Hands may say more about their owners than commonly thought, especially in the case of men.
Men whose index fingers are shorter than their ring fingers may have longer penises, according to a South Korean study published in the Asian Journal of Andrology.
"According to our data ... the shorter index (second) finger than ring (fourth) finger you have, the longer stretched penile length you have," wrote Tae Beom Kim at the urology department of Gachon University Gil Hospital in Incheon, South Korea, in reply to questions from Reuters.
Previous studies have shown strong evidence that prenatal testosterone may determine finger development as well as penile length, a relationship that Kim and his colleagues launched a study to focus on.
The study involved 144 men suffering from urological problems that did not affect the length of their penis, which was measured under anesthesia.
The measurements were later compared to the difference in length between their second and fourth fingers on the right hand. Previous studies have shown that the right hand may be more sensitive to the influence of testosterone.
The so-called "digit ratio" in this study refers to the length of the index finger divided by the length of the ring finger. The lower the ratio, the study suggests, the longer the penis may be.
The findings offered "circumstantial evidence that prenatal testosterone is responsible for both traits (penile length and digit formation,)" said Denise McQuade at Skidmore College in New York, who was not involved in the study.
"Digit ratio is non-invasive and easy to measure, yet may provide clues about an individual's prenatal history. Thus, combined with other information, digit ratio offers the potential for clinical usefulness," wrote McQuade in an email reply to questions from Reuters.
Female index and ring fingers tend to be about the same length, she added.
A study last year said that men with long index fingers have a lower risk of prostate cancer.
Researchers at Britain's Warwick University and the Institute of Cancer Researcher found that men whose index finger is longer than their ring finger were one-third less likely to develop the disease than men with the opposite pattern of finger length.