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.     

Social support as a mediator in the relation between sensation seeking (need for stimulation) and psychological adjustment in older adults

This article investigates the potential role of social support as a mediator between sensation seeking (in the sense of a basal need for stimulation) and psychological adjustment in older adults. A sample of 325 individuals aged between 65 and 95 years were tested using questionnaires, which assess social support, sensation seeking, global self-worth, sense of coherence, and satisfaction with life. Path analyses provided support for a mediator model in which the relationship between sensation seeking and psychological adjustment was fully mediated by social support (the path coefficient between sensation seeking and psychosocial adjustment declines from β = .27 to β = .02, when adding an indirect path mediated by social support). Findings further suggest that this mediation effect was independent of sex and age. The study demonstrates the relevance of measuring sensation seeking as a personality trait in older adults.     

Mediational effects of sensation seeking on the age and financial risk-taking relationship

The current study examined the potential mediating role of sensation seeking in the well-established negative relationship between age and financial risk-taking. A total of 299 participants, aged 17–90 years, allocated hypothetical money into mutual funds that varied in risk and completed a sensation seeking measure. Hierarchical multiple regressions revealed that the amount of variability age accounted for in risk-taking (4.1%; β = −.22) was significantly reduced when sensation seeking was controlled for (0.8%; β = −.12). A Sobel test revealed that sensation seeking fully mediated the aforementioned relationship. Results suggest sensation seeking’s role as a mediator in more physiologically arousing risk-taking contexts (e.g., surfing). Discussion recommends investigating potential biologically and cognitively-rooted mediators and moderators of the age and risk-taking relationship.     

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.     

Lack of correlation between digit ratio (2D:4D) and Baron-Cohen’s “Reading the Mind in the Eyes” test, empathy, systemising, and autism-spectrum quotients in a general population sample

The second-to-fourth digit ratio (2D:4D) is sexually differentiated and is a likely biomarker for the organisational (permanent) effects of prenatal testosterone on the human brain. Recent research has highlighted a possible role of prenatal testosterone levels in both the etiology of autism-spectrum disorders and in sex and individual differences in cognitive styles of the normal mind (Baron-Cohen’s Extreme Male Brain Theory of Autism and Empathising/Systemising Theory). Importantly, autistic children present lower (hypermasculinised) 2D:4D than healthy controls. Based on these accounts, we investigated the relation of 2D:4D with Baron-Cohen’s measures of empathising (“Reading the Mind in the Eyes” test, RMET; Empathy Quotient, EQ), systemising (Systemising Quotient, SQ), and autistic-like traits (Autism-Spectrum Quotient, AQ) in the general population (N = 423 Austrian adults). Whereas sex differences into the expected direction and of expected size were obtained for all variables and internal scale consistencies tallied to retrievable reference values, 2D:4D was unrelated to RMET, EQ, SQ, and AQ scores. Candidate explanations for this lack of correlation might be possible developmental timing differences in the expression of 2D:4D and empathising/systemising, qualitative (as opposed to quantitative) functional differences between the normal and the autistic mind, or the suboptimal psychometric properties of the measures.     

Impulsivity and Sensation Seeking: Differing Associations with Psychological Well-Being

Sensation seeking and lack of inhibition are often discussed as risk factors for hazardous and maladaptive behavior, particularly during the transition into adulthood. However, some degree and types of novelty-seeking and exploration may also be adaptive and conducive to psychological well-being. The current study examines associations between sensation seeking, impulsivity, and well-being in a large US adult sample (n = 1399, mean age = 36.2 years, range: 18–78). As conceptualized by the UPPS-P model (Whiteside and Lynam, Personality and Individual Differences, 30(4), 669-689, 2001), sensation seeking (pursuit of stimulation) was distinguished from other forms of impulsivity (lack of inhibition) by having a positive association with psychological well-being, eudaimonic well-being, and mental health status. Those positive relations were stronger for younger adults compared to older adults. Negative urgency, lack of perseverance, lack of premeditation, and positive urgency all held either negative or null associations with well-being. Findings indicate that sensation seeking has positive associations with psychological and eudaimonic well-being, in contrast to other elements of impulsivity, and particularly among younger adults.

     

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.     

Childhood sexual abuse and impulsive personality traits: Mixed evidence for moderation by DRD4 genotype

This project examines associations between childhood sexual abuse (CSA) and two dimensions of impulsivity (sensation seeking and premeditation), and tests whether CSA-personality associations are moderated by the DRD4 exon III VNTR polymorphism. Sample 1 is from a longitudinal study of university students measured at 10 waves over ages 18–24 years (n = 500). Sample 2 is from a national sample of young adult sibling pairs, ages 18–24, from the National Longitudinal Study of Adolescent Health (n = 2559). In both samples, CSA was associated with elevated sensation seeking. In Sample 1, the association between CSA and sensation seeking was moderated by DRD4 genotype; this gene × environment interaction effect, however, was not replicated in Sample 2. Results suggest new avenues for research on CSA in the area of normal-range personality variation.     

Personality and risk-taking: common biosocial factors

The first part of this article describes a study of the relationships between personality and risk-taking in six areas: smoking, drinking, drugs, sex, driving, and gambling. The participants, 260 college students, were given self-report measures of risky behaviors in each of the six areas and the Zuckerman-Kuhlman five-factor personality questionnaire. Generalized risk-taking (across all six areas) was related to scales for impulsive sensation seeking, aggression, and sociability, but not to scales for neuroticism or activity. Gender differences on risk-taking were mediated by differences on impulsive sensation seeking. The second part discusses biological traits associated with both risk-taking and personality, particularly sensation seeking, such as the D4 dopamine receptor gene. the enzyme monoamine oxidase, and augmenting or reducing of the cortical evoked potential. Comparative studies show relationships between biological markers shared with other species and correlated behaviors similar to sensation seeking in humans. A biosocial model of the traits underlying risk-taking is presented.     

The effect of age and sensation seeking on pedestrian crossing safety in a virtual reality street

A wide range of individual, interpersonal and environmental factors influence the safety of pedestrians crossing the street, including human development (children take more risks than adolescents and adults) and sensation seeking (individuals higher in sensation seeking have greater risk). The interaction between those two variables has not been carefully studied, however. Does the effect of sensation seeking on pedestrian safety vary across human development as cognitive and other skills improve? This study investigated the primary effects of age and sensation seeking, plus their joint effects, on pedestrian crossing in a virtual reality environment. 209 children (10–13 years old), adolescents (14–18 years old) and young adults (20–24 years old) screened to be high and low level in sensation seeking participated. A 3 (age group: child vs adolescent vs young adult) × 2 (sensation seeking: high vs low) × 2 (traffic condition: easy vs harder crossing) mixed factorial design was conducted. Three pedestrian safety outcomes – start delay, missed opportunities and dangerous crossings – were considered. Results showed that when the traffic condition was easier to cross within, the start delay to enter traffic gaps was significantly shorter for children than for adolescents and young adults. There were no significant differences across age groups when the traffic condition was harder to cross within. Pedestrians also missed more opportunities to cross the road when the traffic condition was harder to cross within. Pedestrians low in sensation seeking missed more opportunities to cross than those high in sensation seeking. All age groups had more dangerous crossings during the harder crossing scenario than in the easier one, and adolescents had more dangerous crossings than young adults or children. Finally, the results of hierarchical regression models predicting dangerous crossings showed that traffic condition had a significant predictive effect on children's dangerous crossing behavior, and both high sensation seeking and harder traffic conditions predicted adolescents’ dangerous crossing behavior. No included variables significantly predicted adults' dangerous crossing behavior. We conclude that both age and sensation-seeking contribute to pedestrian safety. The effect of sensation seeking does not vary widely by age group, but its effect on adolescents was somewhat stronger than in the other age groups studied.     

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.     

Digit ratio (2D:4D) in twins: heritability estimates and evidence for a masculinized trait expression in women from opposite-sex pairs

The second-to-fourth digit ratio (2D:4D) is sexually dimorphic in humans, such that men on average have a lower 2D:4D than women. This somatic trait has been proposed as a biomarker for the organizational (permanent) effects of prenatal testosterone on the brain and behavior. Over the past few years, an accumulating research program has shown 2D:4D to be related to a multitude of sex-dependent, hormonally influenced psychological and behavioral traits. The present study investigated the 2D:4D ratio of 44 men and 70 women from 36 identical and 21 fraternal twin pairs. Both basic and advanced approaches for estimating heritability concordantly suggested that the trait is substantially heritable. The best-fitting structural equation model indicated that the contributions to individual differences in 2D:4D are 81% additively genetic, 19% nonshared environmental, and 0% shared environmental. Supplemental analyses showed that, consistent with a prediction from sex-hormone transfer theory, women from opposite-sex fraternal twin pairs had significantly lower (more male-typical) 2D:4D than women from same-sex fraternal twin pairs. Directions for research are discussed, such as investigating possible influences of the sex chromosomes on the expression of 2D:4D. Further family studies will be needed to test whether the transmission mode of 2D:4D is consistent with X-linked or Y-linked inheritance. The study of sex chromosome aberrations should indicate whether the presence of additional X or Y chromosomes is associated with 2D:4D levels.     

Sensation seeking and danger invulnerability: Paths to college student risk-taking

This study examines the roles of sensation seeking and invulnerability as predictors of health compromising behaviors in a multiethnic sample of 1690 emerging adult college students (mean age = 19.8, range 18–25 years) from nine US colleges and universities. Participants completed the Arnett Sensation Seeking Inventory and the Adolescent Invulnerability Scale; and reported how often they had participated in a set of health compromising risk behaviors (i.e., substance use, impaired driving, and sexual behaviors) in the 30 days prior to assessment. Sensation seeking and danger invulnerability scores were moderately correlated (r = .30). Findings from a series of multivariate Poisson regression analyses suggest that when considered simultaneously as predictors, sensation seeking appears to be a general risk factor associated with engagement in a variety of risk behaviors, whereas danger invulnerability is primarily a factor in those risk behaviors that are less common among peers (e.g., hard drug use, casual sex, and driving while intoxicated).     

Relationships of smiling and flirtation to aggression and 2D:4D, a prenatal androgen index

Smiling has been reported to be a signal of submission/lower status, or a sign of cooperation. In the present study, use of smiling and flirtation to "make people receptive to my ideas" was conceptualized as mild aggression, since it is mildly manipulative of the perception of others as to one's internal emotional status. For 91 participants (55 female, 36 male), use of smiling and flirtation to make others receptive to one's ideas were associated with relational aggression and a more male-typical (smaller) right 2D:4D finger length ratio. The only significant relationship in the male sample alone was the relationship between smiling and relational aggression. In the female sample alone, use of smiling and flirtation to "make people receptive to my ideas" was associated with a more male-typical 2D:4D finger length ratio pattern, and there was a trend for flirtation to be associated with greater physical aggression. Both 2D:4D and physical aggression have been associated with higher prenatal androgen level. It is concluded that deliberate smiling and flirtation are mild forms of relational aggression, and are related to prenatal androgenic activity in a manner similar to physical aggression. These findings are discussed in terms of the different evolutionary strategies of men and women to control their social environments.     

Widgets: A new set of parametrically defined 3D objects for use in haptic and visual categorization tasks

IntroductionMost research to date on human categorization ability has concentrated on the visual and auditory domains. However, a limited – but non-negligible – range of studies has also examined the categorization of familiar or unfamiliar (i.e., novel) objects in the haptic (i.e., tactile-kinesthetic) modality.ObjectiveIn this paper, we describe how we developed a new set of parametrically defined objects, called widgets, that can be used as 3D (or 2D) materials for haptic (or visual) categorization purposes.MethodWidgets are unfamiliar complex 3D shapes with an ovoid body and four types of elements attached to it (eyes, tail, crest, and legs). The stimulus set comprises 24 objects divided into four categories of six exemplars each (the files used for 3D printing are provided as Supplementary Material).ResultsWe also assessed and demonstrated the validity of our stimulus set by conducting two separate studies of haptic and visual categorization, involving participants of different ages: young adults (Study 1), and children and adolescents (Study 2). Results showed that humans can categorize our 3D complex shapes on the basis of both haptically and visually perceived similarities in shape attributes.ConclusionWidgets are very useful new experimental stimuli for categorization studies using 3D printing technology.     

Neural underpinnings of the relationships between sensation seeking and emotion regulation in adolescents

There is little neurological evidence linking sensation seeking and emotion regulation in adolescence, which is characterised as an emotionally fluctuant period. The present study examined the relationship between sensation seeking and emotion regulation in adolescents. Electroencephalograms were recorded from 22 high sensation-seeking adolescents (HSSs, M_age = 12.36) and 24 low sensation-seeking adolescents (LSSs, M_age = 12.84) during the reactivity and regulation-image task. Group differences in event-related brain potentials (ERPs) associated with the regulation of negative and neutral stimuli were analysed. The results showed that (a) the P2 of HSSs were larger than LSSs during emotion regulation; (b) in down-regulation conditions, the LPP in all time windows were smaller than no-regulation in LSSs. However, there was no significant difference in HSSs; (c) the LPP 300–600 and LPP 1000–1500 of down-regulation were smaller in LSSs than HSSs; (d) for LPP 600–1000, HSSs induced larger LPP than LSSs in the negative down-regulation and negative no-regulation conditions. The results provide neurological evidence that higher sensation seeking is related to the high reactivity to emotional stimuli and poor cognitive control during the regulation of emotions.     

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.     

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.     

An Assessment of the Psychometric Properties of the Brief Sensation Seeking Scale for Children

Sensation seeking is a trait that predicts a wide range of real-life risk behavior, such as substance abuse and gambling problems. Sensation seeking is often assessed with the Sensation Seeking Scale. Several adaptations of this questionnaire have been made, for example, to abbreviate it and to make it suitable for children. However, studies on sensation seeking in children are scarce. The aim of this study was to investigate sensation seeking in children (N = 158, M age = 11.4 years). The Brief Sensation Seeking Scale for Children (BSSS–C) was translated into Dutch and psychometric properties were examined. Internal consistency was high, and the factor structure showed close resemblance with previous research. Test–retest and split-half reliabilities were acceptable, as was convergent validity with self-reported symptoms of psychopathology (attention problems and aggressive behavior). Construct validity was adequate, with more sensation seeking in boys than in girls. No effects of age were found. To sum up, sensation seeking can be measured in children in a valid and reliable way. The correlation of sensation seeking with high-risk behaviors emphasizes the importance of assessment early in development.     

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.