It's fairly clear that motorcycle helmets can protect you during a crash. However, many riders point out that they need to be able to see and hear perfectly to avoid getting into an accident in the first place. Any restriction on their senses could make an accident more likely. As such, they don't always want to wear helmets, which they believe make it harder to hear traffic around them and to see what's happening on the road, especially in their peripheral vision.
Is there any validity to these claims?
Not according to the Public Services Research Institute. They reported on a study that examined hearing and sight with a helmet on, and they noted that the impact on the senses from wearing a helmet is "at most, far too small to compromise the safety benefits."
Granted, even that is stated as "at most." There is some thought that a helmet should not impede the senses at all. What they're saying is that, even if it does, the protection benefits are so helpful to a rider's health that they outweigh the very minimal changes in the way that the rider sees and hears the traffic around them while riding.
This is a strong opinion, showing just why helmets are so necessary and why riders need to do all they can to stay safe. After all, you can't predict what other drivers are going to do, and they can very easily cause serious accidents. If that happens and you get injured, whether you had a helmet on or not, make sure you know exactly what legal rights you have.