As a child, I was visited by an alien. I remember the sensation of not being able to move or speak and seeing this other-worldly face. Some time later, when I saw a documentary about people who had been visited by aliens, I felt a chill of recognition. Their experiences matched my own.

People all over the world describe the appearance of aliens in a similar way, and this is often cited as proof that they are among us. I think that there is a different and more plausible explanation for the universality of this phenomena.

The alien image above was generated automatically from a collection of human faces. How was that done? Basically, I train some “neurons” to capture as much information about human faces as possible. These neurons try to split up the work in an optimal way, and robustly we see a neuron that represents the alien face. When you add this together with a few other informative facial features, you can flexibly recognize many types of faces. Seeing this pattern causes a strong sense of recognition because it activates core features in our facial recognition circuitry. However, having this neuron fire by itself is unnatural – no human face would cause just this one pattern to fire without any accompanying ones. Therefore it also strikes us as alien.

Dreams and drugs cause random firing patterns that sometimes activate unusual combinations of our facial recognition circuitry. The universality of people’s perceptions of alien faces only reflects the universal principles underlying the circuits in our head. Now we just have to reconstruct these principles: the truth is out there (in here?).