check this article for example: http://geronj.oxfordjournals.org/con.../P113.abstract (i can't get the whole article without library access).

they say the peak performance is mid-late 20's. this quote in the abstract "...and the relative roles of biology and learning are discussed as determinants of peak performance. " is the point i was making in the earlier post. the biology will be a downward trend as age increases and learning should increase with age. what we consider "peak performance" is determined by that balance of decreasing biological ability with increased learning/experience.

here is a link that's not as scientific that mentions just the physiological aspect: http://www.cptips.com/age.htm