A discussion list to which I belong has recently been discussing the phenomenon? myth?? that great scientific discoveries (in particular areas) tend to be made by young scientists. The famous physicist Murray Gell-Mann, commenting on this, apparently remarked that, in his own field of theoretical particle physics, this was true because the field was so new; in the life sciences, so much was known, that " It took years of study and rote memorization for an aspiring scientist to master what was already known. By the time a researcher was ready to make an original contribution, he was probably well advanced in his career."

This illustrates an important principle in memory and aging that tends to be overlooked. Yes, younger brains are faster, probably more flexible, with perhaps more working memory capacity - but older brains can make up for that, with the fruits of experience. WM capacity is one example of that. Say, at 25, you have a capacity of 8 "units"; say at 75 that has dropped to 6 (this is a simplistic way of representing a complex situation, but I'm trying to make a point here). A "unit" can be a single datum, such as "4" or a complex chunk, such as "The quality of mercy is not strained, it droppeth as the gentle rain of heaven upon the place beneath". The flexibility of the "unit" says everything about the value of strategies - memory strategies can turn complex and lengthy conglomerations of information into single "chunks" / "units". An experienced 75 year old, with expertise in a particular field, can have developed very complex chunks and thus, despite the drop in capacity, easily out-think a 25 year old.

(By the way, if you want to read the classic paper on WM capacity, by George Miller on the "Magical Number Seven", you can read it here.)