How does cognitive distraction (e.g. talking on a hands-free mobile phone) impair driver reaction times compared to driving with full focus?

1. A demanding hands-free conversation can consume attention, delay hazard detection, narrow scanning, and slow the driver's response even though both hands remain available
2. Hands-free calling is equivalent to silence because the driver does not look away from the road
3. Only manual phone handling can delay hazard detection; conversation complexity has no effect
4. A familiar caller cannot distract an experienced driver, even in demanding traffic