Ed. Note: Some of the content of this blog appeared previously in the "Illusions" column that we write for Scientific American Mind. 


Inside your brain, you create a simulation of the world that may or may not match the real thing. “Illusions” are the phenomena where your perception differs from physical reality in a way that is readily evident. You may see something that is not there, or fail to see something that is there, or see something differently from the way it actually is.

Such illusions offer a window into how our neural circuits create our first person experience of the world. The simulated reality your brain creates—which some call consciousness—becomes the universe in which you live. It is the only thing you have ever perceived. Your brain uses incomplete and flawed information to build this mental model and relies on quirky neural algorithms to often—but not always—alleviate those flaws.

But what if there was no way to differentiate simulation from reality?

In the movie The Matrix, Morpheus asks Neo: “What is real? How do you define real? If you’re talking about what you can feel, what you can smell, what you can taste and see, then real is simply electrical signals interpreted by your brain.” What the movie doesn’t tell us is that even when Neo accepts the red pill and awakens from the fake world of the “matrix” into the “real world,” his brain will continue to construct his subjective experience, as all our brains do. Neo will continue to live in the biological Matrix of his own mind.

Yesterday, the journal Nature published a short science fiction story that I wrote to explore the concept that we create reality in our own brains, irrespective of what the world outside may be like. It’s titled “Age progression,” and you can read it here. Hope you’ll enjoy it!