How does conversation affect a driver’s ability to react to hazards?

When a driver engages in conversation, particularly if it is an involved or distracting discussion, it can divert their attention away from the road and the various hazards present in the driving environment. This distraction can result in slower reaction times because the driver's cognitive resources are being split between the conversation and the task of driving. When focus is impaired, the ability to notice and respond to hazards is diminished, leading to an increased risk of accidents.

The other options are less accurate in this context; speeding up reaction times or increasing alertness is generally not a result of distraction. In fact, being overly engaged in conversation can lead to a lapse in awareness, making it more difficult for a driver to react appropriately to unexpected changes on the road. Therefore, the impact of conversation is predominantly detrimental as it shifts focus and dilutes attention needed for safe driving.