One for the skeptics?

[mcromer]

The skeptics here mentioned a flaw with the presentiment studies. Basically, an expectation effect where the arousal continues to build before a negative stimulus, then is released.

I think they could be correct, this arousal building over time might well account for the presentiment effect. I would like to see a good explanation on why that cannot be the case from Bierman and/or Radin. That is why I do not have an article on presentiment on my AMNAP 2.0 blog. I have been thinking about this flaw and wanted to figure out which side is correct. I still don't know, but it seems at least plausible that the skeptical explanation can account for it. I'll be elaborating on this and posting it to my blog soon.

Good work, skeptics.

[jacob]

I wonder if Alex would be willing to ask Dr. Radin about this, now that they are acquainted.

But really, if I remember correctly, the presentiment study is the one which Alex found most interesting in Radin's work and which he often presents in the evidence debate, like in the latest podcast.

I've found it interesting as well, when reading Entangled Minds by Radin where he tells of the study as well.

[Topher Cooper]

About to leave on vacation so I can't check right now, but I pretty clearly remember a paper by Radin where he specifically analyzed this possibility -- it may have been part of his original presentiment presentation.

[jacob]

Following Topher's lead and googling for some info I've found the following article:
Conscious and non conscious emotional processes and the arrow of time
It looks like it's an original article by Radin and Bierman.

There I've found the following text:

Examining possible artifacts

Radin (1997) has adequately treated a number of potential normal explanations of the effect. The current replication, using completely different hardware and software, does strengthen the conclusion that the results are not due to technical artifacts.

The major (and maybe only) source of normal explanations remaining after Radin's original analyses is the hypothesis that subjects developed anticipatory strategies that resulted in different anticipatory physiology preceding calm or emotional pictures. At first glance this seems to be a real possibility. However, the current results do not support this idea because the presponse effect does not depend on the ratio between calm and emotional targets in any systematic way. We would expect some systematic relationship to exist if anticipation strategies were indeed based upon the Gambler's Fallacy.

There are three further arguments against an explanation in terms of normal anticipatory strategies. The first is that we find suggestive internal effects that can not easily be explained by this type of strategies. For example, the differences observed between erotic and violent emotional stimuli would require an anticipatory strategy (i.e., a probabilistic strategy) able to discriminate both between upcoming calm and emotional targets and between two types of emotional pictures. This seems most unlikely given that the subjects were blind both to the ratios between calm and emotional targets, and to the content of the emotional targets.

Secondly, sequential presentation histories starting with one emotional, followed by one, two or three calms always have a larger presponse before a final emotional in comparison with a final calm picture. Thus the effect is basically independent of presentation orders. Presentation orders starting with two or more consecutive emotional pictures and with larger lags are too infrequent to analyze.

The final argument is that computer simulations of anticipatory strategies, using the same emotional to calm target ratios and the same number of exposures used in the current studies, do not show the expected main calm vs. emotional effects. It does turn out that these simulations are sensitive for the type of randomization used. If we used a random selection with replacement of the targets, then the simulation effects were nil. However, if we used a random shuffling scheme without replacement then the effects ranged between 0% and 10%. This was a surprise because the reasoning as sketched in the introduction has such a direct appeal.

The following anticipatory strategies were tested:

a) Increase anticipation by 1 unit after each calm target, and reset anticipation to 1 after each emotional target.

b) Double the anticipation after each calm target (to a maximum of 500) and reset the anticipation after each emotional target to either half of the previous value, or 1.

The simulated effects in the open-deck situation were never larger than 2% while the observed experimental effects in Studies 1 and 2 were generally larger than 10%. However, these analyses are by no means exhaustive and there may be less plausible statistical anticipation models that may result in larger differences. The major point in favor of the psi hypothesis is that there are no indications in the real data that support any of these sequential strategy models.

[Rudism]

Here is the 2002 paper that I've seen which further explores different models of the expectancy effect (Bierman is listed as one of the authors). They reject Radin's initial dismissal of the effect, and show using computer simulations that under sufficiently short trial lengths, the expectancy effect can have a statistically significant effect on the results.

[mcromer]

Thanks Rudism.

That's a good paper to read and it corroborates the uneasiness I've always felt about the "presentiment" methodology. It always felt a bit too much like data artifacting to me.

That's not to say that it can't be real, but I'd like to see a strong case made that it cannot be an expectation effect. The way the original data analyses were conducted always smelled a little bit suspicious to me.

[David Bailey]

It seems to me that the key question is whether the presentiment effect varies with the length of the trial. That 2002 paper explains (very clearly) why the bias occurs, and it basically depends on the interaction between the arousal model and the sampling error (at least as I understand it). They have a graph showing how the bias tends to zero as the trial length increases.

Of course, this is made more complicated by the fact that subjects may get bored over longer trials!

Before everyone throws out presentiment as bunk, I think it is important to remember that strange timing effects to do with consciousness are nothing new (Libet). Some of the conventional explanations for that behaviour are pretty way out!

David

[alextsakiris]

Consider this (from a JREF blog post):

May and Spottiswoode. Experimental design addresses the expectation bias problems associated with previous designs
http://www.lfr.org/LFR/csl/library/SCpsr.pdf

http://www.lfr.org/LFR/csl/library/MPZjacm.pdf

(from: Pigasus Awards & Sheldrake - Page 4 - JREF Forum)

You might also post to Entangled Minds.
He's pretty good about responding.

I want to do a series of shows on these experiments. It gets more and more interesting the further you dig.

[mcromer]

Thanks Alex. That first paper pretty much blows the expectation effect out of the water, since they test for it specifically and it isn't present. I'll have to do more reading later.

[Rudism]

Originally Posted by mcromer

Thanks Alex. That first paper pretty much blows the expectation effect out of the water, since they test for it specifically and it isn't present. I'll have to do more reading later.

What I got from that paper is that it was (or could be) present, but they did a bunch of statistical analyses on the data in an attempt to show that it couldn't actually account for the results they obtained.

A better approach, in my opinion, would be to come up with an experiment that rules out expectancy effect by design. While possibly more difficult to do, this would be much more compelling than trying to rule it out by doing a bunch of fancy number shuffling around some assumptions about how it may or may not affect the data.