The Brain IS A Bayesian Net

I've occasionally rambled that there's a big difference between our basic, everyday sort of reasoning (e.g., How far do I need to lift this spoon ? How hard should I push on this door ?) and our higher reasoning (e.g. Is this galaxy experiencing ram pressure stripping ? Is Nigel Farage actually a demonic toad or is that just me ?). I've noted that our everyday reasoning appears to be generally extremely sensible - unless something goes catastrophically wrong, I can get the spoon in my mouth and not my eye; I can push the door open and not have to struggle. Those sorts of thought processes appear to be difficult to fool - they nearly always get things right, apparently in a very evidenced-based, logical way.

In contrast derailing higher reasoning appears to be easy. Only only has to whisper "politics" and everything collapses into a heap and spontaneously ignites.

I suppose it could be that our everyday, unconscious thoughts are rarely affected by emotions and other irrational factors. They're not immune to such influences (optical illusions being perhaps the best example), but they require rather contrived circumstances compared to what we generally encounter. It doesn't seem that your mood strongly affects what you actually see, though it certainly does affect how you interpret it.

You might also remember this post ("Your brain is NOT a Bayesian net"). It seems to me that the article below presents a nice contrast. As far as higher reasoning goes, the brain does a crappy job of considering everything it knows all at once. It seems strongly influenced by emotion and short-term memory. It definitely does not stop to consider all its accumulated knowledge and do a detailed comparison - it couldn't, because then we'd be stuck for six weeks every time we wanted to put on a new pair of socks. The best example is probably this :

So the brain is fooled by what it has to hand. It certainly can do highly complex, rational analysis, but that requires a conscious, deliberate effort. That's perhaps what consciousness is for.

In contrast the article below suggests that the brain's reasoning is much more Bayesian :

In this new study, Jazayeri and his team wanted to understand how the brain encodes prior beliefs, and put those beliefs to use in the control of behavior. To that end, the researchers trained animals to reproduce a time interval, using a task called "ready-set-go." In this task, animals measure the time between two flashes of light ("ready" and "set") and then generate a "go" signal by making a delayed response after the same amount of time has elapsed. 

They trained the animals to perform this task in two contexts. In the "Short" scenario, intervals varied between 480 and 800 milliseconds, and in the "Long" context, intervals were between 800 and 1,200 milliseconds. At the beginning of the task, the animals were given the information about the context (via a visual cue), and therefore knew to expect intervals from either the shorter or longer range. 

Jazayeri had previously shown that humans performing this task tend to bias their responses toward the middle of the range. Here, they found that animals do the same. For example, if animals believed the interval would be short, and were given an interval of 800 milliseconds, the interval they produced was a little shorter than 800 milliseconds. Conversely, if they believed it would be longer, and were given the same 800-millisecond interval, they produced an interval a bit longer than 800 milliseconds.

But this is just dealing with one task with very limited, immediate prior knowledge. It would be interesting to see how many sources of prior information both humans and animals are able to incorporate into a decision, and for how long this lasts. I suspect the Bayesian thing will be limited both in time and extent. I doubt there will be much direct applicability to what we believe in the stronger sense of the word, as opposed to what we currently suspect or happen to think. We might higher-reason in Bayesian-network fashion, but it will certainly be over a limited range of information and unfairly prioritise the recent. Or much more, wholly irrational factors may be decisive. It's interesting either way.

Neuroscientists find brain activity patterns that encode our beliefs

For decades, research has shown that our perception of the world is influenced by our expectations. These expectations, also called "prior beliefs," help us make sense of what we are perceiving in the present, based on similar ...