Happy Birthday, Harold Davenport!

The great Cantabrigian Harold Davenport is believed to have been the first to calculate the surprising statistic that only 23 people need be gathered together for there to be a 50% probability that two have them will have the same birthday. This work has however been somewhat undermined by rolling lockdowns, which make such a gathering seem unimaginable for the foreseeable future.

It has been suggested that many of our false beliefs are the result of the apparent inability, demonstrated by the birthday problem, most of us have in predicting such probabilities. And that many so-called anomalistic experiences can be explained away by the high probability of such so-called coincidences occurring when the Law of Large Numbers, as opposed to the rule of six, is in force.


Telephone telepathy, where you think about someone you haven’t heard from for a while shortly before they call you, and precognitive dreams, where you dream about something just before it happens in reality, are phenomena that yield easily to this law of large numbers: with some 7.8 billion people on the planet, how unlikely is it for someone somewhere to have such experiences?


There are, for example, over 21 million people on the planet today who share a birthday with Harold Davenport, and while it would seem to me to be something of a curious coincidence if I were one of them, this is only because of an egocentrism which leads me to falsely believe that my experience is not equivalent to that of any of those other 21 million.


Whether or not a poor grasp of probability really does contribute to false beliefs in psychic powers and if it does how big a factor it is, is unclear from the current research. One thing that is clear however is that, while I do not share a birthday with Harold Davenport, the fact that I am, as I have just noticed, writing this on that very day is a curious coincidence of absolutely no significance.

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