Seen a photograph of starlings when the flock takes on the silhouette of a giant bird. I've always been fascinated by that kind of (apparent?) collective intelligence. There's seemingly no leader, but from the interactions of swarms of independent actors emerge (what seems like) a larger mind. Surely we humans exhibit such behavior also, when seen from a certain elevated perspective like statistics.
Ooh boids, yes! One of my favorite books is Vehicles: Experiments in Synthetic Psychology. I learned about it from another favorite, Nature of Code, which has a great list of related books. https://natureofcode.com/resources/#further-reading