In the board game Go, there are two basic styles, high and low. "High" is all the rage for about ten years, until people have forgotten how to play "low." Then "low" gets "rediscovered," and people win tournaments with itfor about ten years until high becomes popular again.
In bridge, people used to "underbid" in competitive situations. That is, they failed to overcall, make takeout doubles or "balance," even when it was to their advantage to do so (that is when the penalty for going down was less than the opponent's probably game). Then people learned these techniques and did them a lot. Have they ever overdone such competitive techniques (that is, give away more games or gone down more than they should have)?
Have people made "mistakes" in the past that would be considered such by today's standards, even though they may have been acceptable bids at the time they were made?