You don't need a brain to be intelligent. A biologist explains

[BidenPresident]

Research led him to suspect that the intelligence of living things lies outside their brains to a surprising degree. Substantial smarts may be in the cells of a worm's rear end, for instance. “All intelligence is really collective intelligence, because every cognitive system is made of some kind of parts,” Levin says. An animal that can survive the complete loss of its head was Levin's perfect test subject.

https://www.scientificamerican.com/...-and-solving-problems-simple-cells-can-do-it/

 

[AProudLefty]

Research led him to suspect that the intelligence of living things lies outside their brains to a surprising degree. Substantial smarts may be in the cells of a worm's rear end, for instance. “All intelligence is really collective intelligence, because every cognitive system is made of some kind of parts,” Levin says. An animal that can survive the complete loss of its head was Levin's perfect test subject.

https://www.scientificamerican.com/...-and-solving-problems-simple-cells-can-do-it/

We see that in jellyfish.

 

[T. A. Gardner]

We see that in jellyfish.

And most college students...