A study conducted by Korean Urologists from Gachon University and reported in the Asian Journal of Andrology finds that the ratio of the length of a man’s index finger (also known as your “pointer finger”) compared to his ring finger is linked with penis size: The lower the ratio, the longer the penis.
Research conducted on 144 Korean men who were hospitalized for urological surgery measured the patients’ penile length — flaccid and stretched — just after they went under anesthesia for their operations. In an effort to prevent bias in measurement, a different researcher measured each man’s finger lengths.
The data suggests that those with a lower ratio — whose index finger (or second finger, 2D) was shorter than the ring finger (or fourth finger, 4D) — had a longer stretched penis length, which is well correlated with erect size.
“Based on this evidence, we suggest that digit ratio can predict adult penile size,” the researchers, led by Dr. Tae Beom Kim of Gachon University in Incheon, Korea, wrote.
According to Time.com, previous studies have linked the so-called “2D:4D ratio” of finger length with exposure to the sex hormones estrogen and testosterone in the womb. So it’s plausible that the same exposure may affect penis length.
Wrote Time’s Maia Szalavitz, a neuroscience journalist, “Higher testosterone levels during fetal development are associated with a lower 2D:4D ratio, while higher estrogen levels are connected with a higher one. Most men have index fingers that are shorter (low ratio) than their ring fingers, while most women’s index fingers are the same size or longer (high ratio) than their ring fingers. Research has shown, however, that lesbians and female-to-male transgendered people are more likely to have more ‘male’ ratios.”
This is not the first time finger-length ratios have been linked with other characteristics: in both males and females, lower ratios are connected to better athletic performance. For example, another study on men indicated a lower ratio is connected with better performance in high-frequency financial trading, and associated it with better performance on medical school entrance exams.