What is stochastic variation in Psychology? Neither genes nor environment

Genetics and environment have aroused a great and long debate during the history of psychology. During the last century there were not few who defended the position of genetic determinism, while others They claimed that if environmental influences were controlled, any position could be strengthened in a individual.

Over time, the scientific community settled the dispute by agreeing that these two aspects had an equal influence, half one half the other, but what if this is not really the case? What if the behavior is also due to random, unpredictable factors? This is where the idea of ​​noise comes in.

Stochastic variation in Psychology is understood as the variation in personality and behavior that is not attributable to genes or the environment., an idea that we are going to explain by further describing the idea of ​​noise, giving various examples and relating it to personality traits.

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Genes, environment and noise? stochastic variation

It is practically a mantra that various aspects of each one, that is, their individual differences, are a mixture of two factors: genetics and environment.

Some were supporters of genetic determinismThat is to say, each one was born with his genes that configured how he was going to be, without any modification during his life.

Others, instead, relied on the environment, combined with environmental and social influences., to change aspects such as the personality and intelligence of the individual.

Debates about what was more important, whether genetics (“nature”) or the environment (“nurture”) intensified throughout the last century, but by the end of it the influence of these two aspects was agreed upon, in a Solomonic way: “fifty-fifty”. The genes and the environment influenced equally, perhaps one more in some aspects and the other in others.

Much of the research has focused on figuring out how the environment plays a role over and above genetics., under the belief that if all the influences are known, it is possible to predict aspects such as mental illnesses and disorders, as well as personality, physical and mental development. This certainly makes a lot of sense, but the problem is that with the research it was seen that genes and environment do not it explained all the variability, especially in cases of genetically identical individuals with the same environment.

Everything that is not attributed to genetics is attributed to the environment. This is how it is usually concluded in many experiments carried out with identical twins separated at birth. To the extent that they differ, that It will be because they were raised separately, having lived in different environments.

The problem is that in identical twins raised in the same environment, raised in the same home, going to the same school, even to the same class, being dressed in the same way and a long etcetera, present some differences. Sometimes these differences are very noticeable, such as political preference, tastes or sexual orientation, how can all this be explained? This question has an answer, which is not very elegant, but it seems to be valid for the scientific community: it is because of the noise.

Even in the same individual there are differences between cell and cell with the same function. Thus, it has been seen in cells that some show an erratic behavior, typical of a tumor cell, while others of the same type do not. Going to larger structures, we have differences between the left and right side of the face, the body and the brain, and genetics do not explain this factor. That the face is not exactly symmetrical could be due to behavior, let's call it capricious, of the cells that make it up, rather than genetics or the environment.

The noise name is not accidental. Scientists have called this variable noise because, like sound noise, it is unpredictable, not systematic. Trying to isolate noise and measure it is something that could be called paradoxical to say the least. How do you measure what cannot be predicted? You can play with the genome, you can play with the environment, you can play with physiology, activating certain cells, controlling the stimuli, but you can't control or change the variation, is there.

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The curious case of the marmorkrebs

In the 1990s a new species appeared in parts of Europe, Japan, and Madagascar. A kind of small lobster that lived in waters of all kinds: the marmorkrebs.

These small crustaceans appeared suddenly, being classified as a new species. Apparently, surely during 1995, some individual domestic crab suffered a mutation that allowed it to reproduce asexually, causing all their offspring to constitute a new species, all of them females capable of reproducing from unfertilized eggs. Someone escaped one of the mutants, which reproduced rapidly and threatened ecosystems.

One of the laws of nature is that organisms that reproduce asexually are genetically very homogeneous. This has a pro and a con. The pro is that the passing of the genes to the next generation is guaranteed, since there are hundreds of replicas of the same genome, but here comes the con, and that is Since they are all the same, if their genome is not adaptive, it is difficult for any of them to survive in an unfavorable environment. But this was not the case with the small crabs.

Despite their genetic uniformity, marmorkrebs differ in color, size, behavior, and even longevity. Despite being clones, they are different, they have diversity. Common sense would tell us that, well, despite being genetically the same, environmental influences should not be ruled out. Marmorkrebs bred in a temperate climate may have adapted to suit it, while others have adapted to cold climates. Nature has given them the situation and they have known how to adapt to it. But it is that there are too many differences in the same population for it to be so.

This is a clear example of how genetics and the environment do not control absolutely everything in the development of an individual. If it were so, one would expect that all individuals of marmorkrebs would be the same in a given region, But is not the case. Even those who live in the same river, with the same environmental factors and the same genetics, present differences. Something in their cells has been activated in a capricious way so that they are different.

Stochastic Variation in Psychology

Stochastic variation seems to play a very important role as far as personality traits are concerned. Going back to the aforementioned about twins, who doesn't know identical twins raised in the same house who are like night and day? There are not a few pairs of monozygotic twins that, despite having the same genome and (almost) the same environment, behave differently. very differently, they even present very notable differences such as tastes, school performance, sexuality or ideology policy.

Apparently, during development, the brains are organs in which more stochastic variation occurs, that is, random variation. Some neurons connect, others lose connections, synapses here and synapses there. It seems like chaos, a situation that, apparently, is what can make great unexpected changes in the behavior and personality of the individual once they have matured.

There are many genes that have been found that allow us to understand both the anatomical and behavioral variation of people, which would be behind their individual differences. By altering these genes, perhaps the importance and capacity of such unpredictable noise could be measured.

This was observed in the experimental setting, but with flies. A 2013 investigation carried out by Hassan's group found this random connection and disconnection of neurons in the brains of these insects that were genetically the same. The neural connections of these flies varied from individual to individual, despite all having the same genome and rearing in the same way. They even presented intra-individual differences, with asymmetries between the left and right hemispheres. It was these asymmetries, apparently appearing out of nowhere, that would explain the differences in their behavior.

In fact, based on their experiments, modifying both the genome of the flies and seeing their behavior, the Scientists attributed between 35% and 40% of the behavior of flies as a result of chance, this is the noise. The scientists themselves came to affirm that, depending on the character, noise would be responsible for 50% of the variability of personality and behavioral traits.

Bibliographic references:

• Masotti, A. L. (2000). Genetic, epigenetic, and behavioral stochastic variability and the individuation process. Imago schedule 45.
• Linneweber, G. A., Andriatsilavo, M., Bias-Dutta, S., Bengochea, M., Hellbruegge, L., Liu, G. … Hassan, B. TO. (2013). A neurodevelopmental origin of behavioral individuality in the Drosophila visual system. Science, 367(6482), 1112-1119.