Daniel Yon has an interesting piece at Aeon on how our brains predict the outcomes of our actions, shaping reality into what we expect, and why we see what we believe, rather than the other way around.
This idea is part of a growing sentiment in the cognitive science community that prediction is at the heart of what brains bring to the picture. The thing to understand is that this isn’t about conscious prediction (although that’s part of it) but about pre-conscious predictions that enter into our awareness as perceptions. Put another way, perceptions are predictions.
This can be a little clearer if we back up from an evolutionary perspective and consider the nervous system of an early chordate worm. Such a creature has a nodocord, a central nerve running along its length, where its sensory data is integrated and which serves as a central pattern generator, its main source of motor action.
This creature endogenously generates rhythmic movement and responds to stimuli with fixed action patterns, meaning that its behavior is largely set by its genetics. Although it’s capable of some classical conditioning, its genetic programming doesn’t provide much flexibility.
In time, the creature’s descendants will develop sensory apparatus to do things like detect light, vibrations, and low concentrations of chemicals. What will these capabilities provide to those descendants that the early creature lacks? We can’t reference their eventual evolution into sight, hearing, and smell, because natural selection doesn’t act with foresight. Every mutation has to be adaptive if it’s going to propagate and be enhanced.
The answer is prediction. Initially these predictions were very simple. Sensory data simply provided earlier triggering of reflexes that might previously not have been triggered until the organism came into direct contact with the stimulus. The early reactions provided a survival advantage. But over time, as the sensory data increased in resolution, the predictions became more detailed, until we get a fish that can see and flee from a predator before the predator has a chance to bite into it.
As we follow evolutionary history, the predictions become progressively more sophisticated, until we arrive at us predicting not only our spatial and temporal environment, but social situations, as well as our own actions.
As Yon describes in his article, perception being prediction means that sometimes we mis-perceive, that is, we predict wrong. Being that the prediction is pre-conscious, it often isn’t something we can guard against. We can only be sensitive to the error signal when it arrives. Put another way, people’s worldview has a powerful effect on what they perceive.
This is one of the reasons why all observation in science is theory laden. We can attempt to make pre-theory observations, as some philosophers have urged, but ultimately our perceptions come to us embedded in our existing beliefs. All we can do is see how accurate, or not, our predictions are, and be open to revising our beliefs when those predictions fail.
I think the prediction paradigm has a lot of power, although I do sometimes worry that maybe it’s getting overused to describe everything about the brain. The question is, are there counter-examples out there? Or any other data that can’t fit into it? Is the brain basically reflexes plus predictions?