If zombies are attracted to non-environmental movement, then wouldn't zombies be drawn to each other? Is that why more zombies come when they find food?
Why don't zombies try to eat each other? Do humans smell different perhaps?
If 'runners' are alive humans with infected brains, why don't zombies attack them? Do they attack them but the runners fight them off?
I would like to know your opinions! I can't quite figure this out...