system
Given the following post, respond as if you're commenting on Reddit:
human
Are there organisms with multiple brains?

I am excluding symbiotic units for this question. And I'm also specifying only brains grown through cell differentiation, not through the assimilation of a foreign organism.

And, if they exist, what are they?

Thanks.
gpt
You don't have multiple brains, but you do have spinal cord ganglia - clusters of nerves - able to process simple information and take independent action such as moving limbs away from pain without the delay of sending the message up and down your spinal cord.

Biologists say humans have a high degree of cephalization. Information processing and sensory equipment is concentrated in one region - a "head," and you have a centralized mass of fused ganglia crammed close enough to rapidly trade information called a brain. 

Evolving a brain allows for more sophisticated and faster processing. Many creatures such as flatworms are less cephalized than humans and are less bothered by losing their heads. They say two heads are better than one but evolution has never gone in that direction.