Quantum Copenhagenists will tell you if there is a stop sign, it only manifests itself by the act of observation. When no one is looking, there is nothing there. This is like the cognitive process of a baby before learning object constancy. But if nothing is there, how does the stop sign know how to appear at the same spot when observed later? Why can't we look, see a red stop sign, look away, look again and see a green stop sign, look away, see the stop sign has moved, look away and look and find the stop sign has gone? Copenhagenists will tell you it is the mind of the observer which keeps track.
What about change blindness then? Huge changes in perception can be made without being noticed if the observer looks away for a while. The mind does not always keep track of such things. But if it doesn't consciously register, maybe such changes are going on all the time? How can we tell? Only when the location of the stop sign is registered in short term memory can we notice that it has changed. Might we as well claim we create reality according to our beliefs? When something is registered in short term memory, the mind keeps track and manifests according to its subjective beliefs. If it is not registered? Might the laws of physics only hold when we keep note, and be blatantly violated when we don't notice? Can we have glitches where we see a black cat cross our path from one side to another, and then see the same black cat cross again from the same initial direction without seeing it walk back, but only if we never registered the first crossing in our memory in the first place?