Tag Archives: moon

Does the Moon Really Make You Crazy? Part 2


Sketch by Adan M. Garcia

This blog is a continuation of a topic discussed in Does the Moon Really Make You Crazy? Part 1. Make sure to pop on over to that blog first to set the scene and get some interesting statistics regarding the moon and crime rates.  If you don’t have time to read the whole thing, at least take a look at the last few paragraphs. Today’s blog is looking at a few other aspects of the lunar effect on behavior.


In my previous blog on this topic two studies showed a correlation between the frequency of certain types of crime and the phase of the moon. In this blog I will be looking at other ways the moon might influence behaviors like investment decisions and aggression. If market behavior is based more on emotion during the full moon, and aggressive impulses are also increased, it may be a sign that there is something to this moon theory.

The Moon and the Stock Market

“Moon Phase Effect on Investor Psychology and Stock Trading Performance” explores the connection between the full moon and investor performance. Basically the scientists were asking “Does a full moon mean less money and more aggressive behavior?” The short answer to that question in this study is yes. But before we take that data at face value, lets look a little bit at the methods. The study’s conclusion is based off of 202 Malyasian investors. This seems like a reasonable number to look at though, although it is important to note that some of the original subjects were dropped from the study for dissimilarities or failure to complete both periods of observation. This may create a bias towards responsible investors and ruin any randomization. This study was a prospective observational study that used surveys and investor data to observe any potential relationships. In order to assess chance, the scientists also did linear regression model simulations to look at trends there. The simulations, much like those done on the prayer problem in class, were used to see how many simulations resulted in similar results simply through chance.

The study found that there was a significant statiscal difference between the return made on investment during the regular moon phases and those made during the full moon phase. Behavior during the full moon tended to be more antagoinistic and less intellectual. In other words, smart financial men were ruled more by instinct during the full moon than otherwise. As always, this could be due to chance, a Type 1 error, or it could be correct. Confounding variables could also be involved here, but for the same reason we ruled out reverse causation in the previous blog, we must also do so here.

A Contrasting Study

“Does Full or New Moon Influence Stock Markets? : A Methodological Approach” looks at the same topic but finds a very different result. There are some benefits to this retrospective observational study, particularly its longevity. The study was conducted from 1962-1986. In my opinion, that makes the data a little stronger because it is supported over a long period rather than the two sessions examined in the previous study.  Over this length of time rises and falls of the stock market were compared to when they occurred in the lunar cycle. The researchers used multiple indices to compare and found that p>.05 and the correlations were not statistically significant. Of course since it is a study and not an experiment, the data may not indicate a correlation (or lack thereof). Reverse causation can be ruled out, but chance cannot, leaving the results susceptible to a Type 2 error.

Quite simply the decision I had to make here was personal. Which data holds more weight in my opinion based on the study methodology and results? Is there even a mechanism that could conceivably link the moon and strange behavior?

A Possible Mechanism

So we have evidence both from my first blog and this one that show a correlation between the moon and strange behavior (with the exception of the last study mentioned above). We also have years of anecdotal evidence that points to a possible relationship between the two. The word lunatic literally means “moon sick.” What mechanism could possibly create this body of evidence? Over several sources I have noticed a common theme between papers. Particularly this one. Scientists seem to think that the same gravitational pull the moon has on the ocean also pulls on the water in the human body. Since we are over 50% water, scientists hypothesize that the body has mini tidal waves that throw our systems out of whack. This could be the cause of behavioral changes.

What to Take Away

After looking at all the evidence in this blog series, I have come to the conclusion that there is some evidence that the moon affects behavior. There are studies out there, like the one above, that say the moon has no effect on certain things, but they are only a small proportion of all the studies looking for correlations. In my eyes that indicates that those are Type 2 errors, although we shouldn’t discount the idea that the file drawer problem may be affecting these results. The presence of multiple studies showing a correlation between the moon and strange behavior leads me to think that the idea has a solid base.  Although the mechanism is disputed, the section on tidal waves provides one possible explanation.

In conclusion:

The moon might very well alter your behavior, making you seem just a little crazy.

Let me know what you think of these findings. During the next full moon, pay attention to your

Vampire's Kiss (1989) Directed by Robert Bierman Shown: Nicolas Cage

Some people during the full moon.

behavior and those around you. Are they acting differently? Do you agree with my conclusions? Let me know in the comments below. If you haven’t already, check out and comment on my previous blog by clicking here.

That’s all for now.


Does the Moon Really Make You Crazy? Part 1

jw_full_moonAs I sat outside on Sunday, September 27th staring at the lunar eclipse, I began to wonder about that old ‘fact’ that says when there is a full moon you act differently. (Origin of the word lunacy anyone?) Could the movements of an object so far away from us influence our day-to-day activities?  We already know from Sir Isaac Newton that the moon can affect our tides, so is it possible it can affect our behavior as well?

What Constitutes Behavior?

Behavior, like many human attributes, can be difficult to measure. That being said, I had to narrow elements of behavior down into measurable variables. Even after doing that, there was simply too much information about different parts of behavior affected by the moon to process. I soon realized how impossible it would be to tackle more than one question about the lunar effect at a time. Because of this I have made the executive decision to divide this blog into two parts. The first part will look at the moon’s influence on criminal behavior.

The Moon and Crime

If human behavior is drastically influenced by the lunar cycle, it makes sense that there could be a notable increase or decrease in the amount of crime that occurs during a full moon. After some research it becomes clear that there are several studies examining this question.

Screenshot (18)

Image from study “Full Moons and Crime.” Graph belongs to C P Thakur and D Sharma.

“Full Moons and Crime” is an observational study exploring crime rates in relation with full moon days. As with any observational study, the data must be looked at through a skeptical lens because correlation need not equal causation. . The study did incorporate some elements of experiment by randomly selecting 3 towns to observe. Assuming the randomization was done properly, those three towns should give a fairly accurate depiction of the population as a whole. The study took place over 4 years, which contained 133 full moon days, which seems to be a good sample size. The null hypothesis in this case is that the moon has no effect on crime rate and the alternative is that it does. After careful analysis of all the crime records and what phase the moon was in when it happened, the researchers found a statistically significant difference in crime rates on nights when there was a full moon compared to nights in the rest of the lunar cycle. This evidence was strong enough that they rejected the null hypothesis in favor of a conclusion that the moon was influencing behavior.

What does all that data mean?
Basically, it means that there was significant statistical evidence that tied the full moon to increased crime rate. Unfortunately, this is an observational study that is extremely susceptible to confounding variables. For example, it may be easier to commit crimes when there is light provided by the full moon. In that case, the moon isn’t causing bad behavior, but is instead acting as a resource that inadvertently aids bad behavior. The good news is that reverse causation can be ruled out of this scenario due to nature’s laws. Regardless of what crimes humans do or don’t commit, the moon will still go through its natural phase shifts.

Now the really big issue. Can this data be generalized to more than just the population of these small towns? Since the study took place in India, are Indian and American people statiscally similar enough to generalize this information?

Why an Experiment Won’t Work

As we know from class, experiments are really the only way to prove that something causes something else. Unfortunately for us, there is no feasible way to perform an experiment on humans judging behavior when the full moon is out. Why? Because we can’t remove people from moon exposure to form a control group. It simply isn’t feasible to create an experiment without disrupting people’s lives completely. There are just too many variables that would require control. Because of this, we are stuck with looking only at observational studies.

If We Can’t Do an Experiment, Where Does That Leave Us?

Well we know that without an experiment, we can’t determine  a casual relationship, so what happens next? The answer is simple. Multiple observational studies can help to support a correlation by reducing the possibility of chance correlations. We still aren’t able to rule out third variables, but at least we would know that the statistics hold up in other parts of the world.

For example, in “Effects of the Full Moon on Human Behavior” (Click download PDF for the full text), researchers found that over a 1 year period of study in a large metropolitan area, 7 out of 8 types of crime, occurred at a statistically significant higher rate during full moon days than on a standard day. Homicide, the most serious crime included, was the only exception to this. Although this study doesn’t eliminate many of the problems discussed above, it does show that this phenomenon isn’t limited to just India. We still haven’t made in progress in determining if the relationship is casual because this study is also observational, but the evidence for some sort of relationship is piling up.

Why is Any of This Important?

So here’s the thing. Much like the depression and lights at night example talked about in class, it doesn’t matter why there is a correlation between the moon and increased crime rate, but rather that there is one. Even if the moon does not affect behavior, the truth is that two separate studies have shown increased crime rates during  full moon periods. In my opinion, it costs more to ignore the correlation than it does to acknowledge it. Regardless of the reason, crime is happening more frequently on nights with full moons. This information should be put to use as quickly as possible when discussing ways to reduce crime. If putting a few more police officers out on full moon nights can prevent increased crime, then what is the harm in doing it? The potential benefits outweigh the consequences.

What to Take Away

It looks like there is no conclusive proof that the moon makes you act differently, but the data in the two studies above are consistent with that hypothesis. In both studies, statistically significant differences, with p<.01, were found in crime rates on full moon nights compared with regular nights. This leads me to believe that regardless of whether the behavior is caused by the full moon, appropriate precautions should be taken by law enforcement on those nights. Does the moon alter your behavior? Possibly. Do we have irrefutable evidence? Not even close.


What do you think about the moon? Do you agree with my conclusion? Let me know in the comments below and keep an eye out for Part 2 of this blog series.

UPDATE: Part 2 is now posted. Click here to read about the moon and investing.

That’s all for now.