"The available research indicates that cell phone use while driving, whether it is a hands-free or hand-held device, degrades a driver’s performance. The driver is more likely to miss key visual and audio cues needed to avoid a crash. Hand-held devices may be slightly worse, but hands-free devices are not risk-free."
Though it doesn't link to any studies and I'm too lazy to go searching, so if you want a primary source you'll have to find it yourself...
https://one.nhtsa.gov/Driving-Safety/Distracted/Policy-State...
Just like talking to other people in the car or doing anything else other than driving. I know that I will take a driver getting their messages read out to them over a driver who takes their eyes off the road and glances at the phone. Good is the enemy of the perfect, and I would rather take an attainable good over an unattainable perfect.
No that's not true, talking to other people int he car is not associated with reduced safety.
Probably because the other people in the car are also partially watching the road.
Mazda will walk this decision back as soon as they realize how much money it will cost them... which is a lot.
I thought I had read a study about talking to people in your car versus drinking, but here's a similar one with talking on a phone versus being drunk: https://www.ncbi.nlm.nih.gov/m/pubmed/16884056/
It's hard to explain, but I would say my attention is unfocused and broad. I don't know if this is ultimately safe, but I've never had an issue with it.
OTOH, I also evaluate and will not talk if I don't feel comfortable (poor road conditions, etc).