The ratio between 2nd and 4th digit length (2D:4D) may be a negative correlate of prenatal testosterone. This possibility has led to a number of studies of 2D:4D and its relationship with sexual orientation and other sex-dependent traits. At first, 2D:4D ratio was calculated from measurements made directly on the fingers but recently a number of studies have used measurements from photocopies of the hands. Here, we compared finger lengths (2D, 3D, 4D, and 5D) and ratios obtained from these two measurement techniques. Our sample consisted of 30 homosexual men and 50 men and 70 women who were not selected for their sexual orientation. We found evidence that (1)2D:4D from photocopies tended to be lower than that from direct measurements, (2) there were differences in finger lengths such that 2D from photocopies tended to be shorter or equal in length to direct measurements, while 4D from photocopies tended to be longer or equal in length to direct measurements, (3) the sex differences in 2D:4D tended to be stronger for photocopy measurements, and (4) the pattern for length differences across 2D to 5D appeared to be different for homosexual men compared to men and women recruited without regard to sexual orientation. We conclude that there are differences in digit ratios obtained from photocopies and direct measurements, and these differences arise from length differences recorded from the different protocols. Therefore, 2D:4D ratios obtained from photocopies and direct measurements should not be combined within one study nor should they be used together in comparative studies. We suggest that finger length differences between the two techniques could result from the shapes of fat-pads at the tips of the fingers and these may be dependent on sex and sexual orientation.

There is anatomical and physiological evidence that endurance running (ER), i.e., running one or more kilometers using aerobic metabolism, originated early in the evolution of Homo, and the consequences of early selection for ER may be important in modern Homo. Here we examine ER performance in competitive ER. ER is sex dependent such that men tend to run faster than women, and the influence of sex on ER suggests that it may be modified by testosterone (T). It is shown that a putative proxy for prenatal T, the ratio of the length of the 2nd and 4th digits (2D:4D), is correlated with ER. Thus performance in training for ER was associated with high prenatal T, as measured by low 2D:4D, in both men and women. In cross-country races from 1 to 4 miles, 2D:4D explained about 25% of the variance in both male and female ER. Therefore, speed in ER was dependent on a proxy for prenatal T. 2D:4D correlates with performance in sport and exercises, which test a mix of strength and fitness, but the associations are in general quite weak with 2D:4D accounting for less than 10% of the variance in performance. Our finding that 2D:4D explains about 25% of the variance in ER suggests that prenatal T is important in determining efficiency in aerobic exercise. Early populations of Homo may have been strongly selected for ER and high prenatal T. The implications of this for patterns of predisposition to cardiovascular disease in modern Homo are discussed.

The ratio of 2nd and 4th digit length (2D:4D) is sexually dimorphic and may be a correlate of prenatal sex steroids. 2D:4D is often calculated from measurements of photocopies of fingers. However, 2D:4D from photocopies is lower than 2D:4D from direct measurements of the fingers. A new and promising source of 2D:4D measures is self-reports from Internet studies. This necessitates self-report of direct finger measurements and such measurements may be unreliable. In the present study, we compared 2D:4D from self-reported finger lengths measured directly from the fingers (S-R 2D:4D) and experimenter-measured finger lengths from photocopies of the fingers (photo 2D:4D). There were 329 participants (77 men, 252 women) recruited from a first-year undergraduate psychology pool. Compared to photo 2D:4D, (1) S-R 2D:4D tended to include some extreme values; (2) S-R 2D:4D was higher; (3) S-R 2D:4D showed weak similarities which increased when extreme values of S-R 2D:4D were removed; (4) photo 2D:4D and S-R 2D:4D showed lower values for males compared to females but the dimorphism was significant for the former but not for the latter. We conclude that, insofar as S-R 2D:4D has similarities to 2D:4D from Internet studies, the 2D:4D from Internet studies will show extreme values which should be removed, mean 2D:4D will be higher than from photocopy studies, and the sexual dimorphism will be weaker than in photo 2D:4D. We suggest that large samples are necessary in Internet studies of 2D:4D because measurement error will reduce effect sizes.

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Background ‘Diabulimia’ is the term given to the deliberate administration of insufficient insulin for the purpose of weight loss. Although Diabulimia can be life-threatening and prevalence rates in diabetes are high, there is a lack of research for how to effectively support people with the condition. This exploratory study aimed to provide much-needed information to healthcare professionals and guide the focus for future research. Methods Forty-five individuals with Type 1 diabetes mellitus (T1DM) and a history of insulin misuse completed an online questionnaire. This included an assessment of their eating disorder psychopathology with the Eating Disorder Examination Questionnaire (EDE-Q) and 16 open-ended questions exploring their experience of Diabulimia. The responses to the open-ended questions were analysed using thematic analysis. Results The average global EDE-Q score was 3.96 (1.21), which is consistent with eating disorder populations. Common themes identified were concerns about weight, difficulty coping with diabetes, past trauma, and the importance of relationships. Experiences with health professionals were overwhelmingly negative. Most participants had experienced serious medical intervention due to Diabulimia and were fully aware of the consequences of insulin restriction. Conclusions Overall, individuals believed that a greater awareness of Diabulimia and more training for healthcare professionals is needed. While education on insulin misuse may be a necessary first step in treatment, psychological support is crucial. To deliver effective treatment, clinicians should be aware of the specific issues facing those with Diabulimia. The current study identified themes that clinicians may find useful to consider.