Double slit experiment with animals as observers

Question

I was searching about the double slit experiment, reading and watching videos, etc.

If I understood correctly, when they measure the photon it behaves like a particle.

On the Youtube video Tom Campbell: The Key to Understanding Our Reality, the speaker says that during one of the double slit experiments they let the detector on but did not store the measurement data and so the photon behaved as a wave; only when they stored the data did it behave as a particle. This would mean that the measurement could later be seen by a human and so the photon behaviour would be associated with human consciousness.

Now, what would happen if you let the detector on and let an animal, like a cat or dog, see the measurements? Would the photon behave like a wave or a particle? Only the animal would be able to see the measurements and it would not be stored in any way that a human can have access to.

If the photon behaves like a particle, would this mean the animal is conscious like a human?

If not, would this mean that only humans are concious and can interfere with the photon?

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N.B. The information provided in the YouTube video is wrong. Please see correct answer below.

Answer 1

The claim that

during the experiment they let the detector on but did not stored the data so it showed waves, only when they stored the data it showed as particle.

is inaccurate and inconsistent with quantum mechanics. In a double-slit experiment, any device that can even in principle provide which-way information will destroy the interference patterns. This is independent of whether you record the data provided by that device or not.

More specifically, Campbell's claims between 8:00 and 10:30 on the linked video are flat-out incorrect. No such experiment has been performed, and I would advise viewers of that video to find better learning resources.

A reliable, reproducible experiment where switching off and on the which-way data recording device triggered a change from 'particle-like' to 'wave-like' interference behaviour would be of the utmost interest and essentially warrant a Nobel prize. If and when someone performs such an experiment - trust me, you'll hear about it.

Answer 2

If it behave like a particle would this means the animal is conscious like a human?

No, it would simply mean that animal's sensing systems and interaction with the photon is well modelled by a quantum observable.

You may not have met this word before; in short, an observable is a mathematical model for the measurement itself: it is a operator that acts on quantum states together with a special recipe for working out how its action bears on experimental outcomes.

Now this all sounds like very circular reasoning and it is. But the notion of a conscious system is a way too hopelessly complicated thing for us physicists to grapple with intellectually. So one approach is to abstract out of such a thing the essential behaviors that we observe to observe common to all quantum measurement experiments and make a mathematical description of these essentials called the observable. We then define a "measurement" to be anything that invokes the recipe of the observable on the quantum state. That way, we can avoid being bogged down and utterly defeated by indescribable notions such as a conscious system (which itself is likely to be a quantum system comprising Avogadro sized numbers of quantum particles).

Another approach is to probe more deeply the measurement itself and work out what really happens to invoke the mathematical model of the observable. But this is the famous quantum measurement problem and it is still one of the biggest open questions in all of science.