Roundabouts have an extra mental tax on drivers

So, just like the rest of driving?

Freeway on-ramps, stop lights, pedestrian crossings, bike lanes, one way street... Lots of things are harder mentally until you learn to get used to them.

Roundabouts force you to slow down, however, which is why I think they get such a big backlash at first. But in reality, when built in the right areas, they improve overall traffic flow.