Bob, muscle memory refers to the interconnect between the portion of the brain that commands the action and the muscle that actually performs the task. There is a feedback loop between the two that tells the brain what the muscle is doing. So, yes, in a sense your muscles do have brains in them. Practice refines the action so that the feedback loop tells the brain if the muscle is performing the task correctly. Pilots rarely switch tanks incorrectly when that is the only action being performed. It happens when there is a distraction, or other tasks demand attention at the same time. Yars is correct that using a checklist to put things in the proper position well in advance will almost always guarantee that the fuel selector is in the correct position. It’s those last minute distractions that will get you.