Michael O'Bryan, Wired.com:

The common perception is that the young are better suited to come up with novel ideas.  There is also a historic stereotype of the older worker as a “fish out of water”, unable to deal with innovative environments.  This stereotype is seen in popular culture, such as the 2013 movie “The Internship” where two 40-year-olds struggle with the loose and creative atmosphere at Google.  Rapid changes in technology influences the perception of older workers being unable to keep pace with it, and creativity, in general, is seen as a young person’s game.

The perception of the lack of creativity in older employees, like stereotypes in general, is not supported by research.  Reviews of hundreds of studies, indicates that age has no bearing on creativity.  As reported last year, studies have shown that creative ability in people peaks later in life.  For example, physicists make their greatest discoveries around age 48, and painters are at their creative best around 42.