Research for the past ten years suggests that your "digit ratio" between these your index and ring finger can reveal some interesting tidbits about you:
Your sex. Well, hopefully you don't have to look at your hand to tell if you're a man or woman. It turns out that the basis of most of this dimorphism is due to how much testosterone exposure we had in the womb. Men tend to have a longer ring than index finger (left panel), while women's are generally similar to or shorter than the index finger (right panel).
Fertility. Men with longer ring fingers may be more fertile. For women, it's the other way around.
Heart attack risk. Longer ring fingers, or higher testosterone levels, seem to protect against risks contributing to heart attack.
Income. It seems that the longer the ring finger, the more likely to be aggressive and take risks—the higher, perhaps, the income. Again—testosterone.
Clearly these hormone-related differences must have their basis in the brain. But can our fingers tell us anything about what's going on—or what's to come—neurologically?
Check out this abstract from a 1985 journal publication regarding fingerprint loops and Alzheimer's risk. This study is now 26 years old. I invite my brainy readers to discuss: what are the problems with making these claims? (Hint: the loop thing isn't true!)
Fingerprint dermatoglyphic patterns in 50 patients with presumed senile dementia of the Alzheimer type (SDAT) were compared with a control group of 50 patients with other neurologic diseases and with population norms. Patients with SDAT showed a significantly increased frequency of ulnar loops on their fingertips and a concomitantly decreased frequency of whorls and arches. A pattern of eight or more ulnar loops was found significantly more often in patients with SDAT (72%) than in the control group (26%). Fourteen patients with SDAT had ulnar loops on all ten fingers; this occurred in four patients in the control group. Radial loops on the fourth and fifth digits were more prevalent in patients with SDAT.
Photos courtesy Soda Head and Tholath.
Weinreb HJ (1985). Fingerprint patterns in Alzheimer's disease. Archives of neurology, 42 (1), 50-4 PMID: 3966885