Psychology as a field is one that is constantly becoming out of date. General consensus amongst psychologists often doesn't reach academic text quickly, because of the bureaucracy that exists inside the APA (American Psychological Association). See the controversy around the most recent version of the DSM.

I've observed that academics in the field will often take theory as most likely fact, if only because the actual published academic material hasn't caught up yet, but they've all been to the various conferences that are relevant to their particular field (social psychology, cognitive, etc).

Any study that is citing materials from over 20 years ago is grossly outdated. Many of the materials from even 10 years ago are becoming outdated. And now, more recently, we've started to examine the racial bias that exists in our systems of research, so I expect past material to come under even further scrutiny.