Great article in the NYT about how people make judgments and rationalize them. We process information so quick that we size things up in nanoseconds. Interestingly the article notes this about ageism:

AGE plays a role in forging stereotypes, too, with older people traditionally seen as ‰ÛÏharmless and useless,‰Û Professor Fiske said. In fact, she said, research has shown that racial and ethnic stereotypes are easier to change over time than gender and age stereotypes, which are ‰ÛÏparticularly sticky.‰Û

We have a long way to go folks to break the stereotype of what it means to grow old and be productive.