What Is Stochastic Variation In Psychology? Neither Genes Nor Environment

Part of our way of being is not given by genes or by specific events that we live.

What is Stochastic Variation in Psychology

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

With the passage of 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 it is not really like that? 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 describing the idea of ​​noise in more depth, giving various examples and relating it to personality traits.

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 determinism, that is, each one was born with their genes that configured how they were going to be, without any modification during their life.

Others, on the other hand, 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 environment (“nurture”) intensified throughout the last century, but by the end of the same the influence of these was agreed, in a Solomonic way. two aspects: “fifty-fifty”. Genes and environment were equally influential, perhaps one more in some ways and the other in others.

Much of the research has focused on finding out how the environment influences genetics, under the belief that if all influences are known, it is possible to predict aspects such as diseases and mental disorders, in addition to the development in personality, physical and mental. This certainly makes a lot of sense, but the problem is that the research showed that genes and environment did not explain 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, it will be because they were raised separately, to having lived in different environments.

The problem is that 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 do you explain all this? This question has an answer, which is not that it is very elegant but it seems to apply to 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 manifest 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 right and left sides 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 a behavior, let’s call it capricious, of the cells that make it up, rather than genetics or environment.

The name of noise is not accidental. Scientists have called this variable noise because, like sound noise, it is unpredictable, not systematic. Trying to isolate the noise and measure it is something that could be called at least paradoxical. 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 stimuli, but you cannot control or change the variation, it is there.

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

One of the laws of nature is that organisms that reproduce asexually are genetically very homogeneous. This has a pros and a cons. The pro is that the passing of genes to the next generation is guaranteed, since there are hundreds of replicas of the same genome, but there comes the con, and that is that since they are all the same, if your genome is not adaptive, it will hardly be to survive one before an unfavorable environment. But this was not the case with the little crabs.

Despite their genetic uniformity, marmorkrebs show differences 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 equal, environmental influences should not be ruled out. Marmorkrebs raised in a temperate climate may have adapted to fit it, while others have adapted to cold climates. Nature has put the situation on them and they have known how to adapt to it. But there are too many differences in the same population for this to be the case.

This is a clear example of how genetics and the environment do not have control of absolutely everything in the development of an individual. If so, it would be expected that all individuals of marmorkrebs would be the same in a given region, but this is not the case. Even those who live in the same river, with the same environmental factors and the same genetics, show differences. Something in their cells has whimsically been activated to make them different.

Stochastic Variation in Psychology

Stochastic variation seems to play a very important role in terms of personality traits. Returning to the aforementioned of the twins, who does not know identical twins raised in the same house that are like night and day? There are not a few pairs of monozygotic twins who, despite having the same genome and (almost) the same environment, behave very differently, even showing very notable differences such as tastes, school performance, sexuality or political ideology.

Apparently, during development, brains are organs in which there is more stochastic variation, 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 big unexpected changes in the behavior and personality of the individual once they have matured.

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

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

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

Bibliographic references:

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

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