It's not directly obvious that sitting in a certain way activates the brain more (it probably does if any balance center is activated), but sitting in better po

It's not directly obvious that sitting in a certain way activates the brain more (it probably does if any balance center is activated), but sitting in better posture does have a lot of benefits from breathing better, not having muscles worn in overdrive to try to compensate and so on. Playing chess in one leg is a curious thing to me, I think it would initially affect the player's performance but that's just a guess.