Other Minds: The Octopus and the Evolution of Intelligent Life

by Peter Godfrey-Smith

In 1950, the German physiologists Erich von Holst and Horst Mittelstaedt introduced a framework for talking about these relationships. I used one of their terms earlier in this chapter: efference copy. I’ll now outline some more of their framework. They used the term afference to refer to everything you take in through the senses. Some of what comes in is due to changes in the objects around you – that is exafference (with “ex” for outside, and pronounced in the same sort of way as “ex-boyfriend”) – and some of what comes in is due to your own actions: that is reafference (pronounced “re-afference”). Animals face the challenge of distinguishing between the two. Reafference makes perception more ambiguous. If your own actions did not alter what your senses pick up, life would be easier in some ways. One way to deal with the problem is with the “efference copy” mechanisms I described earlier. As you move, you send a signal to the parts of yourself that deal with perception, telling them to ignore some of what comes in: “Don’t worry, that’s just me.” Problems stem from reafference, but so do opportunities. You can affect your own senses in useful ways. Here the aim is not to filter out an unwanted contribution to what is perceived, but instead to use your actions to feed perception. A simple example is writing something down, a note to yourself, which you will read later. You act now, changing the environment, and later you will perceive the results of your act. This will ena...