Well, it depends on the definition of the term ‘brain’.
According to Merriam-Webster, brain is the central processing unit (organ) whose function is to control functionalities of a living body.
So, does this mean some animals have multiple brains?
When defining the term ‘brain’, we tend to use our human body as an example of reference. This is because our brain controls everything our body does. It’s literally the central processing unit. And it’s only one.
Therefore, we expect other animals to animals to have a similar brain, whose main function is control — through the nervous system and neurons.
However, with some animals, and in some very rare cases in human be, the organ responsible for centrally controlling the body are situated in different places. Thus making up for multiple brains.
This is commonly known as polycephaly, or the occurrence of multiple heads within one body. It’s a very rare condition, but this can be categorized as ‘multiple brains’ in an animal.
As for animals with multiple brains, such as worms and insects, their ‘brains’ work by subordinating other brains, known as ganglia. These are separate central organs with neurons and nervous systems fulfilling the brain’s functions of control and coordination.
From an anatomical point of view, no animal has multiple brains, but physiologically, and putting aside polycephaly, there are a number of animals with multiple brains.
I hope that clears things up and isn’t confusing anymore. We can technically say that certain animals have more than one brain. Examples of animals with multiple brains include:
- Cephalopods e.g. octopus, squids and cuttlefish
- Insects e.g. cockroaches, grasshopper, bumblebee, and mosquitoes
- Annelids e.g. leeches, flatworms and silkworm moths.
- Gastropods (snails/slugs)
- Dogs, Monkeys, Cats, and even some human beings — but these are mainly due to polycephaly, a rare genetic anomaly when an animal is born with two heads. Which means two brains.