This is based on the Hugh Everetts interpretation of quantum mechanics, where the waveform never collapses but the observer becomes a part of it, thus experiencing decoherence of the wave form from their point of view. So, let's say someone is doing the two-slit experiment. The particles going through the two slits are in a state of quantum superposition. But now an observer comes along. In order to observe the particles of the experiment, the observer must interact with them in some way - say photons bounce off those particles and then hit a camera, the particles in the camera interact with other particles along electrical wires and end up producing an image on a screen, photons bounce off the screen and hit the observer's eyes. With each interaction, the particles involved in the interaction become part of the quantum superposition, i.e., part of the experiment's waveform. The observer is also part of the waveform. This is why the observer doesn't see any superposition; they only see each particle go through only one of the two slits. Instead of a single observer seeing one particle in superposition between both slits, different versions of the observer (these different versions are now part of the quantum superposition) each observe a different, single, particle position, and are not aware of any alternatives. My question is this: if that is how decoherence works, then why does an unobserved two slit experiment result in an interference pattern? Shouldn't observing the interference pattern involve the observer in the waveform too, so that they end up just seeing a normal pattern from each particle going through only one slit? The interference pattern was formed by the experiment and therefore is part of its waveform, and photons interact with the pattern and then hit the observer's eyes, thus involving them in the waveform just as if they had watched the experiment. There must be something wrong with my understanding of decoherence. Thank you to anyone who can help me clear it up! Apologies if my explanation was confusing, please feel free to ask me to clarify anything.