The study revolved around the reaction of 137 Princeton University undergraduates, who were shown a video of someone who would be their partner in a trivia contest talking about themselves. These potential partners were all white males, but were either 25, 45, or 75 years old. Each one adhered to the same script in talking about himself, except that half the time the person indicated that he was the kind of person who shared his wealth with relatives (a "compliant" personality), and the other half of the time he said he had no obligation to share with relatives. For the 25 or 45 year old subject, it made no difference whether he was generous or not, but the 75 year-old who indicated he was not generous (this was characterized as being “assertive” by the researchers) received a very high negative rating from the undergrads.
The lesson- if you are an older worker, and you want to speak your mind to your manager, you should expect some fall out. Does this equate to age bias? Unquestionably, but it appears to be something that is fairly subtle, although strongly ingrained. Per my standard advice, the key to combating this type of bias is to focus on performance specifics, rather than some unspecified type of gut reaction to a particular individual. My guess is that it's easier for people to recognize visceral reactions triggered by race or gender, but it's clear from this study that age can generate just has negative a response.
There is a lot more research developing on the this type of bias, since these age discrimination claims are the fastest increasing type over the last few years. That trend should continue as Boomers move into the Social Security zone, but find it increasingly necessary to work.