This is really just a subset of all the other kinds of calls on this list, but it is one that is worth singling out. The Momentum Swing/Reversal occurs when the official gets caught up in the flow and pace of the game and starts making calls based upon… well… momentum.
This can be a tricky one to identify as it can go either way (giggity) by either being a call that goes for or against the team with all the momentum. Usually, though the Momentum Swing comes during a run as an attempt to make the game closer.
So, if a team is down by 25 and on a legitimate 10-0 run, sinking everything, you can expect that if there is even mild contact at the hoop and the shot is missed, the ref will call the foul because that team has all the momentum and is likely playing the better, more aggressive brand of basketball.
Conversely, if the game is tied and a team goes on a 15-0 run where the other guys look lost, you can expect a ticky-tack call, or a random travel violation as an attempt to halt the runaway momentum and give the other team a chance to get back in it.
And if you are up by more than 20 in the fourth quarter you may as well never expect to get another call again.
This should not be the job of the officials. They really should have no concept of what the score is or who is playing well when making each call. The score and the dynamics of the game should not affect what is and is not a foul. Unfortunately, it seems that way too often and then announcers explain, “the calls go to the more aggressive team!”
The calls should go to the team(s)/player(s) who deserve them and nothing more.