What's the point of left-handedness? Genius is an outlier, as much as mental retardation. While the strict definition will always be colloquially defined, I would say that a genius is more commonly used to define people who are not completely socially retarded (autism) that have exceptional mental functioning. While autism has extraordinary abilities of recall and recitation, they are generally inept at true genius, i.e., synthesis of concepts and the advancement of knowledge. For those who can recite entire pieces after the first hearing on the piano, or those who can paint quite well, their performance tends to be more technically competent yet lacking in warmth and personality. This, I think, is the key to understanding and differentiating the qualities of just talent or skill and that of genius. At first we tend to look at geniuses as being of Einstein's and Erdos's ilk, and only later on in this introspection do we tend to acknowledge the ability of other accomplished persons such as musicians and artists as being geniuses. Jimi Hendrix, a personal favorite, may not have solved any physics problems but he has forever colored the landscape of popular music and will probably do so for as long as Western Civilization remains solvent, much as Shakespeare has remained a heavy hitter in the written word (in any language). Hendrix had the hands, as well as the innate musical ability, that sets him apart from the legions of pickers copying his style. Some people have a genius or charisma for leadership, and can automatically take the upper hand in any social setting. These types of people have no fear about public appearance and speaking, a task the average person fears almost as much as death. On emotional intelligence and logical intelligence, I find that the people who are generally "smart" and "rational" tend to have longer fuses, are less selfish (abstraction), and are less influenced by base emotions, which is what I would consider emotional intelligence: maximizing the good, while minimizing the effects of- and healthily acknowledging- negative feelings. In close, I would argue that genius or GI is going to be mostly genetically-based, though the expression and devolopment of this ability into a usable skill is going to be somewhat dependent on nurturance. A study published in JAMA correlates age of breastfeeding weaning with intelligence, for example.