Small amounts of psychedelics, often below a threshold that would make the user feel significantly altered, are said to be a useful cognitive and mood enhancer. The Plan to Prove Microdosing Makes You Smarter describes the Beckley Foundation's plan to test how well people do on the task of playing the game Go while using microdoses of LSD.
I have one data point for this. Back in the day, several decades ago, during my one and only experience with LSD, I played the arcade game Asteroids. It was a strange experience because it didn't seem like "I" was playing. I was looking at the screen, my hands were touching the controls and moving, but it was as if "I" had no part in it. It was just happening as I watched, there was no conscious intent, cognition, planning, or strategy. It was just happening. And I got my highest score ever, before or since, by about 30%. I think sometimes it can be helpful to get the conscious mind out of the way and just let the underlying mind do what it does without interference.
In my own experience, which is maybe unique in a way, I don't particularly care for microdosing. Once I became "good" at meditation I became much more sensitive to psychedelics. My standard dose became on average a tenth of what it was before. And when I microdosed, even down to as little as 1/200 of my previous standard dose, I noticed it. In my case I'd just as soon do without it, or go to my "full" dose rather than go halfway.