The second to fourth digit ratio and variation in the androgen receptor gene
Section snippets
Methods
In this preliminary study, we chose to restrict our sample to men. The AR is an X-linked gene. Males have one copy of the gene and females have two. Therefore, in males, we can be sure which AR is activated, in females we cannot. Our participants were 50 men (49 Caucasian participants and 1 subject of Caucasian/Chinese origin), with a mean age of 32.63±14.17 years, recruited from a Liverpool running club, a tennis club, and students and staff of Liverpool University. The study was approved by
Results
We found high and significant intraclass correlation coefficients (r1) between our first and second measures of 2D:4D (right-hand r1=.96, F=51.3, P=.0001; left-hand r1=.96, F=45.46, P=.0001). These values of r1 are not unusually high for 2D:4D ratios measured directly from the fingers (Manning, 2002). We concluded that our measures of 2D:4D reflected real differences between subjects.
The mean 2D:4D of the right hand was 0.977±0.04 and that of the left hand was 0.964±0.03. Similar male means
Discussion
We have found significant positive associations between CAG number of the AR, an inverse measure of sensitivity to testosterone, and right-hand 2D:4D and Dr-l. These relationships were in the expected direction and indicate that low right-hand 2D:4D and low Dr-l are associated with high sensitivity to testosterone. The sexual dimorphism in 2D:4D is determined early so an AR/2D:4D association suggests that the finger ratio is a correlate of sensitivity to prenatal testosterone. The relationships
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