Serial killing follows predictable pattern based on brain activity

Jan 18, 2012 by Lisa Zyga report
A graph of the cumulative number of murders committed by Andrei Chikatilo over 12 years. The irregular plot is a “Devil’s staircase.” Image credit: Simkin and Roychowdhury

(PhysOrg.com) -- Over a period of 12 years, Andrei Chikatilo murdered at least 53 people before being arrested in Rostov, Russia, in 1990. While Chikatilo’s killings, mainly of women and children, may have been senseless, a new study has found some sense in the distribution of intervals between the murders, which closely follows a power law. The researchers propose that the murder activity can be explained by a model describing neuronal firing in the brain, very similar to the model that describes the distribution of intervals between epileptic seizures.

The researchers, Mikhail Simkin and Vwani Roychowdhury, both electrical engineers from the University of California, Los Angeles, began their analysis by making a graph showing Chikatilo’s cumulative number of murders over the 12-year period. The graph is highly irregular, with long time periods with no murders interrupted by short time periods with many murders. The shortest interval between murders was three days, while the longest was more than two years. Due to this irregularity, and the step-like appearance of the plot, mathematicians call this distribution a “Devil’s staircase.”

Next, the researchers graphed the distribution of intervals between murders, clearly showing that short intervals are more common than long intervals. Somewhat surprisingly, this distribution of intervals between murders is very similar to the distribution of intervals between , with both following a similar power law. Simkin and Roychowdhury note that previous research has suggested a link between epilepsy and criminality (and psychosis), so the possibility that similar processes in the brain may lead to both epileptic seizures and serial murders is not unreasonable.

The researchers previously proposed a based on the brain’s neuron firing to explain the distribution of intervals between epileptic seizures, and here they’ve applied the same model to explain the distribution of intervals between murders. They hypothesize that the simultaneous firing of a large number of neurons in the brain induces psychotic effects that cause a serial killer to commit murder, similar to the effects that induce epileptic seizures.

Distributions of intervals in the Devil’s staircase plot closely obey a power law simulation. Short intervals between murders occur much more often than longer intervals. Image credit: Simkin and Roychowdhury

The researchers explain that the probability of any neuron firing randomly is small. But since the axon of one neuron can connect to the synapses of thousands of other neurons, if that neuron fires then its impulse could cause others to fire if they’re close to the firing threshold. The model predicts that the killer commits murder when the total number of firing neurons reaches a certain threshold - or “murder zone” - for a certain period of time. During this time of abundant neuron firing, the killer plans, prepares, and carries out the crime.

The model assumes that committing a murder has a sedative effect on the killer, causing neural excitation to fall below the threshold. (Otherwise, the neural excitation would be in the murder zone for half the total time.) But neuron firing must still be close to the threshold, since the probability of a new murder is significantly higher in the days after a murder compared to the average murder rate.

Although the model closely approximates Chikatilo’s behavior, the researchers note that it’s not exact. The biggest disagreement is that the model predicts several one-day intervals between murders, while Chikatilo’s shortest interval was three days. The researchers think that accounting for successful and unsuccessful murder attempts could improve the agreement between the model and data.

Although it’s difficult to tell if understanding the patterns of a serial killer will help prevent murders, the fact that any kind of rational explanation may exist for seemingly irrational behavior is both uncomfortable and revealing.

Explore further: New 'Surveyman' software promises to revolutionize survey design and accuracy

More information: M.V. Simkin and V.P. Roychowdhury. “Stochastic modeling of a serial killer.” arXiv:1201.2458v1 [physics.soc-ph]

via: Physics arXiv Blog

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User comments : 12

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deerkaa
not rated yet Jan 18, 2012
Yay!
Argiod
1.4 / 5 (10) Jan 18, 2012
Great! Now we can stop calling serial killers 'murderers', and send them to a psychiatrist instead... and pay even more tax payers dollars to support these worthless animals; instead of taking them directly out of the human gene pool.
bredmond
5 / 5 (8) Jan 19, 2012
Great! Now we can stop calling serial killers 'murderers', and send them to a psychiatrist instead... and pay even more tax payers dollars to support these worthless animals; instead of taking them directly out of the human gene pool.


but if we can find out the mechanism for it, maybe we can treat it or prevent it, and then we don't have to spend as much tax payers money in trying them in court, housing them or executing them depending on the law. Or moreover, the victims and their families wont have to suffer because they wont be getting murdered to begin with.
Deathclock
2.6 / 5 (5) Jan 19, 2012
Great! Now we can stop calling serial killers 'murderers', and send them to a psychiatrist instead... and pay even more tax payers dollars to support these worthless animals; instead of taking them directly out of the human gene pool.


It's probably the case that free will is an illusion and who you turn out to be is entirely dependent on circumstances beyond your control, beginning with the circumstances you are born into, which you clearly have no control over.
jsdarkdestruction
5 / 5 (1) Jan 19, 2012
how do they know exactly how many people he killed? I've read alot on his case and they say AT LEAST 53 for a good reason as far as i know. he himself didnt even know he'd lost count with how many he'd killed.
n0ns3ns0r
5 / 5 (2) Jan 19, 2012
Great! Now we can stop calling serial killers 'murderers', and send them to a psychiatrist instead... and pay even more tax payers dollars to support these worthless animals; instead of taking them directly out of the human gene pool.

rawr rawr rawr outrage
Don't worry. Science will never take away your freedom to outrage.
bredmond
not rated yet Jan 19, 2012
i wonder if addiction follows similar patterns, or other crimes like petty theft. i read somewhere that a lot of people steal just for the fun of it, not because of any financial need. and addictions like gambling, smoking, drinking, sex, etc. and also eating. i wonder if we factor in eating habits (i.e. frequency of meals, volume of meals, content of meals), how will that correlate with the data.
pres68y
2.3 / 5 (3) Jan 19, 2012
Seems like Andrei is just what the military is looking for!
Killers without a conscience are their ideal soldiers.
Oops, I forgot they are called "freedom fighters"... ha-ha
that_guy
1 / 5 (1) Jan 19, 2012
They'll just implant a chip in your head, and as soon as it detects that you've reached the murder threshold, you'll be arrested for premeditated murder without regard to the fact that your murder threshold only applies to murdering three quarts of ice cream.

j/k. Have fun with the conspiracy theorists :)
julianpenrod
1 / 5 (5) Jan 21, 2012
This "study" is a fraud. Anyone who wants to grab some quick, dishonest fame or grant money, ytou declare some hot topic to "follow a power law". It's been done for tornadoes, earthquakes, "terrorism". But it's all a trick, "Proving" a "power law" involves taking the logarithms of data and showing they form a straigh line graph. But logs "squash" data immensely, so even weird collections of data can look like a straight line! Incidentally, even random data form a straight line, or slope 0. Neutrons, shoes, clouds, snowflakes, battleships, A5 stars "wear out" by different processes, but graphing the logs of ther time to wearing t\out to their mass would produce a straight line, which could be used to say they "follow a power law".
cerium
5 / 5 (1) Jan 23, 2012
What bugs me most about this kind of unconfirmed theories is the conclusions that are quickly drawn from them by the so called popular scientists. Come on! Did you really think that serial killing has no rational explanation?! Is there any thing in the world of science that may have no rational explanation?! And what does having a rational explanation have to do with the absence of free will?! It only shows that committing a murder may have a sedative effect on the killer, as other actions may have a similar effect too.
Deathclock
1.3 / 5 (3) Jan 24, 2012
And what does having a rational explanation have to do with the absence of free will?!


I never said it did, I was making a separate point. It's easy to get mad at people and want to punish them, it's harder to ask whether or not they actually had any control over their outcome in life. They certainly had no control over the circumstances they were born into, and that certainly has a significant impact on where you end up in life. Perhaps we should do away with the archaic notion of punishment and instead focus on prevention. Of course I am still in favor of removing people from society who cannot function according to the rules of that society, but mostly because I don't think we have the capability to successfully change these people through rehabilitation. Maybe some day...