![]() Another study 32 investigated the relationship between the 2D:4D and a testosterone change after a combined physical exercise (repeated sprints), and psychological task (watching an aggressive movie) among 24 participants (12 males and 12 females). This association was moderated by the left (but not the right) 2D:4D, meaning the lower the left 2D:4D, the greater change in testosterone. Results showed that testosterone levels were higher after watching an aggressive video in comparison with a blank screen condition. 45 males watched an aggressive video or a blank screen in a cross-over design. 34 conducted also a similar research, but using psychological stimuli. Results showed that there was no association between pre-exercise testosterone level and the 2D:4D, but the testosterone change was significantly correlated with the right (but not the left) digit ratio, meaning the lower the right 2D:4D, the higher the testosterone change under a physical effort. 33 research, 25 professional rugby players performed a physical activity, resulting in a raise of the testosterone level. physical exertion, or aggressive context) situation was measured 20, 32, 33, 34, and they have led to equivocal results. However, there were only four studies in which the relationship between the 2D:4D and the testosterone change in response to a challenging (i.e. One of such hypothesis is that the organizational effect of the exposure to androgens in uterus might not result in the higher adult testosterone level but rather in greater hormonal reactivity to a situation perceived as a challenge, i.e. 15 found no such association.īecause there are many mixed findings on the mechanism of the observed differences in digit ratios 12, 13, 14, 28, and at the same time, there is a constantly growing body of literature showing positive associations between the 2D:4D and, for instance, psychological or physiological 29, 30 characteristics, new hypotheses explaining the potential relationship between the 2D:4D and aforementioned traits are being suggested. Interestingly, only a few studies reported a negative link between the 2D:4D and adult sex hormone levels 5, 18, 19, 20, 21, 23, whereas a meta-analysis conducted by Hönekopp et al. Even more speculative is that some researchers presume that the low 2D:4D may reflect higher adult testosterone 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27. Similar, mixed results have been found in experimental studies on animals 12, 13, thus, it is not surprising that such links are perceived as questionable and unclear 14, 15, 16. ![]() However, correlational studies on the relationship between the 2D:4D and the prenatal testosterone level conducted on human fetuses brought conflicting results 6, 7, 8, 9, 10, 11. Hence, the 2D:4D is perceived as an index of prenatal testosterone level. The 2D:4D is said to be directly connected with the exposure to androgens in the uterus (with the lower digit ratios associated with the exposure to higher levels of testosterone, and higher digit ratios associated with the exposure to lower levels of testosterone). Manning and colleagues 5 suggested that the difference between the 2D:4D among men and women develops during gestation under prenatal sex steroids control. Since then, researchers have been interested in the origins and implications of the 2D:4D sexual dimorphism. The ratio between the length of the 2 nd and the 4 th finger (2D:4D) has been reported to be smaller among men compared to women (men have longer the 4 th finger than the 2 nd finger) (but see also: 3, 4). Further studies provided evidence that men and women vary when it comes to the magnitude of this difference 2. More than 100 years ago, a difference in the length of the 2 nd, index finger (2D) and the 4 th, ring finger (4D) has been described 1.
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