Digit ratio (2D:4D) and sex-role orientation: Further evidence and meta-analysis

Three new studies (N = 132, 623, 1112) did not yield hypothesized associations between digit ratio (2D:4D), an assumed negative correlate of prenatal testosterone, and psychometrically measured sex-role orientation (positive association with femininity, negative ones with masculinity and masculinity-femininity difference scores) among heterosexuals of either sex. Meta-analysis of the pertinent literature (N = 6311, 28 studies from 10 countries, 46% unpublished) showed only men’s (but not women’s) left-hand (but not right-hand) 2D:4D reliably related as expected (positively) to femininity. This effect was tiny (0.14% attributable variance) and possibly non-robust (crucially dependent on one large study included). Hence, the cumulative evidence does not support systematic, robust, noteworthy within-sex correlations between 2D:4D and the masculinity/femininity personality dimensions.     

2D:4D in men is related to aggressive dominance but not to sociable dominance

It has been shown that a smaller ratio between the length of the second and fourth digit (2D:4D) is an indicator of the exposure to prenatal testosterone (T). This study measured the 2D:4D of men and assessed dominance as a personality trait to investigate indirectly if the exposure to prenatal T is related to a dominant personality later in life. Results showed that men had a more aggressive dominant personality when having a more masculine (lower) 2D:4D, while there was no relationship between sociable dominance and 2D:4D. Findings from this study indicate that it is important to distinguish different forms of dominance since other studies failed to find relationships between dominance and 2D:4D.     

The effect of prenatal androgen exposure on the development of neural reactivity systems: A study of the HEXACO Personality Inventory

The ratio of the lengths of the second and fourth digits of hands (2D:4D) seems to vary as a function of systematic differences in prenatal androgen exposure (Hönekopp & Watson, 2010). The 2D:4D ratio has been shown to be related to a variety of personality attributes. This study predicted that 2D:4D would covary with scores on the emotionality dimension of the six-facet HEXACO personality assessment, due to emotionality’s relationship with neural reactivity systems controlled by the amygdala (Hines, Allen, & Gorski, 1992), but that 2D:4D would relate to no other facet. Consistent with hypotheses, data showed that men had smaller ratios than women on both the right, t(405) = 2.84, p < .05, d = .28, and left hands, t(405) = 4.51, p < .05, d = .45, and the relationship between 2D:4D and emotionality was outside of sampling error of zero, r = .18, p < .001. Additionally, 2D:4D was unrelated to the remaining HEXACO facets. Findings suggest that prenatal testosterone exposure has an organizing effect on personality traits.     

Meta-analysis of the relationship between digit-ratio 2D:4D and aggression

Males tend to be more aggressive than females and the organizational effects of prenatal testosterone (T) appear to contribute to this sex difference. Low second-to-fourth digit ratio (2D:4D) is thought to be a marker of high prenatal testosterone. For this reason, a number of studies have used 2D:4D to investigate a potential effect of prenatal T upon aggression in later life. Here we meta-analyse these studies to determine the true size of the relationship between 2D:4D and aggression. We find no evidence of 2D:4D better predicting aggression at different levels of risk nor do we find evidence for a relationship between 2D:4D and aggression in females. Regarding males we find some evidence of a small, negative relationship between 2D:4D and aggression (r ≈ −.06) and no indication that either hand would predict aggression better than the other. We contrast these findings with results regarding levels of aggression in females with elevated prenatal T levels due to Congenital Adrenal Hyperplasia and we discuss implications for 2D:4D research.     

Digit ratio (2D:4D) and Cattell's personality traits

The ratio between second and fourth finger (2D:4D) is sexually dimorphic; it is lower in men than in women. Studies using broad personality domains yielded correlations of 2D:4D with neuroticism, extraversion or agreeableness, but the obtained results have been inconsistent. We correlated 2D:4D of 184 women and 101 men with their scores in Cattell's 16 Personality Factor (16PF) Questionnaire. We found women with a higher (more ‘feminine’) right hand 2D:4D to score lower in emotional stability and social boldness and higher in privateness. Mediator analysis showed emotional stability to be probably primarily correlated with 2D:4D and to act as a mediator between 2D:4D and social boldness. Privateness appears to be mediated by an even more complex path. We discuss the usefulness of primary‐level personality questionnaires and mediator analyses in the investigation of psycho‐morphological associations. Copyright © 2007 John Wiley & Sons, Ltd.     

The 2nd to 4th digit ratio (2D:4D) and eating disorder diagnosis in women

Eating disorders are more common in females than in males and are believed to be caused, in part, by biological and hormonal factors. Digit ratio or 2D:4D (the ratio of the 2nd to the 4th digit) is considered to be a proxy for prenatal testosterone (PT) and prenatal oestrogen (PE) exposure. However, how 2D:4D may be related to type of eating pathology is unknown. The relationship between 2D:4D and eating disorder diagnosis was investigated in recovered and currently eating disordered (n = 31) and control (n = 99) women. Mean 2D:4D ratio was significantly lower (indicating higher levels of PT and lower levels of PE) in anorexic (AN) compared to bulimic (BN) women, with controls intermediary. In eating disordered women, 2D:4D was positively and significantly related to current weight, lowest weight and current BMI, with strongest associations for right 2D:4D. Among women, low 2D:4D is related to AN and high 2D:4D to BN, suggesting a differential causal influence of prenatal sex hormones on later eating pathology.     

On the relationship between explicit and implicit self-concept of extraversion and neuroticism

Indirect methods such as the implicit association test (IAT) could complement traditional self-report questionnaires of personality traits. However, it is unclear whether IAT scores and self-report scores of nominally the same personality trait measure the same construct or overlapping but distinct constructs. To investigate how IAT and self-report personality scores relate to each other, we conducted a web-based data collection where participants completed self-report personality questionnaires (n = 432) and IATs for extraversion (n = 393) and neuroticism (n = 385). We found that extraversion self-report and IAT scores were more strongly correlated with each other than corresponding neuroticism scores. Overall, our findings suggest that although extraversion and neuroticism self-report and implicit measures are related, they do measure distinct constructs.     

Relationships between digit ratio 2D:4D and self-reported aggression and risk taking in an online study

2D:4D, the length ratio of the second to the fourth digit, is a putative measure of prenatal testosterone, which may have effects on aggression and risk taking. Participants in a German online study (>1000 females, >1200 males) submitted their self-measured digit lengths and self-report measures on verbal and physical aggression and risk taking. For males, left-hand 2D:4D and verbal aggression correlated significantly (r = −.10, after correction for age and reduced reliability in self-measured 2D:4D), with other relationships being similar but non-significant. For females, no relationships between aggression and 2D:4D were found. Risk taking and right-hand 2D:4D correlated significantly in women (r = −.10, after correction for age and reduced reliability in self-measured 2D:4D); similar, but statistically non-significant, relationships were found in men. The result corroborates an emerging view that 2D:4D is negatively related to aggression in males and that 2D:4D is negatively related to risk taking. This tentatively points to effects of prenatal testosterone on these characteristics.     

Domain Specific Relationships of 2D:4D Digit Ratio in Risk Perception and Risk Behavior

The 2D:4D digit ratio (henceforth, 2D:4D) is accepted as a marker of prenatal testosterone, demonstrating gender differences. The present study reveals that 2D:4D shows not only gender differences but also individual differences in personality and risk-taking behavior. We measured individual participants’ 2D:4D, structural personality, and risk-taking attitude scores. The result of the current study replicates the gender difference in 2D:4D in previous researches. However, we found different aspects of the correlations among 2D:4D, personality, and risk-taking attitude. Path analyses indicated that 2D:4D passes through personality factors before reaching the risk-taking attitude, particularly in the financial domain activities of investing and gambling. Also we observed a specific relationship between right-hand 2D:4D and emotionality and between left-hand 2D:4D and agreeableness. Finally, we suggest multiple path models of 2D:4D and personality in risk taking depending on the domain.     

Bulimia nervosa: a descriptive and therapeutic study

This study examined a sample of 24 Ss who met strict criteria for a diagnosis of bulimia nervosa. Assessments were made on: (1) demographic characteristics, (2) eating attitudes and behaviour and (3) personality measures. The effectiveness of two types of therapeutic intervention (cognitive-behavioural group therapy vs cognitive-behavioural group therapy plus specific behavioural instruction) was examined in a baseline, therapy intervention, follow-up design.The group was characterized prior to therapy by high N, Depression and Anxiety and low Self-esteem scores compared with control group data. Following therapy, Depression and Anxiety scores were significantly lower and Self-esteem scores higher, whereas N scores remained high. Binge-purging frequencies were significantly reduced in some of the Ss but the reduction could not unequivocally be attributed to the therapeutic interventions. The pattern of results suggested that bulimia nervosa (defined by a binge-purging pattern in association with high neuroticism) should be distinguished from bulimia (defined by a binge pattern not related to purging or high neuroticism) and that DSM-III should be revised to reflect this distinction. A theory is advanced to account for the rapid association of binging and purging in Ss high in neuroticism but not in Ss low in neuroticism.     

Investigating digit ratio (2D:4D) in a highly male‐dominated occupation: The case of firefighters

Voracek, M., Pum, U. & Dressler, S. G. (2009). Investigating digit ratio (2D:4D) in a highly male‐dominated occupation: The case of firefighters. Scandinavian Journal of Psychology, 51, 146–156. Second‐to‐fourth digit ratio (2D:4D), a widely studied putative marker for masculinization through prenatal androgen exposure, is lower (more masculinized) in athletes than in general population controls, and athletes with lower 2D:4D have higher sporting success. Occupations differ markedly in perceived masculinity and actual maleness (sex ratios), but these givens have not yet been picked up and utilized in 2D:4D research. Accordingly, this study extended existing accounts on 2D:4D in athletes to a novel approach: 2D:4D and possible relationships to a variety of candidate variables (demographic, fertility‐related, psychological, and other) were investigated in firefighters, a highly male‐dominated occupation. Contrary to expectation, 2D:4D in firefighters (N = 134) was not lower than in local male population controls. Lower 2D:4D corresponded to lower service ranks. Replicating previous findings either unequivocally or partly, lower 2D:4D was associated with larger family size, later sibling position, left‐handedness, and higher scores in the disinhibition component of sensation seeking. Not replicating prior evidence, 2D:4D was unrelated to body‐mass index, offspring sex ratio, and sporting performance level. Novel findings included low 2D:4D in those with low relationship satisfaction and in cigarette smokers, especially among heavy smokers. Absolute finger length, a positive correlate of pubertal‐adolescent androgen levels, was also considered. This marker showed negative associations with relationship consensus and satisfaction and positive ones with perceived quality of relationship alternatives and the experience seeking component of sensation seeking. The merits of this additional marker, relative to 2D:4D, for supplementing studies of possible sex‐hormonal effects on personality and directions for future inquiry along these lines are discussed.     

Digit ratio (2D:4D), academic performance in computer science and computer-related anxiety

Being able to use information communication technology (ICT) effectively has become an essential element of participation within an increasingly digital culture. However, there are differences in participation within this digital culture. Prenatal testosterone exposure is thought to influence the development of numeric capabilities and relate to levels of anxiety, both of which contribute towards engagement with ICT. This study examined whether an index of prenatal exposure to testosterone, digit ratio (2D:4D), is related to successful involvement within a computer-technology context - performance in a Java programming course. Three studies (N = 73,75,65) identified a consistent negative correlation between 2D:4D digit ratio and attainment (r ≈ −0.2). A fourth study (N = 119) found that 2D:4D digit ratio positively correlated with two indices of computer-related anxieties, as well as anxiety sensitivity (r = 0.32/0.51). These results suggest that males and females who have been exposed to higher levels of testosterone within the womb perform better upon academic assessments of Java-related programming ability within computer science education, and have lower levels of computer-related anxieties outside computer science education. Thus, the 2D:4D index of prenatal testosterone exposure correlated with the two factors that directly impact upon ICT engagement, which is increasingly essential to effectively participate within educational and occupational environments.     

Type D personality and the development of PTSD symptoms: a prospective study

Psychological trauma and prolonged stress may cause mental disorders such as posttraumatic stress disorder (PTSD). Pretrauma personality is an important determinant of posttraumatic adjustment. Specifically, trait neuroticism has been identified as a risk factor for PTSD. Additionally, the combination of high negative affectivity or neuroticism with marked social inhibition or introversion, also called Type D personality (Denollet, 2000), may compose a risk factor for PTSD. There is no research available that examined pretrauma Type D personality in relation to PTSD. The present study examined the predictive validity of the Type D personality construct in a sample of Dutch soldiers. Data were collected prior to and 6 months after military deployment to Afghanistan. Separate multiple regression analyses were performed to examine the predictive validity of Type D personality. First, Type D personality was defined as the interaction between negative affect and social inhibition (Na × Si). In a second analysis, Type D was defined following cutoff criteria recommended by Denollet (2000). Results showed that negative affectivity was a significant predictor of PTSD symptoms. Social inhibition and the interaction Na × Si did not add to the amount of explained variance in postdeployment PTSD scores over the effects of childhood abuse, negative affectivity, and prior psychological symptoms. A second analysis showed that Type D personality (dichotomous) did not add to the amount of explained variance in postdeployment PTSD scores over the effects of childhood abuse, and prior psychological symptoms. Therefore, Type D personality appears to be of limited value to explain development of combat-related PTSD symptoms.     

The distressed (Type D) and Five-Factor Models of personality in young,healthy adults and their association with emotional inhibition and distress

The distressed (Type D) personality (the combination of negative affectivity and social inhibition traits) has been associated with adverse health outcomes. This study investigated the validity of the Type D construct against the Five-Factor Model (FFM) of personality, and its association with emotional control and distress. In total 498 university students (mean age 28.9 ± 8.4 years) completed the Type D scale (DS14), and measurements for the FFM of personality, emotional control, anxiety, depression and stress. The construct validity of the Icelandic DS14 was confirmed. The Type D components negative affectivity and social inhibition were strongly associated with neuroticism and extraversion of the FFM (r = 0.82 and r = −0.67, respectively). Negative affectivity also correlated with rehearsal/rumination (r = 0.58) and social inhibition with emotional inhibition (r = 0.54), indicative of emotional control. Type D personality (40% of sample) was associated with higher levels of anxiety, depression and stress. The Type D personality components were associated with the FFM of personality, emotional control and emotional distress. Importantly, social and emotional inhibition were closely related, providing novel information about the presence of emotional inhibition within the social inhibition trait.     

Construct, concurrent and discriminant validity of Type D personality in the general population: associations with anxiety, depression, stress and cardiac output

The Type D personality, identified by high negative affectivity paired with high social inhibition, has been associated with a number of health-related outcomes in (mainly) cardiac populations. However, despite its prevalence in the health-related literature, how this personality construct fits within existing personality theory has not been directly tested. Using a sample of 134 healthy university students, this study examined the Type D personality in terms of two well-established personality traits; introversion and neuroticism. Construct, concurrent and discriminant validity of this personality type was established through examination of the associations between the Type D personality and psychometrically assessed anxiety, depression and stress, as well as measurement of resting cardiovascular function. Results showed that while the Type D personality was easily represented using alternative measures of both introversion and neuroticism, associations with anxiety, depression and stress were mainly accounted for by neuroticism. Conversely, however, associations with resting cardiac output were attributable to the negative affectivity-social inhibition synergy, explicit within the Type D construct. Consequently, both the construct and concurrent validity of this personality type were confirmed, with discriminant validity evident on examination of physiological indices of well-being.     

Personality and accident liability: are extraversion, neuroticism and psychoticism related to traffic and occupational fatalities?

The aim of the present study was to investigate the relationship between extraversion, neuroticism and psychoticism, and road traffic fatalities in a data set of 34 nations. In addition to traffic fatalities per 100,000 vehicles, work-related fatalities were included in the study. Results showed that extraversion had a positive relation to the number of traffic fatalities whereas neuroticism correlated negatively with road fatalities. Occupational fatalities were strongly related to deaths on the roads but not to personality dimensions. Countries with high extraversion scores had more traffic fatalities than countries with moderate or low extraversion scores. The need for well-designed studies investigating the link between personality factors and traffic accident liability via driver behaviour was expressed.     

Testosterone and domain-specific risk: Digit ratios (2D:4D and rel2) as predictors of recreational, financial, and social risk-taking behaviors

Prenatal testosterone has important effects on brain organization and future behavior. The second-to-fourth digit length ratio (2D:4D), a proxy of prenatal testosterone exposure, has been linked to a wide variety of sexually differentiated dispositions and behaviors. We examine the relationship between digit length ratios (2D:4D and rel2, the length of the second finger relative to the sum of the lengths of all four fingers) and risk-taking behaviors across five domains: financial, social, recreational, ethical, and health. In a sub-sample of male Caucasians (ethnically homogeneous), lower rel2 was predictive of greater financial, social, and recreational risk-taking, whereas lower 2D:4D was predictive of greater risk-taking in two domains (social and recreational). In the full male sub-sample (ethnically heterogeneous), the only significant correlation was a negative association between 2D:4D and financial risk. A composite measure of risk-taking across all five domains revealed that both rel2 and 2D:4D were negatively correlated with overall risk-taking in both male sub-samples. No significant correlations were found in the female sub-samples. Finally, men were more risk-seeking than women across all five contexts.     

On the relationship between personality and time estimation

The influence of basic dimensions of personality, such as extraversion, neuroticism, and psychoticism, on estimation of time still appears to be unclear. Therefore, in the present study the relationship between Eysenck's basic dimensions of personality and time estimation was investigated in 34 male Ss. After filling in the short version of a German adaptation of the Eysenck Personality Questionnaire-Revised, Ss were required to reproduce target durations ranging from 5 to 40 sec. As a measure of performance, reproduction ratio scores, representing directional errors, and absolute error scores were computed. Correlational analyses revealed no indication of a linear relationship between neuroticism and time estimation. However, there was a tendency for extraverts to overestimate time and to make less accurate time judgments relative to introverts. Furthermore, Ss with higher psychoticism scores were less prone to overestimation of time intervals and showed better accuracy of temporal reproductions than Ss with lower psychoticism scores.     

Neuroticism and extraversion are associated with amygdala resting-state functional connectivity

The personality traits neuroticism and extraversion are differentially related to socioemotional functioning and susceptibility to affective disorders. However, the neurobiology underlying this differential relationship is still poorly understood. This discrepancy could perhaps best be studied by adopting a brain connectivity approach. Whereas the amygdala has repeatedly been linked to neuroticism and extraversion, no study has yet focused on the intrinsic functional architecture of amygdala-centered networks in relation to both traits. To this end, seed-based correlation analysis was employed to reveal amygdala resting-state functional connectivity (RSFC) and its associations with neuroticism and extraversion in 50 healthy participants. Higher neuroticism scores were associated with increased amygdala RSFC with the precuneus, and decreased amygdala RSFC with the temporal poles, insula, and superior temporal gyrus (p < .05, cluster corrected). Conversely, higher extraversion scores were associated with increased amygdala RSFC with the putamen, temporal pole, insula, and several regions of the occipital cortex (p < .05, cluster corrected). The shifts in amygdala RSFC associated with neuroticism may relate to the less-adaptive perception and processing of self-relevant and socioemotional information that is frequently seen in neurotic individuals, whereas the amygdala RSFC pattern associated with extraversion may relate to the heightened reward sensitivity and enhanced socioemotional functioning in extraverts. We hypothesize that the variability in amygdala RSFC observed in the present study could potentially link neuroticism and extraversion to the neurobiology underlying increased susceptibility or resilience to affective disorders.     

Extraversion,neuroticism, psychoticism and self-reported delinquency: Evidence from eight separate samples

Eight separate samples of high school and university students (Total N = 410) in Britain and Canada were used to test predictions from Eysenck's theory that delinquents should be high scorers on scales of extraversion, neuroticism, and psychoticism. Self-report paper- and pencil-questionnaire measures of both personality and delinquency were administered under conditions that ensured anonymity. The evidence showed clear support for a relationship between high delinquency scores and high scores on both extraversion and psychoticism. These relationships held up across diverse samples and different ways of analyzing the data. No support was found for a relationship between delinquency scores and the dimension of neuroticism.