Last Friday I banned all the other monitors from my desk and wanted to go with a single monitor for a while, because I believed in increasing my ability to focus by doing that.
I am now only working three days with one monitor instead of three and I must admit, yes, it is true. (At least for me)
It's not a big secret that I am easily distractable, so I am trying to avoid distractions at all cost. But for a long time now I always let that happen, for example with having email and slack open on one of the other monitors.
For me this is definitely a big win of productivity and focus. The whole desk got calmer now.
I will share a photo another day.