Individual photons behave the same way. As in, if you fire quantized packets of light at the double-slit apparatus, one at a time, they will statistically match what happens in bulk.

It's so not-magic, photons will not only do it in the absence of a human observer, they'll do it in the absence of other photons. We talk about waves and particles - but these are abstractions on the scale of our ancestral environment. The actual rules are downright wacky in a way we have a hard time reasoning about.

And that's before shit like chromodynamics, which still sounds like something I made up.