"Has anyone, including and especially the claimant, gone out of the way to disprove the claim, or has only confirmatory evidence been sought?"
Believe it or not, I have spent quite some time thinking about how this theory/explanation might be falsified. A true test of falsification would require more concrete predictions about the effects of and interactions between multiple observers of the same outcome. To that end, I am particularly interested in people and situations where someone besides me may be the 'strongest observer'.
One way to find an observer who is likely to have more of an effect on the outcome than I will is to find a situation where the other party has more of an emotional investment in the outcome. I wouldn't attempt to induce any situation where another person might be traumatized (informed consent would taint the experiment anyway), so mostly I take what I can gather from existing situations. And sometimes card and board games get a little out of hand when people think they can best me at 'picking the universe'. ;)
Today provided an excellent situation for study. Two observers (call us N and O) in a situation where O has spent a lot of time thinking about a particular outcome (call it P). O has very specific expectations that lead him to think the outcome will be P1 and not P2 (dichotomous split). O also has a lot of emotions invested in the outcome and claims to want P1. (O tells this all to N, so N isn't guessing at what O is thinking.) N agrees that P1 would be the preferable outcome. N agrees that P1 is the likely outcome based on classical knowledge of the situation, but N (knowing how these things go) suspects that O, as the strongest (or only) observer of the critical moment of observation, would likely find himself in the universe where he experiences P2.
N agrees to be present at the critical window of observation. (The critical window of observation is all observations made at a specific place during the period of time that define the 'event'.) Now we have N and O as the only two observers of significance for the event/outcome P. N can consciously make an effort to steer both N and O towards outcome P1. O is a wild mess of chaotic thought and emotion that is likely to pull them both towards P2. As the end of the critical time window approaches, N feels safe enough in the outcome (P1) to depart from the critical observational space in order to answer the call of nature.
No doubt you can guess what happened. By the time N returned to the scene, the outcome was irreversibly P2. N wants to say to O "What? You couldn't hold that universe for two minutes without me?" but doesn't.
And now N gets to speculate about multiple observer dynamics. :) N has sympathy for the original creators of Observational Theory who must have had one helluva time trying to deal with summing together all the possible forces that contribute to an outcome. The truly disturbing question is - What, if any, elements of N's decision to momentarily leave the scene can be attributed to O's pull towards the ultimate outcome P2?
