect of T, either circulating or in fetal exposure, on economic behavior occurs through the increased willingness to take risks. However, these findings indicate that traders with a low digit ratio are not only more profitable, but more able to survive in the long run, thus the effect might consist of more than just lower risk aversion. In addition, recent literature suggests a positive correlation between abstract reasoning ability and higher willingness to take risks. To test the two hypotheses of testosterone on performance in financial activities (effect on risk attitude versus a complex effect involving risk attitude and reasoning ability), we gather data on the three variables in a sample of 188 ethnically homogeneous college students (Caucasians). We measure a digit ratio, abstract reasoning ability with the Raven Progressive Matrices task, and risk attitude with choice among lotteries. Low digit ratio in men is associated with higher risk taking and higher scores in abstract reasoning ability when a combined measure of risk aversion over different tasks is used. This explains both the higher performance and higher survival rate observed in traders, as well as the observed correlation between abstract reasoning ability and risk taking. We also analyze how much of the total effect of digit ratio on risk attitude is direct, and how much is mediated. Mediation analysis shows that a substantial part of the effect of T on attitude to risk is mediated by abstract reasoning ability.

Scientometric analysis and bibliography of digit ratio (2D:4D) research, 1998-2008

A scientometric analysis of modern research on the second-to-fourth digit ratio (2D:4D), a widely studied putative marker for prenatal androgen action, is presented. In early 2009, this literature totalled more than 300 publications and, since its initiation in 1998, has grown at a rate slightly faster than linear. Key findings included evidence of publication bias and citation bias, incomplete coverage and outdatedness of existing reviews, and a dearth of meta-analyses in this field. 2D:4D research clusters noticeably in terms of researchers, institutions, countries, and journals involved. Although 2D:4D is an anthropometric trait, most of the research has been conducted at psychology departments, not anthropology departments. However, 2D:4D research has not been predominantly published in core and specialized journals of psychology, but rather in more broadly scoped journals of the behavioral sciences, biomedical social sciences, and neurosciences. Total citation numbers of 2D:4D papers for the most part were not larger than their citation counts within 2D:4D research, indicating that until now, only a few 2D:4D studies have attained broader interest outside this specific field. Comparative citation analyses show that 2D:4D research presently is commensurate in size and importance to evolutionary psychological jealousy research, but has grown faster than the latter field. In contrast, it is much smaller and has spread more slowly than research about the Implicit Association Test Fifteen conjectures about anticipated trends in 2D:4D research are outlined, appendixed by a first-time bibliography of the entirety of the published 2D:4D literature.

Spatial ability and prenatal androgens: meta-analyses of congenital adrenal hyperplasia and digit ratio (2D:4D) studies

Hormonal manipulations indicate that early androgens organize sex differences in spatial ability in laboratory rats. In humans, spatial ability is also sexually dimorphic, and information about the effects of prenatal androgens on spatial ability can be obtained from studies of congenital adrenal hyperplasia (CAH) and the ratio of the second and fourth finger lengths (2D:4D). CAH is characterized by prenatal overproduction of adrenal androgens and several lines of evidence suggest that 2D:4D reflects prenatal androgen exposure. Some studies have found that these proxy measures of prenatal androgens predict spatial ability, others have found no significant relationship, and yet others have obtained results in the opposite direction. In light of these mixed findings, we conducted meta-analyses of published literature and unpublished results to determine if, across studies, either of these indicators of prenatal androgens predicts performance on spatial tasks that show a male advantage. In addition, we applied a trim and fill analysis to the data in search of asymmetry that might be an indication of publication bias. Results indicated that females with CAH perform better on these spatial tasks, and CAH males perform worse, than do controls. Little or no relationship exists between 2D:4D and spatial ability. Implications for possible hormonal contributions and the developmental timing of sex differences in spatial cognition are discussed.

Blocks and bodies: sex differences in a novel version of the Mental Rotations Test

A novel version of the Mental Rotations Test (MRT) that alternated the standard block figures with three-dimensional human figures was administered to 99 men and 129 women. Women and men differed predictably in their retrospective reports of childhood play and digit ratios, a putative measure of prenatal androgen action. Compared to the block figure items, human figure items on the modified MRT were associated with an improvement in performance in both sexes. However, consistent with the study hypothesis, the enhancing effect of the human figure condition on performance as measured by conventional scores was smaller in men compared to women and not at all evident in men when performance was measured by ratio scores. A closer inspection of the human figures effects on test scores showed performance in women improved for both male and female figure items. In contrast, relative to scores on block figure items, performance in men improved when stimuli were male figures but did not improve when stimuli were female figures. These results add to the evidence that the magnitude of sex differences in scores on the MRT may vary according to the test content and item properties. The findings suggest that online measures of cognitive processing in response to different classes of test stimuli (e.g., animate vs. inanimate objects, self-relevant vs. neutral stimuli) may prove useful in research aimed at understanding the hormonal and social factors contributing to the sex difference in performance on the MRT.

Androgens and eye movements in women and men during a test of mental rotation ability

Eye movements were monitored in 16 women and 20 men during completion of a standard diagram-based test of mental rotation ability to provide measures of cognitive function not requiring conscious, decisional processes. Overall, women and men allocated visual attention during task performance in very similar, systematic ways. However, consistent with previous suggestions that sex differences in attentional processes during completion of the mental rotation task may exist, eye movements in men compared to women indicated greater discrimination and longer processing of correct alternatives during task performance. Other findings suggested that androgens may enhance cognitive processes that are recruited differentially by women and men as a function of the task. Specifically, smaller (i.e., more masculine) digit ratios were associated with men's shorter fixations on distracters, suggesting that perinatal androgen action may influence brain systems that facilitate the identification of relevant task stimuli. In women, higher circulating testosterone levels appeared to contribute to more general processes engaged during task performance, for example higher levels of visual persistence. It is possible that variability in the relative contribution of such hormone sensitive cognitive processes to accuracy scores as a function of different sample characteristics or assessment methods may partially account for the inconsistent findings of previous research on hormonal factors in mental rotation ability.

Digit Ratio (2D:4D) and Lateralization for Basic Numerical Quantification

Abstract. The ratio between the second and fourth fingers (2D:4D) is supposed to serve as a putative indicator of prenatal testosterone (PT). Significant associations between 2D:4D, children's basic numerical ability, and the Spatial Numerical Associations of Response Codes (SNARC) effect have recently been reported. The present study explored potential relationships between 2D:4D and the basic numerical ability of subitizing (the rapid enumeration of small quantities) in 80 right-handed adult volunteers. Participants completed a short battery of computerized subitizing and color recognition control tasks with both left and right hands, independently (order counterbalanced). Findings revealed a significant interaction between sex and 2D:4D on reaction time differences for right vs. left hand responses to the subitizing task. While 2D:4D in women showed a significant negative association with a right-hand advantage for the task, a nonsignificant trend in the opposite direction was observed for men. Results are discussed with respect to the possible effect of PT on sex differences in lateralization for basic quantification.

Digit ratio (2D:4D) and the spatial representation of magnitude

Digit ratio (as a putative indicator of prenatal androgen exposure) is related to a range of sexually dimorphic abilities, including spatial skills and mathematical ability. This study examined a phenomenon known as the SNARC effect (Spatial Numerical Association of Response Codes), which is taken as evidence of a mental representation of magnitude along a left-right-oriented number line, with low magnitudes associated with the left side of space, and high numbers with the right side of space. Participants made a parity judgement of numbers with responses made with a left key to odd numbers and a right key to even numbers. This was reversed for a second block of trials. Response times to numbers one to nine with both the right and left hand were calculated, and regression analyses conducted to analyse whether lower magnitudes were responded to faster with the left hand and higher magnitudes with the right hand. Participants with lower (more masculine) digit ratios on the right hand showed a stronger SNARC effect compared to participants with high digit ratios. This pattern of results was also found when the analyses were conducted separately for men and women. Results from left hand digit ratios indicated that only low digit ratio females showed a significant SNARC effect. These findings add to a growing literature on the relationship between digit ratio and cognitive abilities; in this case, simple cognitive representations that are accessed automatically rather than complex skills such as mental rotation or "mathematics" where a variety of solution strategies may be utilised.