[ExI] Subjective/Objective

[Ben Zaiboc]

On 08/07/2026 04:14, Brent Allsop wrote:
> You realize, right, that the left half of your brain knows what it is like for the right.


I think you have an inaccurate view of what the corpus callosum is for, and what it actually does.

All that's happening is that various parts of the two halves of our brains are passing messages to each other, as and when necessary. It's not about synchronising the two hemispheres so that exactly the same thing is happening in each, that would be silly.

If the left side of your brain 'knew what it is like' for the right side, they would both be exactly the same, and there would be no need for two sides. At least one reason for our brains being organised into two similar parts is that each part deals with signals relating to one side of the body. Because things don't happen symmetrically to and with our bodies, the same is true with the two hemispheres. Different things are going on in each part of the brain. Messages pass between them when it's necessary for co-ordination, that's all.

Two people can co-ordinate their actions, in various sports for example, without having to know what each other is thinking. The hemispheres of the brain do this as well.

Think about when you pat your head and rub your belly (assuming you can do this. I know some people can't*), or play a musical instrument, or anything else where your two hands are simultaneously doing different things.

If the two hemispheres were synchronised, these kinds of actions wouldn't be possible. The hemispheres need to be co-ordinated, not synchronised, so different things are going on in each, but they co-operate to get a complex task involving both sides of the body, done.
A similar thing happens with sensory input. We need to co-ordinate information from the two halves of each eye, or from the two ears, etc.

So no, the left half of your brain does /not/ 'know what it is like' for the right. Stick a pin into your left leg but not your right, and you'll see that it's true.

-- 
Ben

* In fact, I wouldn't be surprised if the inability to pat your head and rub your belly simultaneously is because the two halves of your motor cortex are trying to synchronise instead of co-ordinate. A little bit of practice can soon sort it out, though, because that's exactly the kind of thing the corpus callosum is for. People who can't do this are like people who can't speak french. They just haven't practiced enough.