system
Given the following post, respond as if you're commenting on Reddit:
human
[General] How do zombies differentiate human from zombies?

Just started the series and Im full pf questions.
If the zombies are dumb, shouldn't they not know the difference what a human or zombie is?
gpt
Depends on the setting, and cause of the zonbie. 

Magical zombies are typically under some sort of control,  and react more to the edicts of their creator than anything.  Even spontaneous magical zombies are usually able to differentiate between the animating magics (Necrotic, Dark Magic, Negative Energy, etc) and seek out sources of actively living magic. 

Bological zombies, likewise, typically have ways to differentiate between infected and uninfected. Being able to identify the viral or parasitic presence in another os essential to minimising wasted energy in trying to infect an already infected individual. So they can detect sufficent quantities of either their own infectious agent, or undesirable elements in a prospective host, typically via smell.