The tradition and prospects of studying the mechanism of criminal behavior from the standpoint of modern biosocial interpretation of the phenomenology of human aggression

Bakharev Dmitry Vadimovich ORCID: 0000-0003-3922-3554 Doctor of Law Professor, Department of Public Law, Perm Institute of the Federal Penitentiary Service of Russia 614012, Russia, Perm Krai, Perm, ul. Karpinsky, 125 demetr79@mail.ru Other publications by this author

Aggression is one of the most complex forms of social behavior of animals in general, and humans in particular. A type of aggression is violence, including criminal. In general, the nature, forms of expression and intensity of an individual's aggressive behavior are an important characteristic of his personality. At the same time, if it is still established that aggression is based not only on contradictions arising during social interaction, but also endogenous (biological) factors, this will be able to correct the already established ideas about the personality of the criminal, existing not only in public opinion, but also among specialized specialists ^{[1, p. 59]}. 

Age correlates of aggressive behavior

So, what is known today about the age-related patterns of human aggression? Studies of its dynamics in the range from infancy to old age indicate that: a) people begin to show physical aggression before the end of the first year of life after birth, and b) the frequency of physical aggression peaks in the first 3-4 years after birth, and then decreases until old age ^{[2, p. 386-387]}. This is explained by the fact that "with age, children develop the ability to regulate these spontaneously occurring behavioral acts in accordance with the circumstances of the environment." Such regulation of behavior includes the development of the ability to control one's motivations and needs in accordance with the needs of other people and is "the main feature of socialization" ^{[3, pp. 673-674]}.

At the same time, the results of research in the field of behavioral sciences in the United States indicate that about 5% of boys consistently show signs of extreme antisocial behavior, and around this figure traditionally fluctuates both the proportion of men arrested by the police for the first time in adolescence, and the percentage of convicted adult young men for violent crimes, and the prevalence in the male population of persons with "antisocial personality disorder" (antisocial personality disorder). The presence of the syndrome of "persistent antisocial behavior" throughout life, American researcher Terry Moffitt fixes about 5-10% of all men; in her opinion, it has a biological basis in the form of dysfunctions of the nervous system. At the same time, its organic origin, she emphasizes, does not have exclusively biological determinism. Rather, individual differences in the state of the nervous system represent the source material for subsequent human interaction with the environment ^{[4, pp. 685-689]}.

Twin Studies

The level of heritability of aggression in twins in modern genetics is usually assessed as high ^{[5, p. 1142]}. In particular, the arguments in favor of moderate or high genetic influence (51-72%) on the likelihood of aggression in several thousand pairs of twins aged 3 to 10 years are presented by Dutch researchers, while boys have traditionally been assessed as more aggressive.

On the example of twins, attempts are also being made to identify neural correlates of aggressive behavior. In particular, a study using tensor morphometry and mapping the thickness of the cerebral cortex in 106 pairs of 14-year-old twin adolescents confirmed the involvement of the frontal-limbic-striated brain contour in the etiology of aggression in adolescence, and the anterior cingulate cortex and temporal regions were associated with aggression in adolescent twins ^{[6, pp. 230-240]}.

The neurobiological basis of aggressive behavior

Research in this field has now firmly established that emotions in the human brain are regulated by a hierarchically organized cortical-limbic chain consisting of the amygdala, prefrontal and anterior cingulate cortex, hippocampus, hypothalamus and a number of other interrelated areas ^{[7, p. 591]}. They are involved in the control of neural circuits that trigger defensive, aggressive or avoidant behavioral patterns. A special role belongs to the first three of them: excessive reactivity of the amygdala in combination with inadequate prefrontal regulation (due to changes in the anterior cingulate cortex) increases the likelihood of aggressive behavior ^{[8, pp. 260-261]}. This is evidenced by the results of research demonstrating a negative correlation between the activity of the orbitofrontal cortex and the amygdala in healthy people, and its absence in individuals with intermittent explosive disorder ^{[9, pp. 168-178]}.

 Neurochemical mechanism of aggression regulation

 The electrochemical impulse between nerve cells (neurons) is transmitted using neurotransmitters (neurotransmitters). One of them is serotonin, while its key role in controlling aggressive behavior is proven: it is serotonin that modulates activity in the prefrontal cortex (including the orbitofrontal cortex and the anterior cingulate gyrus), which are involved in the "descending" control of limbic response to stimuli ^{[10, pp. 557-558]}. In the development and regulation of aggressive behavior, the role of another neurotransmitter, dopamine, is also very significant today, although much less definite ^{[11, p. 77]}.

 The role and place of the endocrine system in the mechanism of aggression formation

The study of the neuroendocrine aggression circuit is mainly focused on assessing its effect on the formation of the hypothalamic-pituitary-gonadal and hypothalamic-pituitary-adrenal systems, in particular, hormones such as testosterone and cortisol. While studies of recent decades have been receiving more and more evidence in favor of the influence of testosterone and cortisol on aggression and related factors (for example, psychopathy), an unambiguous interpretation of this relationship is still quite difficult ^{[12, pp. 52-53]}. Apparently, it is influenced by factors such as age, gender and the degree of manifestation of signs of personal aggression and psychopathy. Cortisol and testosterone probably influence aggression and psychopathy by modulating the fear or threat circuit in the amygdala and prefrontal cortex ^{[13, pp. 270-271]}.

 The genetic foundation of aggression

 The active development of molecular genetics in recent decades has contributed to a surge of interest in the search for genes involved in aggressive behavior. There are two ways to solve this problem. The first of them is the study of candidate genes, the connection of which with a particular form of behavior is very likely. In relation to aggression, polymorphic variants of genes involved in the previously described mechanism of regulation of neurotrophy and functioning of neurotransmitter systems of the brain are naturally considered as such, and, first of all, involved in the metabolism of serotonin and dopamine (for example, monoamine oxidase A (MAOA), dopamine receptor 2 (DRD2), serotonin transporter (5-HTT or SLC6A4) and the dopamine enzyme catechol-O-methyltransferase (COMT). To date, many studies have been conducted, both confirming the association of polymorphism of these genes with various forms of aggressive behavior, and refuting this hypothesis ^{[2, p. 390; 8; 14]}. Such contradictory results are explained by the fact that the influence of individual genes on aggressive behavior is also mediated by the previous experience of their carriers, and especially by the conditions of early development and upbringing of such individuals ^{[3, p. 674]}. As noted by leading Russian experts in behavior genetics, "good parenting conditions, the presence of good parental care block the manifestation of aggressiveness genes, while poor conditions and lack of parental care contribute to the manifestations of aggressiveness. The same pattern was obtained in animal studies (rats, monkeys) and, apparently, is universal for animals" ^{[5, p. 1143]}.

Environmental (epigenetic) risk factors for the development of aggressive behavior

Epigenetics is the most actively developing field of genetic science in recent decades. It is based on the fact firmly established today that the activity of genes (expression), in addition to the actual genetic molecular factors, can be modified by other factors that do not affect the basic structure of DNA, i.e. epigenetic. As you know, each cell of the human body contains 46 chromosomes consisting of DNA and a protein base – nucleosomes. A network of nucleosomes packs chromosomes into a cell. So, thanks to the achievements of molecular genetics, it has been established that the protein base of the nucleosome can undergo chemical modifications (DNA methylation, histone acetylation, non-coding RNA, chromatin remodeling) that regulate gene activity. As a result, the same genetic "text" can be read differently in the cells of a multicellular organism, which makes them genetically identical, but structurally, compositionally and functionally heterogeneous due to differential gene expression. 

Such epigenetic changes largely depend on negative environmental influences, the implementation of which in early ontogenesis leads, among other things, to a change in the level of aggressiveness due to epigenetic modifications of gene functions. In particular, hypermethylation or increased acetylation of histones of a number of already mentioned genes involved in the regulation of neurotransmitter and hormonal systems (for example, the MAO-A gene), as a result of stress, unfavorable socio-economic conditions of early childhood, maternal smoking during fetal development and other negative effects during pre- and early postnatal development, it can destroy the conditions for the formation of a normal mechanism for suppressing aggressive behavior ^{[3, pp. 675-677]}.  

Thus, the socio-biological mechanism of aggressive human behavior is generally understandable. It involves the neurobiological, neurochemical and neuroendocrine systems of the body. The formation of their cells, as well as the cells of the whole organism, occurs on the basis of a given genetic program, but under the influence of epigenetic (environmental) influence, resulting in tissue-specific patterns of gene expression ^{[3, p. 676]}. Accordingly, environmental (social) factors can make a significant contribution to the process of ontogenesis.

Understanding the scheme and stages of aggression formation makes it possible to build algorithms for its personalized therapy, among which it is worth mentioning:

1) experiments on pharmacological correction of changes in epigenetic regulation of genes. In particular, one of the targets of pharmaceutical drugs is the genes of the immune system in order to regulate aggressive behavior by modulating serotonin metabolism ^{[15, p. 992]}.

2) improving the quality of nutrition. So, to date, most studies of the role of nutrition quality in the prevention of antisocial behavior are focused on assessing the role of omega-3 polyunsaturated fatty acids in this process. As is known, they are part of the cell membranes and blood vessels of the human body and are not synthesized in the right amount ^{[16; 17]}. Also, when investigating the role of poor-quality nutrition in the occurrence of behavioral problems in preschoolers, it was found that malnutrition or poor-quality nutrition (insufficient consumption of vegetables and fruits with, on the contrary, an excess of fast food, sweets and snacks) demonstrates a convincing relationship with a higher level of antisocial behavior even when leveling the role of heredity and the environment ^[18].

3) large-scale social programs in the field of crime prevention and deviance. The most famous of them is the non–governmental Program of interaction between nurses and families – Nurse-Family Partnership (NFP), implemented in the United States of America (see the official website – https://www.nursefamilypartnership.org /), aimed at improving the health and life of first-time mothers and their children suffering from socio-economic inequality and other risk factors. 

So, the above-described results of research on the biological side of human aggression quite convincingly suggest that its ignoring cannot be compensated by measures of socio-pedagogical impact of any scale, intensity and duration. Therefore, on the one hand, the formation of a full-fledged personality is impossible without taking into account its biopsychophysiological component, on the other hand, the biological side of the human nature of an adult individual is the result of the previous stages of his interaction with the outside world, as well as the peculiarities of such interaction of his parents, as well as several generations of their ancestors. Accordingly, it is very difficult with such an understanding of the mechanism of socialization to give a clear preference to its biological or social element. It follows from this that the synthetic, i.e. biosocial interpretation of the issues of phenomenology, genesis and public control over crime should become the fundamental basis for the formation of the vector of development of criminological science in the future.