What is stochastic variation in psychology? Neither genes nor environment

Part of our way of being is given neither by genes nor by concrete events that we experience.

Genetics and environment have aroused a great and long debate during the history of psychology. During the last century there were many who defended the position of genetic determinism, while others claimed that, if environmental influences were controlled, any posture in an individual could be strengthened.

With the passage of time, the scientific community settled the dispute by agreeing that these two aspects were equally influential, half one and half the other, but what if this is not really the case? What if 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 attributable neither to genes nor to environment.This is an idea that we are going to explain by describing the idea of noise in more depth, giving several 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 proponents of genetic determinismthat is, each person was born with his or her genes that shaped how he or she was going to be, without any modification during his or her life.

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

Debates about which was more important, genetics ("nature") or environment ("nurture") intensified throughout the last century, but by the end of the century the influence of these two aspects was agreed upon in a Solomonic way: "fifty-fifty". Genes and environment were equally influential, perhaps one more in some aspects and the other in others.

Much of the research has focused on finding out how the environment influences over and above genetics, under the belief that if the environment has a greater influence than the genetics, then the genetics will have a greater influence than the environment.The belief has been that if all the influences are known, it is possible to predict such things as disease and mental disorders, as well as personality, physical and mental development. This certainly makes a lot of sense, but the problem is that research has shown that genes and environment do 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 performed with identical twins separated at birth. To the extent that they differ, it is because they were reared separately, because they were will be because they were raised separately, because they 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 the same class, being dressed in the same way and so on, they have some differences. Sometimes these differences are very noticeable, such as political preference, tastes or sexual orientation, how to explain all this? This question has an answer, which is not a very elegant one, but it seems to be valid for the scientific community: it is because of noise.

Even within 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 side of the face, the body and the brain, and genetics does 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 to genetics or environment.

The name noise 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 you cannot predict? 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 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 species of small lobster that inhabited waters of all kinds: the marmorkrebs..

These small crustaceans suddenly appeared, being classified as a new species. Apparently, probably during 1995, some individual domestic crab underwent a mutation that allowed it to reproduce asexually, causing all its offspring to constitute a new species, all of them females capable of reproducing from unfertilized eggs. One of the mutants escaped and reproduced rapidly, threatening ecosystems.

One of the laws of nature is that organisms that reproduce asexually are very homogeneous genetically. This has a pro and a con. The pro is that the genes are guaranteed to be passed on to the next generation, since there are hundreds of replicas of the same genome. since they are all the same, if their genome is not adaptive, it will be 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, the 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 the same, environmental influences should not be ruled out. Marmorkrebs bred in a temperate climate may have adapted to adapt to it, while others have adapted to cold climates. Nature has put them in the situation and they have been able to adapt to it. But there are too many differences in the same population for that to be the case.

This is a clear example of how genetics and environment do not control absolutely everything in the development of an individual. If they did, one would expect that all marmorkrebs individuals would be the same in a given region, but this is not the case.but this is not the case. Even those living in the same river, with the same environmental factors and the same genetics, show differences. Something in their cells has been activated in a capricious way to make them different.

Stochastic variation in psychology

Stochastic variation seems to play a very important role in personality traits. Going back to the twins mentioned above, who does not know identical twins raised in the same house who are like night and day? There are many pairs of monozygotic twins who, despite having the same genome and (almost) the same environment, behave very differently, and even have very notable differences in taste, school performance, sexuality or political ideology.

Apparently, during development, brains are the organs in which most stochastic variation occurs, i.e., random variation.. Some neurons connect, others lose connections, synapses here and synapses there. It looks like chaos, a situation that, apparently, is what can make big unexpected changes in the behavior and personality of the individual once he or she has matured.

Many genes 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, one could perhaps measure the importance and capacity of such unpredictable noise.

This This was observed in the experimental setting, but with flies.. A 2013 investigation 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 showed intraindividual differences, with asymmetries between the left and right hemispheres. It was these asymmetries, which seemingly came 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 looking at their behavior, the scientists attributed between 35% and 40% of the flies' behavior as a result of chance, i.e. noise. The scientists themselves went so far as to claim that, depending on the character, noise would be responsible for 50% of the variability of personality and behavioral traits..

Bibliographical references:

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