# Does consciousness cause Wave-Function collapse?

1. Apr 1, 2015

### HiggsBoson1

I was wondering if consciousness really causes the wave-function to collapse, and if this is the reason why our behavior is not erratic. Thanks!

2. Apr 1, 2015

### StevieTNZ

There is, as far as I am aware, no consensus of the solution to the measurement problem of Quantum Mechanics. So consciousness may cause collapse of the wave function, or it may not.

3. Apr 1, 2015

### rootone

Consciousness causing the wave-function to collapse isn't a very popular idea these days and there are alternative explanations, though as far as I know there isn't any evidence that it is involved or if it isn't.
The wave function collapse happens regardless of whether a human or any conscious being is present, all that is needed is something does an observation.

Imagine a scenario where a QM experiment is done, and the result is recorded by machines and stored as a data file.
Let 100 years pass then distribute copies of the file to a million people.
They will all see the same thing

4. Apr 1, 2015

### atyy

Is there any interpretation in which consciousness is not somehow involved in wave function collapse?

Edit: I guess collapse is real in GRW and CSL. But couldn't it be said that consciousness is involved in wave function collapse in Copenhagen, Bohmian Mechanics and Many-Worlds?

5. Apr 1, 2015

### StevieTNZ

That doesn't disprove consciousness causing collapse.

6. Apr 1, 2015

### StevieTNZ

I'm not really sure. I agree with your comments about GRW etc.

7. Apr 1, 2015

### rootone

But it does prove that the outcome isn't dependent on a human being there when the experiment took place,
and also what I consider to be the most ridiculous variation on that theme-
which is that different (human) observers being present at the time the experiment was done might produce different results.
It's pop-sci stuff, I know that, but still many seem to believe that's the idea.

Last edited: Apr 1, 2015
8. Apr 1, 2015

### craigi

CI is deliberately agnostic.
BM has no observer role.
MWI has observer selection. Don't try this at home, but see quantum suicide.

9. Apr 1, 2015

### bhobba

MWI has nothing to do with 'observer selection'. Given the mixed state ∑pi |bi><bi| after decoherence, which is observer independent, each |b><bi| is interpreted as a world and everything just keeps on evolving.

Thanks
Bill

10. Apr 1, 2015

### atyy

But there is no perfect decoherence, so there is no after decoherence. In Wallace's accounts he tends to refer to some sort of coarse-graining. So this seems to assume that there is an observer who is doing the coarse-graining? Or to put it another way, each observer within MWI can use Copenhagen, including collapse. So to derive that, do we need an observer?

This isn't a particularly quantum argument, since BM and MWI are essentially classical in ontology. For example, to derive Newtonian mechanics as a good approximation to GR, do we need an observer in order to define a "good approximation"?

11. Apr 1, 2015

### bhobba

This conciousness causes collapse stuff is, IMHO, silly in the extreme. It faces severe problems. But they can be overcome - a coherent (but very very weird) view of the world can be formed.

Here we face what science is about. Science is about TRUTH. But truth discovered by correspondence with experiment. Experiment is always the final arbiter. It just may be that one day we can prove that conciousness causes collapse. It cant be ruled out.

Its like solipsism - nearly everyone rejects it as being silly - which it is - I certainly laughed my head of when I heard about it and thought how could anyone be gullible enough to believe such obvious rot. But science, correctly, has a different standard - rot it may be - but if experiment shows it is true rot we must accept it. Isaac Asimov expressed it this way. Religious cults, like for example Scientology, say 2+2 = 5 and make no mistake about it, science says almost certainly 2+2 = 4, but we need constantly to check it.

You will find once you integrate this into your world view many things become a lot clearer including the shenanigans of politicians - but that is for you to discover.

Thanks
Bill

12. Apr 1, 2015

### bhobba

Of course there isn't. But it makes no difference because in all situations in practice it is below detectability very very quickly. You cant ever detect those other worlds. It is generally thought detectability in this case is inherent ie is not technologically dependant ie is way below any level of current or future technology's ability to detect - but one never knows does one - that is the very essence of science.

Now if you want to attack MW I think the quantum eraser experiment may prove difficult to handle - what happens to those worlds when decoherence is unscrambled? I don't know the answer to that one in that interpretation - I will leave it up to those expert in it.

Thanks
Bill

13. Apr 1, 2015

### atyy

I wasn't trying to attack MWI. I'm mainly trying to understand Zurek's statement in http://arxiv.org/abs/1412.5206: "Quantum Darwinism shows why only such redundantly recorded pointer states are accessible to observers|it can account for perception of quantum jumps'. However, full account of collapse involves consciousness', and may have go beyond just mathematics or physics. "

Although he mentions collapse, I think he is operating within his "existential interpretation", which as far as I can tell is a version of MWI, and he is trying to explain why although there is no collapse in the full interpretation, individual observers experience or use collapse.

14. Apr 1, 2015

### craigi

Which of those worlds you find yourself in is subject to an observation selection effect under the MWI.

Quantum erasers present no problem for the MWI since, as you already pointed out, the split into different worlds occurs at decoherence.

Last edited: Apr 1, 2015
15. Apr 1, 2015

### bhobba

Nope - its subject to the Born rule which MW adherents think can be derived from decision theory. I have gone though it from Wallice's book and believe there is a tacit assumption of basis independence which is the assumption of Gleason.

Just as background for others an observation selection effect is a concept from statistics that say you want to survey spending habits and you drop of a questionnaire to households in English. You have prior selected only those that can read and write in English. In MW there is noting analogous to that - the world the outcome occurs in is determined by the Born rule - you being there or not has nothing to do with it.

Thanks
Bill

Last edited: Apr 1, 2015
16. Apr 1, 2015

### craigi

The Born rule of course applies, to outcome prediction. However testing predictions is subject to observation selection bias. Ignoring it leads to invalid conclusions.

17. Apr 2, 2015

### carllooper

The example of 2+2=4 vs 2+2=5 is not a very good example, because such can be resolved by reference to the definition of what those employed terms mean. There's no need to perform any check on 2+2=4 (or 2+2=5) because one is so by definition, and the other is not. In other words, the definition rules out, in advance, any counter-proposition (and any need to perform any check). Certainly we can arrange 2 pairs of apples on a table, and count them up, but do we really need to do that? For it wouldn't be any different if we'd used oranges, or pears. We otherwise risk suggesting there might be a difference were different fruit used in such a check. But we already know there wouldn't be, because 2+2=4 does not depend on any fruit in the first place. Mathematics can be elaborated without any need to check anything outside mathematical errors.

Rather, what we mean by checking something in science is a lot more involved than simply checking for simple mathematical errors (or not so simple in many cases) but checking to what extent a particular mathematical expression models an observation. If it's a mathematical model (as most are) it will already be internally consistent (because otherwise it wouldn't be a mathematical model) but it may not be externally consistent. For example, Newton's mathematical model of gravity is internally consistent (without any mathematical error), but that doesn't guarantee (as we subsequently discovered) that it was entirely consistent with observations of gravity. The model turned out to be an approximation (even if an extremely good one).

Certainly we need to check models against internal inconsistencies, but the more important task (and not so easily done by thought alone) is checking what models claim in relation to observations. Some models, of course, don't make any claim in relation to any observations so they only need to be checked for consistency.

On a point of order, I have no interest in Scientology (or any other religion), but do Scientologists really say that 2+2 = 5? Or is that more of a metaphorical claim?

C

What did the string theorist say to her husband when he caught her with another man?
"Wait", she said, "I can explain everything".

Last edited: Apr 2, 2015
18. Apr 2, 2015

### atyy

It doesn't matter whether consciousness causes the wave function to collapse or not in order to answer the second question. By continuously observing an object, the object's behaviour can be frozen or erratic. Obviously in everyday life, things are not frozen and things are not hugely erratic. So the answer is that by picking the right observable in the formalism of continuous observation, quantum mechanics is, at least heuristically, to reproduce the classical world we see. This emergence of classical dynamics as a good approximation has been worked out in a few cases, eg. http://arxiv.org/abs/quant-ph/0211036, http://arxiv.org/abs/1104.0820.

19. Apr 2, 2015

### carllooper

Regarding consciousness causing wave function collapse - this assumes, apart from anything else, that wave functions undergo collapse. When "wave function collapse" was first proposed it wasn't proposed as some sort of scientific theory, but as a kind of interpretational crutch that one could lean on, until one better understood the underlying logic. I don't recall who, but in the early conferences someone voiced an objection to the concept of collapse - the response to which was that if they were understanding the theory in the first place they wouldn't need such a crutch (and therefore wouldn't be complaining about such).

Nevertheless, ever since, this crutch has been recast as some sort of "problem" in search of a solution, one of which is the idea of consciousness causing such. But in any case lets assume "collapse" does occur (or the term "collapse" otherwise refers to that which does occur) well it should be obvious that it doesn't require consciousness insofar as a photographic plate can register such collapses without having any consciousness. Unless, of course, we assign consciousness to a photographic plate (and why not I guess).

More relevant is the question as to what such a theory (for want of a better description) might tells us. And in short it doesn't tell us much of anything at all. Even if consciousness did cause collapse (and photographic plates were examples of consciousness) in what way could we exploit such a theory? The answer to that question will tell us if we're moving closer towards understanding the physics or moving further away instead - into some other disciplinary bracket. As far as I can tell, it moves us into theories of consciousness rather than theories of physics.

A more difficult question is how to understand the model without such a crutch. I'm not sure I do. I still need the crutch from time to time. But I'm happy enough using it - it works for me.

One thing I know is that the issue of individual particle detections doesn't play a very big role in most situations. A wave function can be used to describe the "truth" behind an observation but it can also be used to describe an observation without requiring a collapse of the wave function. For example, it can be used to describe the distribution (or density) of particle detections in an experiment. While it can't describe any particular detection (in terms of it's exact position in space on the photographic plate) it turns out this is not a severe short coming. The aggregate pattern is not a function of individual detections but a function of the function so to speak. The impertinence of each particle, in assuming a position it couldn't possibly assume, is tempered by their sheer undying conformity to the square of the wave function (or wave functions plural as Bohr would prefer). This more than makes up for any madness any detection on it's own might inspire.

C

Last edited: Apr 2, 2015
20. Apr 2, 2015

### craigi

It is the lack of any evidence for any mechanism for wavefunction collapse that leads to the MWI. If such a mechanism did exist then there would be no need for the MWI.

The CI was unable to find a definition of an observer, conscious or otherwise, to collapse the wavefunction. The simplest solution, to me at least, is that no such collapse actually takes place.

Last edited: Apr 2, 2015
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