During a career spanning nearly seven decades, this American academic was esteemed both as a pioneering and influential neuroscientist, examining the physiology and evolution of the nervous system across organizational levels, and as a champion of the comparative approach, studying species from nearly all major animal groups—coelenterates, annelids, arthropods, echinoderms, molluscs, and chordates.

Bullock appealed to the scientific community to look beyond established paradigms in neuroscience, as well as to consider the ecology of an animal when endeavoring to understand its nervous system.

In one influential review he wrote, “Comparative neuroscience is likely to reach insights so novel as to constitute revolutions in understanding the structure, functions, ontogeny, and evolution of nervous systems.

[…] Without due consideration of the neural and behavioral correlates of differences between higher taxa and between closely related families, species, sexes, and stages, we cannot expect to understand nervous systems or ourselves”.

Bullock's doctorate work was performed at UC Berkeley under the supervision of S. F. Light, and focused on the organization of the nervous system (both anatomy and physiology) in acorn worms, generally considered a sister group to the chordates.

This marked the beginning of his studies on simple nervous systems, which he used to explore the neural mechanisms that work together to produce an output in response to a stimulus, both at the physiological and behavioral level.

In one series of famous experiments on the cardiac ganglion in lobsters, Bullock demonstrated that neurons can communicate not just via action potential and chemical synapse, but through non-synaptic interactions without such impulses.

In 1966 Bullock left UCLA to join the University of California, San Diego (UCSD) School of Medicine’s new Department of Neurosciences.

Other than the species previously mentioned, he also studied the nervous systems of corals, sea urchins, spirunculids, Limulus, Aplysia, starfish, rattlesnakes, rays, sharks, porpoises, sea lions, cuttlefish, catfish, sloths, manatees, salamanders, frogs, turtles, hagfish, crayfish, tuna, ratfish, bats, crabs, octopodes, snakes, rats and humans.