The body is the ultimate giveaway. You can look at even a person's thumb or toes and know everything about their intellect or level of sophistication. The body is of fractal design, and its symbolism is reflected symmetrically throughout its different features. Short and wide, stubby thumbs are a primary predictor for mental retardation. Square-shaped nails that are sunk into the flesh are also a sign of partially incestuous relationships somewhere down the family tree. Narrow and elongated is a sign of heightened intellect and neuroticism, but if the skin is overgrown around the nails, that's a sign of narcissism, or if the nail is much narrower than the thumb. Wholly protruding but symmetrical nails are a sign of simple-mindedness, lack of creative input or vision, especially if they outline the thumb. Just slightly elongated nails with a perfect mixture of over-the-skin and under-the-skin is the best sign for balanced temperament and intellect. Generally, most of the dumbest people you know will 99.99% of the times have width over length on their thumbs. Fleshy, stubby, almost underdeveloped. What’s the reference for knowing whether your thumbs are long or short? There is none. Until I make one. :)