The topic is enormous, but I have pulled together 16 posts from this blog that inform us a bit about intelligence.
Should general counsel try to hire the smartest lawyers they can find? Intellectual elitists regard a fine mind to be the most important determinant of success (See my post of Jan. 1, 2006: IQ tests predict work performance ten times better than do personality tests; Jan. 14, 2007: IQ as a predictor of job performance; Aug. 28, 2008: hedge fund managers and SAT scores of alma maters; and May 13, 2005: competency, IQ, personality, and emotional intelligence.).
People suggest that it may even be possible to increase one’s IQ (See my post of Jan. 15, 2006: how to increase IQ; Nov. 6, 2007: the Flynn effect of rising IQs; and June 12, 2005: ten years to become an expert.). Others argue that IQ is primarily determined by inherited genes (See my post of Feb. 1, 2007 #3: height and intelligence.).
Some people maintain that multiple kinds of intelligence exist (See my post of Jan. 1, 2006: executive intelligence; Nov. 13, 2005: broader intelligences; and Dec. 3, 2007 #4: emotional intelligence with 5 references.).
Whatever you think of cerebral horsepower, sharpness of even a boffin suffers when distractions surround the thinker (See my post of Oct. 12, 2006: interruptions degrade thinking; July 14, 2005: technology distractions; and Feb. 20, 2008: proficiency at multitasking is correlated with IQ.).
Some second-order effects of intelligence may include assumed correlations between success and brains as well as a propensity to caution (See my post of May 18, 2007: profits per partner and intelligence; and Dec. 2, 2007: intelligence and caution.).