Saturday, 11 April 2015

You Can't Blame Loonies on The Full Moon

OMG! The Lamb of God has appeared on the end of the Isle of Wight!
This must be a sign!
Stop blaming the moon: Intelligent people can develop strong entirely incorrect beliefs -- ScienceDaily

An article published a few days ago in Nursing Research shows how easy it is for people to misinterpret data to see a pattern where there is none. Professor Jean-Luc Margot took the data used in a 2004 paper which purported to show a correlation between the number of people admitted to an emergency department suffering from gastro-intestinal bleeding and the incidence of full moons.

The errors came from imprecision with the method used to calculate the 'full moon days'. Most people assume the lunar cycle is a 28-day cycle whereas it's actually a 29.5 day cycle. This means that in some lunar cycles, in some places, the day on which the moon was 'full' was actually day 30 of the cycle, not day 29 as the authors of the 2004 paper had seemed to assume.

The other difficulty is in estimating exactly when a 'full' moon occurs. Technically, a moon is only ever fully illuminated over the whole of the Earth-facing disk when seen from Earth is when the sun, Earth and moon are perfectly aligned, yet when that happens, the moon is eclipsed by Earth, and in any case, would only be full when seen from within the narrow track of the eclipse. Even if we ignore that we need to decide exactly when the moon became full in relation to midnight - and why use midnight as the demarcation?

So, even if we get the 'full moon' day right, we need to consider how full it is at the location under consideration. If we back off from this strict definition of fullness, what degree of incomplete fullness is accepted as full? 90%, 99%, 99.9%? Obviously we can't chose a definition which isn't achieved in some locations in some cycles but if we set the bar too low, we might have more than one day of fullness in a cycle.

When these corrections were applied to the 2004 paper, any apparent increase in admissions were removed and there was no statistically significant differences in the 'full moon' days and the non full moon days.

Incidentally, it's worth downloading the full article from the PDF link on the above site because it contains both the response of the authors of the 2004 paper and Margot's reply, and to read the discussion section in which Margot lists some of the causes of cognitive bias:

For me the real significance of this paper is the reference to the role of 'cognitive bias' in misinterpretation of data:

Gilovich (1993) provided a lucid and compelling explanation of several cognitive biases that affect the emergence of questionable beliefs. First, we are not very good at recognizing random data and tend to see patterns, clusters, and order even where these don’t exist. Second, we are prone to ignore data that contradict our beliefs and to give undue weight to confirmatory information (i.e., data that support preestablished beliefs). Third, we tend to overestimate the fraction of people who share our beliefs, which reinforces preexisting beliefs. Gilovich (1993) emphasized that many of our questionable beliefs have purely cognitive origins and derive primarily from the "misapplication or overutilization of generally valid and effective strategies for knowing." Questionable beliefs, he stated, are not the products of irrationality, but rather of flawed rationality.

Kelly et al. (1996) classified some of the cognitive biases under three categories:selective perception (we are more likely to notice events that support our beliefs than those that do not), selective recall (we are more likely to recall positive instances and forget negative ones), and selective exposure (we are more likely to associate with people or news sources that promote our beliefs). All of these effects are much more complex and interesting than the gravitational force exerted by an ordinary natural satellite. Research efforts devoted to understanding these cognitive biases are far more likely to yield productive results than another study of the imagined influence of the Moon on human affairs.


If even people who try to be scientific in their methods can fall victim to it, how much easier must it be for people who not only aren't scientific in their approach but consciously disavow the scientific method?

It's not too hard to extend this into other areas of belief even where those holding them are convinced there is evidence to support them. We see it every day where theists of all flavours and creeds are convinced the 'evidence' supports theirs and theirs alone while dismissing everyone elses claims as flawed or mistaken, or even falsified, misrepresented or just plain stupid - too silly to be taken seriously. Yet to an objective outsider such as an Atheist, they all appear equally implausible and lacking in credibility because they can all easily be explained as perfectly natural, or dismissed as non-existent because the 'evidence' can never be produced and has never been validated.

  • Selective perception: that sunset, birdsong, butterfly, lottery win, surviving an earthquake, even the birth of a baby, will be ascribed as the work of a god - Jesus, Allah, Ganesh, Vishnu, etc.
  • Selective recall: remembering when something went right but not when it went wrong - the prayer was answered (hundreds weren't) - God is great! God answers prayers.
  • Selective exposure: all my friends believe in god (I don't like Atheists/people who believe in other gods) and there is lots of stuff supporting me in the news (I don't listen to stuff about all those wrong religions).

See that picture of the sheep on the Isle of Wight? Who would think that was a sheep who had never heard of sheep? Why not a white bull, or a fat corgi? Who would think it was the 'Lamb of God' who wasn't a Christian? And who would see it as a sign from a god who didn't believe gods send signs? It is, of course, a chalk cliff, eroded by wind, rain, frost and wave action. And yet people build little shrines where a dropped icecream looks a bit like a woman in a wimple, 'just like the Virgin Mary wore', treat vague face-like shapes in toast as signs and even take pictures of clouds that look vaguely like the Arabic for Allah and claim them as proof of Islam.

To the cognitively biased, the fact that NOT being scientific gives the required answer whereas science tends to counter it, is merely confirmation that science doesn't work. Cognitive bias rules!

So, we should be careful not to ascribe idiotic religious superstitions to something like the Moon. Religious fundamentalists might be loonies but that doesn't mean they can blame the Moon.

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1 comment :

  1. The full moon thing is really convincing to a lot of people who otherwise aren't really superstitutious.

    I've tried explaining to them that it doesn't make much sense, even when they babble about gravity and the oceans, because the whole moon is there every night, whether or not it's lit.

    But Alan Watts once said that "The world is nothing but a Rorschach ink blot," and every day, that seems more and more true.

    Of course, maybe I'm just looking for a Rorschach ink blot!

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