I learned a lot from the Seattle Longitudinal Study. This diagram basically sums up their findings: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1474018/figure/F... Also, they mentioned that if you correct for the loss in perceptual speed that comes with age, the drop is not as significant. I interpret this as, "If we give elderly people as much time as they need to take an IQ test, their performance will be relatively close to that of 20-somethings taking the same test under the same conditions." (I may be wrong, but that's what I would like to think.) I also found a study by UVA that is looking for participants, in case anyone is interested: http://faculty.virginia.edu/cogage/