But is it because of the smaller body sizes using less brain for the bodily functions? I don't think so.

edit: I frankly don't get the point with EQ. If we had to make a computer control for bodily functions (e.g. to grow ethical meat), we could do with a weaker cpu for larger animals because they work slower. It just doesn't make sense that body size would be using up brain to control it, irrespective of the composition of that body.