There was no sense that the wheels in his brain were cranking, but then the questions didn't require much mental machinery.

I leaned the back of my head against the tree trunk and let my mental machinery go.

The phenomenon was like every time since Td first let that relentless mental machinery in my head get its teeth into a problem.

How then are we able to learn and remember, to create new circuits in our mental machinery?

No reason, that is, to do with the quality of their mental machinery.

For once his mental machinery refused to respond.

It would seem, gazing inward, that our mental machinery can determine whether two events are simultaneous.

His mental machinery had gotten some relief that it needed from its constant activity in the conscious state.

Their mental machinery was just like his, also its manner of working.