An interesting article that suggests the obvious reason that people are afraid of being injured, which is why they don't step in to help people being attacked - is not actually one of the main reasons!!
BBC News - Fight or Flight
Not listened to the Radio 4 programme yet but looks like it might be interesting
Radio 4 - Fight or Flight
BBC News - Fight or Flight
Not listened to the Radio 4 programme yet but looks like it might be interesting
Radio 4 - Fight or Flight