In searching for “what percent of the light spectrum can humans see” I found answers varying from 0% to a maximum of 2.3%, depending on your definition of “light spectrum,” whether you’re asking in terms of a linear scale or a logarithmic scale, and whether you’re using wavelength or frequency  .
Painfully slow frame rate
The problem doesn’t stop there, however. Searching for “frame rate of human eye” suggests and upper bound of 60 fps.
When someone drops a piece of gelatin, is this what you see?
Dark matter + Dark energy
The above image is a screenshot of the universe’s virtual machine as it existed approximately 13.7 billion years ago. From it, we learned that:
It also constrained the content of the present-day universe; 4.6% atoms, 23% dark matter and 72% dark energy.
That means that everything you learned in school about the world, and everything our scientific instruments can see, only deals with just 4.6% of the universe. And that’s just what our scientific instruments can directly see. Of that, we only see a fraction (0% to 2.3%) with the naked eye, and only at about 60 frames per second (when you’re really paying attention).
Conclusion: don’t make fun of schizophrenics
Perhaps they can simply see more of the universe than you can.