Dark Triad Personality Traits, Second-to-Forth Digit Ratio (2D:4D) and Circulating Testosterone and Cortisol Levels

INTRODUCTION

Dark Triad (DT) personality traits (psychopathy, Machiavellianism, and narcissism) show sex differences and associations with hormones. Understanding aetiology may assist in mitigating the harm of these potentially adverse characteristics. Low second-to-fourth digit ratio (2D:4D) is hypothesised to be a marker of high prenatal testosterone exposure and may provide important information about organisational hormones. The aim of the present study was to measure Dark Triad and Big 5 personality traits in relation to digit ratio, salivary testosterone, and cortisol.

METHODS

A non-clinical sample (N=268; 49.25% Female, age M25.20 ± 8.77yrs) completed the Short Dark Triad and International Personality Inventory Pool - Mini. Afternoon saliva was analysed for testosterone and cortisol, and 2D:4D finger ratios were measured.

RESULTS

Males scored higher on DT traits than females. Females scored higher on Big 5 agreeableness and neuroticism. Males had higher testosterone and cortisol levels and lower 2D:4D than females. Digit ratio correlated inversely with salivary testosterone, Machiavellianism, and psychopathy. Testosterone levels correlated positively with cortisol levels and psychopathy and negatively with agreeableness, neuroticism, and Machiavellianism.

CONCLUSIONS

These results provide indications that Machiavellianism and psychopathy (Dark Triad) traits, but not narcissism or Big 5 traits, are linked to markers of prenatal testosterone exposure. Results also replicate sex differences seen in 2D:4D digit ratios, with males having a shorter second-relative-to-forth finger. Links between circulating testosterone, digit ratios, cortisol and personality traits provide further information about potential biological bases of personality.

Second to fourth digit ratio is a predictor of sporting ability in elite Indian male kabaddi players

BACKGROUND

To determine the 2D:4D ratio in elite Indian male kabaddi players and compare them with non-athletes.

OBJECTIVES

Our study was undertaken to find out a possible relation between digit ratio and sporting ability of male kabaddi players. This study also gives an insight into the possible ethnic differences between Indian sports personnel and other populations.

PATIENTS AND METHODS

Both right and left hands of 33 male kabaddi players attending training camp at the Bangalore regional centre of Sports Authority of India were scanned. Lengths of second and fourth digits were measured and their ratio calculated. Age, weight, height and body mass index matched subjects (25 males) who did not participate in any sports formed the control group.

RESULTS

A highly significant difference was found in 2D:4D ratios of both the hands with Kabaddi players having a lower ratio compared to their controls. There was no statistically significant difference in 2D:4D (Δ r-l) between Kabaddi players and controls.

CONCLUSIONS

Kabaddi is an intermediate sport not requiring a high level of endurance but at the same time requires masculine traits because of combating nature of the game. 2D:4D ratios can be used as reliable additional criteria when screening for prospective players to be inducted into the team.