Full Moon Making You Act A Little Crazy? Think Again

Updated: Feb 13

Have you ever heard your teacher or parents say, “It must be a full moon,” as an explanation for your (or your classmates’ or siblings’) unusual behavior? For a long time, the full moon has been associated with unusual and bizarre human behavior. But the link between the moon and how people act has never been proven.

Photo via Shutterstock

Many studies have been done to try to prove that unusual human behavior is more common during a full moon, but so far the results have fallen short. In fact, when a group of researchers looked into more than 100 of these studies, they found none that could conclusively establish a connection between the full moon and human behavior.  


What they found was research that was conducted poorly or did not account for certain factors. For example, one study showed car accidents are more likely to occur during a full moon. But the data used for the study was collected on full moon nights that occurred on the weekend. It turns out accidents are more common on weekends no matter what the stage of the moon.


The theory behind the moon altering our behavior has to do with the gravitational force of the moon. The most well-known effect of this gravitational force is the oceans' tides. Because our bodies are about 80 percent water, the idea is that we may be susceptible to this gravitational force, just like the oceans. 


But science has shown that isn’t the case. Three key principles explain why the moon's gravity doesn't affect us like it does the oceans. First, the gravitational force of the moon is not powerful enough to effect human brain activity. Plus, the pull of the moon only creates tides in open bodies of water like oceans. Closed bodies of water, like the water in our bodies, are not affected by this gravitational force. And last, the gravitational pull of the moon is as strong during a new moon as it is during a full moon, and there are no theories or reports of unusual human behavior during the new moon. 


The myth of the full moon making people act abnormally has been around for centuries, even with no evidence to support it. One reason why is because the full moon theory is a popular storyline in movies and TV shows. 


A principle called the "illusory correlation" is also at play. The illusory correlation is the perception of a reality that does not exist. In this case, the perception is that the full moon affects how we act, although it has never been proven. Another example of the illusory correlation is people who experience joint pain saying it gets worse during wet, rainy weather. People often say this, but research shows it isn't true.


Illusory correlations exist because we usually remember things that did happen better than things that did not. If something unusual happens during a full moon, we often notice and even tell others about it. When nothing unusual happens during a full moon, there's nothing to remember or tell others about. 


It's also possible that many centuries ago the full moon did actually affect how we act. Some scientists believe the moon did lead to abnormal human behavior in the days before electricity allowed for indoor lighting and streetlights. In the days when many humans lived outdoors and slept under the light of the moon, a bright full moon could have made sleep more difficult, making people act different than normal.


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