Strong feelings tend to generate contradictory research for two obvious
reasons. First, systematic observation sometimes fails to confirm
evocative anecdotes, which may be evocative because they resonate with
stereotypes rather than because they genuinely confirm experience.
Second, even systematic observation can be misleading, if you don’t
make the right observational distinctions or don’t control for the
context in an appropriate way. When the emotional stakes are high,
people should in principle be especially careful not to overinterpret
or overgeneralize their findings, but in practice, the opposite is
often true.

via Language Log