Sunday, 21 June 2009

Talking of mass hallucinations

Some people think that events such as Miracle of the Sun at Fatima are miracles. Others, working on good Humean principles say that such an event can't be a miracle, since if the sun really danced in the sky, it would have been noticed elsewhere, and that it must have been something more to a mass hallucination. Richard Dawkins takes this line in The God Delusion when he says "after all, Portugal isn't that isolated".

But this leaves us still with the need to explain what really was going on. Just saying it was a "mass hallucination" doesn't really do the matter justice. Calling it that is explaining-away, not explaining, unless you can offer an idea as to why mass hallucinations take place, and whether events at Fatima could reasonably be regarded as a characteristic example.

Some of the possible elements are already well-described - possible freak meteorological conditions, the fact that people had been encouraged to stare at the sun, the fact that most witnesses were devout Christians and already inclined to believe in miracles. But how is it that so many concluded that this particular event was a miracle?

One interesting clue comes from an entirely unrelated book. I've been having tremendous fun reading "Bad Science" by Ben Goldacre. Those of you you have read my Guardian articles will know that I'm something of a fan of Goldacre, and have cited his article on homeopathy more than once as an outstanding example of how to rationally approach a problem where clear thinking is needed to identify what the evidence is actually showing.

The most outstanding chapter in his book is entitled "Why Clever People believe Stupid Things". It is only 14 pages long, but the book is worth its price just for those 14 pages. In it, Goldacre describes the ways in which we commonly fool ourselves because human cognition is not well-adapted to dealing with certain situations. He talks of cognitive illusions and compares them with optical illusions. The cognitive illusions he describes are as follows
  1. We see patterns when there is only random noise.
  2. We see causal relationships whre there are none.
  3. We overvalue confirmatiory information for any given hypothesis.
  4. We seek out confirmatory information for any given hypothesis.
  5. Our assessment of the quality of new evidence is biased by our previous beliefs.
  6. Our assessment of the quality of new evidence is biased the prominence with which it is brought to our attention.
  7. Our beliefs are strongly affected by social pressures to conform.
I strongly recommend you buy this book, if only for his explanation of these points. The rest is highly entertaining and informative as well.

This last item is particularly relevant to cases of apparent mass hallucination. Goldacre describes Asch's experiments into social conformity.
The subjects were placed near one end of a line of actors who presented themselves as fellow experimental subjects, but were actually in cahoots with the experimenters. Cards were held up with one line marked on them, and another was held up with three lines of different lengths - six inches, eight inches, ten inches.

Everyone called out in turn which line on the second card was the same length as the first. for six of the eighteen pairs of cards, the accomplices gace the correct answer; but for the other twelve, they called out the wrong answer. In all but a quarter of cases, the experimental subjects went along with the incorrect answer, defying the clear evidence of their own senses.
Given this, it is now easy to see how such a mass hallucination might come about. The subjects were phsyically and mentally weakened by events, already inclined to believe in miracles, so once word spread that a miracle had occurred, many people would (without any intent to deceive) interpret their understanding of events in order to conform. Of such things are miracle stories born.

The next chapter in Bad Science is "Bad Stats", in which he describes how journalists habitually misunderstand statistics and present them in misleading ways. Hmmm.

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