Are you masculine or feminine?

Besides genitalia, relative finger length is the only physical trait at birth that's different in males and females. While still in the womb, the growth of our finger digits is affected by the sex hormones testosterone and estrogen. These hormones also have an effect on our brains.

So how to check? Males tend to have a ring finger that is longer than their index finger (average: 1 to 0.96 ratio), while females typically have index and ring fingers of the same length.

John Manning, a biologist who first identified the significance of 'finger digit ratios', says that "females with masculine digit ratios have more masculine behaviors...males with a typically female ratio exhibit more typically feminine behaviors." Boys with female-type finger lengths tend to be more emotional and sensitive. Girls with the male-type finger lengths tend to be more hyperactive and more predisposed to autism. Lesbians are also more likely to have this finger ratio. Some other characteristics possibly associated with these ratios are musical and sports aptitude; on the negative side, risk of early heart disease and breast cancer.

Read the Psychology Today article

A glimpse of Manning's book