Full Moon and Behavior
Date: January 2007
Why do people act crazy on a full moon?
They don't! Or not any more than usual. That is a legend or myth that has
persisted for a long time, but there is no evidence that it is true. A
scientist or any critical thinker will always look for supportable
before accepting any statement. Thanks for asking.
In this case, we need to begin by asking whether the phenomenon really
exists. What evidence do we have that people really do act crazy on a
full moon? Have we really measured the effect of a full moon on
people's behavior? If so, then we should also ask how reliable those
measurements are. This might sound like we're being overly skeptical
just for the sake of dismissing a neat mystery, but please understand
that this is how good scientists always work. We check and double-check
everything; it is called verifying our results. After all, it would be
wasteful to spend lots of time and energy working to explain something
that doesn't really happen.
So we always start by describing a phenomenon as carefully as we can.
We also should read about what other scientists have done to describe
the phenomenon. In the case of your question, several groups of
scientists have looked to see whether the full moon phenomenon really
happens, and to date, nobody has ever been able to demonstrate it
conclusively. A few studies have claimed to observe tiny increases in
rates of traffic accidents and small crimes during full moons. However,
most of those studies have subsequently been shown to be mistaken, for
various reasons. Because we don't have reliable evidence that the full
moon actually does influence human behavior, there is little reason for
us to spend time trying to come up with an explanation. Here is a very
good web site reviewing the full moon literature:
If you are interested in the full moon's influence on human behavior,
then I would encourage you to think about investigating the phenomenon.
Think about how you might measure "craziness" and how you could go about
making those measurements. Think about what kind of evidence would be
convincing to you and convincing to other people. Read the articles
referenced in the web site above and see what other scientists have
found. You can decide for yourself whether you agree with their
Please understand, skepticism does not mean that we should never take
mysteries seriously. There really are mysterious phenomena that are
easily observable and repeatable. For example, we find that objects
fall to the ground in a very reliable fashion and so that is a
phenomenon we would like to explain. We call that phenomenon gravity
and we have studied it and described it in great detail, but we can't
say that we really understand why it happens. Gravity is a natural
mystery that is well worth studying.
There is no scientifically studies that I am aware of that conclude that
people act crazier on full moon nights than at other times. It is a myth
that has been around for a long time, but I don't think it's true.
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Update: June 2012