All the time. Witness the effects of cellphones/children/food/spilled food/makeup/jarring news/exciting music/significant others/attractive people/gawking at random bits of interest. Also, brake-checking just cause' and for insurance fraud.

If what you're proposing is that "success" in this experiment is that every Tesla now drives at least as well as the absolute worst-case human driver, then you've pretty much articulated why this experiment is so dangerous.

The thing is these are not the "absolute worst-case human driver", these are the absolute average human drivers.

People get easily distracted, get excited, get tired, all of which are propitious to bad decision-making.

Many human drivers are downright dangerous, but that's not a reason to add dangerous machine drivers on the road, either.

The adaptive cruise control in my Honda is also bad about braking without good cause. Of course, they don’t market it as “self-driving”.

Automatic emergency braking also has false positives.