Perceiver-independent phenomena

Chapter 7 endnote 4, from How Emotions are Made: The Secret Life of the Brain by Lisa Feldman Barrett.
Some context is:

[Molecules, atoms, quarks, Higgs bosons, etc.] are supposed to exist in the natural world whether or not humans are present ​— ​that is, they are thought to be perceiver-independent categories. [...] Philosophers call them “ontologically objective.”

Technically speaking, the ability to perceive these particles is not perceiver-independent. As Einstein once famously wrote, "Physical concepts are free creations of the human mind, and are not, however it may seem, uniquely determined by the external world.”