Every working day I am puzzled by this: On my way to work, I cross a bridge, then get on a four-lane limited access highway (not quite interstate quality). After a couple of miles, this highway merges into an interstate. We come down the ramp and do not have to change lanes, because at this point the interstate goes from two lanes northbound to three lanes northbound.
Yet, every day, I see persons come down the ramp. There is no traffic in the (new) right lane. So they automatically merge to the left into the center lane and proceed to drive slower than anyone else.
Anyone who can explain this behavior is ready for a Ph. D. in psychology.