Starling Fitness points out a BBC Health article that studied the amount of electrical activity generated when subjects mentally focused on the muscle they were using increased.

This indicates that you are actually able to use your mind to increase your lifting ability.

From the BBC:

When subjects were asked to focus on what their muscles were doing and how they were working there were significantly higher levels of electrical activity.

But when they were asked to visualise lifting the weight, electrical activity was lower.

Something to think about when you’re on your last set of a lift and trying to push through. Focus on the muscle for that extra boost.