This actually points out something I realized the other day. One of the things that best helps with Prius fuel efficiency is the psychological reward the Prius gives you in the form of the bar chart/MPG reading on the MFD.

It's largely the driving habits of the person behind the wheel the get the best MPG vs. the actual car. It's almost addictive to see the bars hit the 100MPG+ mark on the stretch of road you're driving after you pulse-and-glide your way along. Then again, if the car encourages you to have good driving habits, maybe it really is the car. Hmmm...

Anyway, I think it's interesting the kind of mind games hybrid cars play with you. I'm sure the effect of visual rewards on the driver is intentional in the engineering, which is another reason I find cars like the Prius so brilliant!