Good science is comparative. Because horses are hoofed herd animals, they have much in common with cattle and deer. Because they are mammals, they have much in common with raccoons and dogs. They are animals and so have much in common with octopus, birds and fish. Our lineage defines our form, but our behaviors can often be traced far back on the family tree. When we find common behaviors across different twigs of the family tree, we can know that we have found an ancient behavior and can often learn about one species by looking carefully at another. When a sandpiper, baby raccoon, or horse threaten, they all bend down, assume a snowplow position with their heads, and move forward. Surely animals have been threatening each other for eons. New species do not bother to invent new behaviors when the old ones work perfectly well.
The brains of mammals are very similar, and differ in degree rather than kind.
The human desire to believe that we are the most intelligent species has led to a number of comparisons of brains. Brain size must matter, but our brains are smaller than those of the elephant or whale. Some researchers find pleasure in noting that some parts of our brain are much bigger than the same parts in other animals. For instance, our friend Cowboy Bob reports that “the brain cavity of a horse is filled with a lot more than what we usually think of as the “brain.” Although the space would, in fact, hold a small grapefruit, the cerebral hemisphere — or “thinking” portion of the brain cavity is a lot smaller.”
If horses could talk, though, they might point out that the brain cavity of their skulls is about the size of ours, and that lots of preprocessing happens between the nostrils and the brain, and between the eyes and the brain. If we compare head size of Mr. Horse and Mr. Man, Mr. Horse does just fine.