The observer, unless I'm mistaken, will always remain "uknown". At least in our physical state, we will never know what is seeing what we're seeing. All we know is what "passes the information along", light, eyes, cameras, brain, etc. however, we don't know where all that information is going. How could we ever truly know? And everyone is like that.
So, what if it goes to the quantum level, and beyond? I mean, where YOU reside not in a room as a human body, but at something that could be beyond the quantum level. Not even beyond, it could be anything. No one knows where we truly reside. The information is just coming to us. It helps I think to just think of it - where are you? What are you? Its a huge mystery, probably the biggest mystery. If you just keep thinking about it, or as the C's sometimes say, meditate on it, focus on it, the reality of it strikes harder and harder, until the quality of what you are sensing changes, a persective shift. I just think its important to get a handle on what the observer is, personally I don't think we will find it in a brain, or in an eye, etc. I think it is literally us - but I don't really think that its an observer which changes things like what happen in the double slit - I think its more likely the "filters" which exist in front of the path of observation which cause this.
I think the double slit experiment and the conundrum it presents is down to filters, or, "gaps" of missing information. For example, our eyes don't see certain light, and simply can't see it, ever, until its translated/converted into the light that we can see, or into audiable form. I guess this is what scientists are trying to do - convert the quantum world into a non-quantum way of understanding. Seeing "infrared" by representing it with colours in the visible range, so to speak.
I say filters because if you are in a room made out of glass which blocks the colour yellow, you may see people lifting up seemingly invisible boxes if they're lifting up yellow ones. But I think the filter is a lot more complex, and it is our minds.
It think its possible that our minds, as the "basis filter", are like an ongoing project through the densities. The more we work on our minds, the more it changes to allow more to pass through in an unedited form, and also "bandwidth" can be increased, as well as archetypal/symbolic information which has "infinite" application. I suppose its kind of like a rubicks cube, or any other puzzle? What I am saying is its possible the mind in the state its in for us, currently, is like a "selector", or "resonator", and is fine with seeing an interference pattern or not, but can't "select" more than one path (like your PC monitor is never going to play music out of its pixels). Afterall, we experience the non-quantum world, and if we were as the C's say, in 1st and 2nd density, they are also, to the best of my understanding, not quantum. Which means we never had to consider it, never had much of a use of it for survival, or had any interest in it, so we just aren't "tooled up" for it. To me that makes a lot of sense - we're just "meeting" it for the first time, right now.
So my premise is that the interference pattern is the reality, and the non-interference pattern is the filtered reality.
This way, the mind would fill in the gaps automatically. If we observe the particle, the mind's assumption - its "hypnotism" in a way, its "denial" - or simply the fact that it cannot see more than one particle because its looking at the quantum world from a non-quantum perspective, using a "non-quantum tool", could create the non-interference pattern, because it just can't accept the interference pattern after having seen the single particle. But when the mind doesn't see the single particle, its freed of some "shackles". It can accept, seeing as it hasn't SEEN a single partcile, that "somehow" the particles exist all at the same moment, and perhaps secretly believe, or hope, that there is some non-quantum, linear explanation - at least, it leaves the possibilty open, so that the truth it CAN accept can come through.
I don't think my little hypothesis isn't new, but I haven't seen it before, and its hard to look for, it would be interesting to know if anyone has some more info about it. Mostly I see things where people say the particles are making decisions, which strikes me as a bit of a joke, so I don't take it very seriously. But thats what they always seem to suggest in the lamen explanations.