- If a tree falls in the forest and nobody is there to hear it, it really does not make a sound. What you experience as sound is constructed in your brain.
- You cannot experience the world, or even your own body, objectively.
- By seeking out new experiences, your brain teaches itself to craft new meaning.
Signals from the environment, such as those detected by your sense organs, have no inherent psychological meaning. Your brain creates the meaning.
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This year’s World Chess qualifying tournament brought a new twist: the heart rates of the players were broadcast live, with the help of AI software, so viewers could (supposedly) gain insight into the players’ emotions during a match. But can emotions be detected from mere heartbeats? When your own heart pounds wildly in your chest like a sledgehammer, does it necessarily mean you’re frightened? Angry? Excited? Full of joy? What if you’ve just finished a strenuous workout or knocked back a bit too much espresso?
When it comes to the question of what your heart rate means, psychologically speaking, the scientifically correct answer is: it depends. That’s because physical signals from within your body have no inherent psychological meaning. A particular heart rate does not indicate any particular emotional state. It’s not the case, say, that 100 beats per minute is happiness and 150 beats per minute is anger. The pounding in your chest during instances of both emotions can be physically identical. More specifically, your heart rate may vary just as much among different instances of anger as it does between instances of anger and happiness. Ditto for every spurt of cortisol, every trickle of dopamine, and every other electrical or chemical change in your body. What differs is the meaning that your brain makes of the physical signals in a particular context.
Physical signals have no inherent psychological meaning
The same is true of physical signals from the outside world. When a tree falls in the forest and slams into the ground but no one is present, it does not make a sound. It does produce a change in air pressure. That change becomes meaningful to you as a sound only when it reaches sensory surfaces inside your ear (your cochlea), producing a different physical signal that travels to your brain, where it meets an ensemble of other signals that represent your knowledge of falling trees and what they sound like. You don’t hear with your ears; you hear with your brain. If that same change in air pressure encounters your rib cage rather than your cochlea, you may feel a thudding in your chest rather than hear a sound.
Light waves similarly exist in the physical world, whether or not a human is present. But “color” is a feature constructed as your brain weaves those signals together with others of its own creation. So a statement like, “The rose is red,” is more precisely stated as, “I experience the wavelengths of light reflecting from the rose as red.” The redness isn’t in the rose. The light waves detected by the sensory surface in your eye (your retina) modulate signals along the optic nerve that encounter other signals in your brain that reassemble past experiences and give those incoming signals psychological meaning — and voila, you experience the rose as scarlet, ruby, or some other variety of red.
The model inside your brain
Your brain constantly runs a model of your body as it moves through the world. You come to know that world only through your cochlea, retina, and the other sensory surfaces of your body. Their signals, along with those streaming from within your body, continuously confirm or correct the ongoing signals in your brain. The implication is a bit startling: You cannot experience the world, or even your own body, objectively. Your experience is always from a particular perspective, and no perspective is universal.
Your brain’s internal model is formed from ensembles of sensory signals from your past, sourced from the body it is attached to, the world that surrounded it, and the other people who curated and inhabited that world. Their words and actions wired your brain with the concepts of your culture, empowering your brain to see red in a rose, hear trees fall, and understand your racing heart as joy in one situation and sorrow in another.
This idea, called relational meaning, is familiar in quantum physics. As Carlo Rovelli beautifully explains in his latest book Helgoland, nature is not filled with permanent objects but with relations between quantities. When an electron is not interacting with anything, it has no physical properties…