Other Minds

When we try to compare one animal’s brainpower with another’s, we also run into the fact that there is no single scale on which intelligence can be sensibly measured. Different animals are good at different things, as makes sense given the different lives they live. An analogy can be drawn with tool kits: brains are like tool kits for the control of behaviour. As with human tool kits, there are some elements in common across many trades, but much diversity also. All the tool kits found in animals include some kind of perception, though different animals have very different ways of taking in information. All (or almost all) bilaterian animals have some form of memory and a means for learning, enabling past experiences to be brought to bear on the present. The tool kit sometimes includes capacities for problem solving and planning. Some tool kits are more elaborate and expensive than others, but they can be sophisticated in different ways. One animal might have better senses, while another may have more sophisticated learning. Different tool kits go with different ways of making a living.

Some philosophers have always disliked this obsession with sensory input, with receptivity, seen in theories of the mind. But their response was to reject the importance of input in a wholesale way, and to try to tell a story about the self-determining organism, about the subject as source, imposing itself on the world. This is a kind of overcompensation, as if philosophers are only able to concentrate on one side at a time. It is a big thing, apparently not easily achieved, to accept that there is traffic, a to-and-fro.

In everyday experience there are two causal arcs. There is a sensory-motor arc, linking our senses to our actions, and a motor-to-sensory arc as well. Why turn the page? Because doing so will influence what you’ll see next. The second arc is not as tightly controlled as the first, because it extends into external, public space, rather than remaining inside the skin. Perhaps as you turn the page, someone grabs the book, or grabs you. The sense-to-motor and the motor-to-sense pathways are not on a par. But the neglected junior partner, the effect of action on what we sense next, is surely important. This, after all, is why we do much of what we do: to control what our senses will encounter.

Philosophers often use the metaphor of a stream of experience. Experience, they say, is something like a river in which we are immersed. This image is quite misleading, though, as the flow in a river is almost entirely outside our control. We might change our location within the river, swimming to one spot or another, and that gives us some control over what we’ll encounter. But in real life we can usually do much more than that; we can reshape the things themselves that we interact with. Rivers are rather resistant to such efforts when we’re alone in the middle of them.