A quote from the Justo Gallego thread: I have a feeling that head size is not a sole indicator of intelligence, its the proportion of head to body as well as head size. For example (just for an example, this might not be scientifically correct) a body that is 5'5" (165cm) tall and 56 kilograms (123 pounds) will need a brain of 1000cc to possess an IQ of 150. A body that is 6'2" (188cm) and 98 kilograms (216 pounds) will need a brain of 2000cc to possess the same IQ. I think I have said this before: do not just read the face and the head, but also the body. I am a 5'10" (178cm) and 65 kilograms (143 pounds) Asian guy. Every day, I see throngs of white and Pacific Islander guys who are bigger and taller than me, and probably have bigger heads than me. However, they are not as smart. And there are people who are smaller than me who can have a conversation with me about complex topics. The next time you try to read someone, you might want to take into account his/her body size.