Daryl Bem's Presentiment Experiments

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Re: Daryl Bem's Presentiment Experiments

#61  Postby Thommo » Dec 13, 2010 12:29 am

Gosh, this is an interesting thread that I've somehow overlooked for months.

I particularly enjoyed reading http://dl.dropbox.com/u/1018886/Bem6.pdf

This excerpt from p5 is particularly illustrative:-

To appreciate how unlikely the existence of psi really is, consider the facts that (a) casinos make profit, and (b) casinos feature the game of French roulette. French roulette features 37 numbers, 18 colored black, 18 colored red, and the special number 0. The situation we consider here is where gamblers bet on the color indicated by the roulette ball. Betting on the wrong color results in a loss of your stake, and betting on the right color will double your stake. Because of the special number 0, the house holds a small advantage over the gambler; the probability of the house winning
is 19=37. Consider now the possibility that the gambler could use psi to bet on the color that will shortly come up, that is, the color that will bring great wealth in the immediate future. In this context, even small effects of psi result in substantial payoffs. For instance, suppose a player with psi can anticipate the correct color in 53.1% of cases—the mean percentage correct across participants for the erotic pictures in Bem’s Experiment 1. Assume that this psi-player starts with only 100 euros, and bets 10 euro every time. The gambling stops whenever the psi-player is out of money (in which case the casino wins) or the psi-player has accumulated one million euros. After accounting for the house advantage, what is the probability that the psi-player will win one million euros? This probability, easily calculated from random walk theory (e.g., Feller, 1970, 1971) equals 48.6%. This means that, in this case, the expected profit for a psychic’s night out at the casino equals $485,900. If Bem’s psychic plays the game all year round, never raises the stakes, and always quits at a profit of a million dollars, the expected return is $177,353,500. Clearly, Bem’s psychic could bankrupt all casinos on the planet before anybody realized what was going on. This analysis leaves us with two possibilities. The first possibility is that, for whatever reason, the psi effects are not operative in casinos, but they are operative in psychological experiments on erotic pictures. The second possibility is that the psi effects are either nonexistent, or else so small that they cannot overcome the house advantage. Note that in the latter case, all of Bem’s experiments overestimate the effect.


It did also cross my mind to ask if anyone has formulated a coherent model that would generate these kind of results as a statistical artifact without resorting to the psi hypothesis?

For example, a simple (and totally unsubstantiated) hypothetical alternative explanation. Suppose that on some level the negative stimulus in the Bem experiment (3 I think) where it is flashed up briefly after a response is regarded as a "wrong" answer by the participant. At some point, let's say half way through, the participant evaluates their performance so far - if they are doing "well" and frequently picking the image which isn't followed by negative imagery they continue to respond at the same speed. If they are doing "badly" and frequently picking the image which is followed by negative imagery they slow down their response times globally.

If this were the case (and I assume something like this could be tested for - measuring participants average response times as a function of how far through the test they had progressed), then it could alter the average response time for people who had done badly to be more weighted towards their responses in the second half of the test, where people who had done well would continue at the same speed and give equal weighting to the responses in both halves.

Of course that's a bit simplistic (and possibly horribly explained)... :shifty:

So, um any thoughts?
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Re: Daryl Bem's Presentiment Experiments

#62  Postby tnjrp » Apr 26, 2011 9:08 am

Wiseman's at it again:
http://www.badscience.net/2011/04/i-for ... s-problem/

The thick plottens... :think:
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Re: Daryl Bem's Presentiment Experiments

#63  Postby jerome » Apr 27, 2011 7:20 pm

tnjrp wrote:Wiseman's at it again:
http://www.badscience.net/2011/04/i-for ... s-problem/

The thick plottens... :think:



From my response to Ben's piece in the Guardian...

Ben makes some excellent points and also falls victim to a fallacy. He notes the failure of Wiseman, Richie, French to replicate Bem's results - as we might expect : but he fails to mention the successful replication by Batthany - (1) or the previous failed replication by Galak & Nelson (2).

But of course it gets worse - Ben seems to have accepted the media version of things by which Daryl Bem suddenly came up with the idea and found positive results around 2010 - but there is over a decades work on precognitive habituation, pioneered by Bem but taken up round the world.

Radin dedicates chapters to it, but offhand I can think of Savva Child & Smith 2005 (3) , a variant with spider pictures, then April 2009 saw "Moderating Factors in Precognitive Habituation: The Roles of Situational Vigilance, Emotional Reactivity and Affect Regulation" in the JSPR and back in 2007 we had Can a slide show presentiment effect be discovered in brain electrical activity?, Hinterberger et al (JSPR again I think.)

So Ben's science-lite comment ignores the fact parapsychologists have been pissing around for a decade with precog habituation, with varying degrees of success, and disagreement on whether the results actually show some precog effect or are just noise. As normal Dean Radin says they do, with massive statistical significance when meta-analysed - and others remain sceptical. But owing to the massive publication bias against replications that is the really important bit of Ben's comment, there is a tendency in academia and science to not repeat (replicate) but innovate, if only by changing a few variables here and there - and hence we still really have no idea.

We might expect this effect to be weak - Bem says it is; and we do not know what variables are involved. So what do we do? Replicate, keep a register, see what comes out. But Ben's article is damaging to the genuine scientific debate, and the worst type of media comment, because it implies strongly that Wiseman, Richie and French somehow ends it, that it means game over for Bem's claims; that now one failed replication has occurred all the papers should publish retractions - if so that would have happened with Galak's failure to replicate last November.

The truth is far more complex. There have also been successful replications, and this whole affair has been about spin on a set of experiments that have been after all messed around with for years, but were thrust t media attention when Bem published in a non-parapsi journal.

So as always the lesson here is don't trust opinions: check the sources. I don't know if precog habituation is real or not, though it could be (the actual effect claimed is hardly spectacular); it always makes me think of Benjamin Libet's famous experiments with the clock and response times, as if this would true it would alter their meaning somewhat. What I do know is that one failed replication d does not always tell us anything when the objects are humans, we don't know all the variables, and there have been successful replications. To juts push the most recent negative study as definitive is as much a fail as the press harping on about Bem's paper as "proof of psi" or whatever in the first case though.

(1) Batthyany, Alexander, (November 27, 2010) Retrocausal Habituation and Induction of Boredom: A Successful Replication of Bem Studies 5 and 7 http://papers.ssrn.com/sol3/papers.cfm? ... id=1715954

(2) Galak & Nelson (2010) http://papers.ssrn.com/sol3/papers.cfm? ... id=1699970
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Re: Daryl Bem's Presentiment Experiments

#64  Postby VK-machine » Apr 28, 2011 1:29 pm

Brilliantly misleading, as usual, Jerome... :roll:
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Re: Daryl Bem's Presentiment Experiments

#65  Postby jerome » Apr 28, 2011 4:32 pm

Go on then VK, correct me, you usually do :)

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Re: Daryl Bem's Presentiment Experiments

#66  Postby VK-machine » Apr 28, 2011 7:37 pm

jerome wrote:Go on then VK, correct me, you usually do :)

j x


Oh, Jerome, is that really necessary? Again?
I notice that the people at the Bad Science forum have already set you straight on your complete misunderstanding of Goldacre's piece.
Say, of how many replications are you aware?
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Re: Daryl Bem's Presentiment Experiments

#67  Postby Lazar » Apr 28, 2011 8:48 pm

jerome wrote:snip


My reading (or my biased reading at least) of Ben's point is a wider one than about psi. Indeed you seem to be reading from a subtext to his comments that I can't seem to see.

Largely I think he is lamenting two major problem with current social science and social science reporting:
1. Replication is not seen as serious scholarship.
2. The media tends to jump on the controversy but not how it plays out over multiple studies.
Both points are fair enough.

The larger problem however is that both you and Ben are talking about papers that have not been vetted by a peer review process which I think is rather pointless.
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Re: Daryl Bem's Presentiment Experiments

#68  Postby tnjrp » Apr 29, 2011 6:50 am

Lazar wrote:Largely I think he is lamenting two major problem with current social science and social science reporting:
1. Replication is not seen as serious scholarship.
2. The media tends to jump on the controversy but not how it plays out over multiple studies.
Both points are fair enough.
That looks mostly to be the point, yes. Especially since the readers of the article can't at least easily) even find the mentioned replication paper (the one that wasn't published)... :think:
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Re: Daryl Bem's Presentiment Experiments

#69  Postby jerome » Mar 14, 2012 11:26 pm

OK, a quick update on this --- as I keep saying not may area of interest, which is ghosts, but three failures to replicate reported here -- http://www.plosone.org/article/info%3Ad ... ne.0033423

Hope of interest!
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Re: Daryl Bem's Presentiment Experiments

#70  Postby jerome » Mar 15, 2012 6:12 pm

OK this has been all over the news and Twitter, so an informed perspective from, well me... http://jerome23.wordpress.com/2012/03/1 ... -by-media/
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Re: Daryl Bem's Presentiment Experiments

#71  Postby tnjrp » Mar 19, 2012 8:01 am

Again with added Wiseman!

Your piece was more interesting that the study, I'm afraid. But it is looking a bit like Daryl Bem didn't see the future either, doesn't it?
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Re: Daryl Bem's Presentiment Experiments

#72  Postby VK-machine » Mar 25, 2012 12:35 pm

This explains why the experiment doesn't replicate.
http://barenormality.wordpress.com/2012 ... replicate/
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Re: Daryl Bem's Presentiment Experiments

#73  Postby jerome » Apr 04, 2012 7:29 pm

Another critique from my blog, of Randi's giving Bem the Pigasus award this time -- http://jerome23.wordpress.com/2012/04/0 ... l-failure/ (Also include link to Bare Normality's post above, and the JREF thread. The mathematical analysis on the last page of that looks interesting and may interest VK too. )
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Re: Daryl Bem's Presentiment Experiments

#74  Postby jerome » Sep 05, 2012 8:55 pm

VK was right to point at Bem's scoring method on Experiment 8 on Bare Normality by the looks of things, though not had a chance to read this new paper properly yet, but have been through it once. Good stuff. It's on a failure to replicate Bem's Feeling the Future - Correcting the Past: Failures to Replicate Psi and you can download it an dread it at http://papers.ssrn.com/sol3/papers.cfm? ... id=2001721 and well worth reading. As I said before I'm still waiting with interest for the replication registry metaanalysis by Ritchie, French and Richard Wiseman. The emphasis on online experiments may be critical if the "relaxation phase" was missed -- but the paper dies discuss such variables. The meta-analysis has 12 studies, but there are others I believe, why Wiserman, Frenc & Ritchies replication registry so important.

However I won't blog on all this just yet -- because this Saturday at the SPR Conference there is CHRIS ROE, SARAH GRIERSON & AARON LOMAS: TWO INDEPENDENT REPLICATIONS OF DARYL BEM’S AUTOMATED PRECOGNITION EXPERIMENTS as well, and while I'll miss the presentation I hope to catch up with them on the Sunday. I'm still not convinced by Bem's effect, and even less so now, but after previous papers and discussion I'm staying cautious till I have seen more. Galak et al looks like a good and properly cautious paper though, unlike the reporting of it which will follow in next few days I expect :D

We will see!
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