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1.4.5. Genetic factors

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For a long time, the influence of parents was conceived as a cause and the adaptation of their children as an effect. The two main theoretical schools, behaviorism and psychoanalysis, although so traditionally opposed, come together to conclude that the way parents educate the child, and what parents do to the child, is extremely important. The spectacular improvements brought about by adoption, or the effects of educational intervention, have shown the crucial effect of the family environment.

At the end of the 1960s, a complementary hypothesis was put forward: children are not only receptors, but they also influence the behavior of their parents. A child’s behavior is partly influenced by genetic factors; it is therefore possible to maintain the idea that the parents’ behaviors play a crucial role in the adaptation of their children, but with the addition that these behaviors are caused by characteristics of the child under genetic influence.

Behavioral genetics has had a profound influence on how developmental psychologists view how family influences affect children in different ways.

Today, the influence of the family environment on the child can be defined by three main components:

 – the influences of genetic factors: genes that parents pass on to each child;

 – shared environmental influences: a family environmental characteristic is so massive that it has effects on all children in the family, for example, abject poverty, religious orientation or strong conflict between parents;

 – the influences of the non-shared environment: each child is not subject to the same effects due to various causes. For example, girls are not raised in the same way as boys (even today), the mother has a stronger attachment to a particular child, the socioeconomic situation of the family has changed or a particular characteristic of the child under genetic influence causes different reactions in the parents.

Over the past 20 years, research has highlighted the importance of the non-shared environment. Parents are always surprised by this phenomenon: “how and why are my two children so different when they have had the same education?” Well, no! Also, there are two types of effects of the non-shared environment: “differential positivity” (one child receives significantly more of something than the others) and “differential negativity” (one child receives significantly less of something than the others).

Shared and non-shared environments are also related. For example, a common characteristic of the family context (stress, marital discord, lack of money, too many siblings, composition of the siblings) will exacerbate the difference in treatment between children. This is because parents will have limited resources to devote to each child. When stress occurs, it will diminish the resources available and they will be forced to concentrate them on one child.

We can thus be led to the paradox that differences in the way parents treat each child are attributable to aspects of family life that are shared by all children. Finally, differential parental treatment is not necessarily pathogenic: it all depends on whether it is experienced by the child as fair or unfair. For example, the child accepts it when the differential treatment depends on the age or special needs of his or her siblings.

From this framework, two types of work can be conducted. On the one hand, “child-based” studies: the child’s genes are the unit of measure and do not directly influence the way the parents treat them, but indirectly, through the parents’ reaction to the child’s characteristics; for example, siblings are compared with each other. On the other hand, the rarer “adult-based” work: the parent’s genes are the unit of measure and we study the role played by genetic proximity on parental behavior, for example, the behavior of mothers who are twins.

We will therefore define:

 – genotype/environment interaction: genetic factors influence sensitivity to an environment. For example, divorce has more negative effects on children with a genetic vulnerability to depression; negative life events are a non-shared environmental factor that explains the differences between monozygotic twins in the occurrence of depression. Overly coercive family discipline is a risk factor for adolescent depression, but only in certain social settings;

 – genotype/environment correlation: genetic factors select or cause exposure to different environments. For example, a child’s physical attractiveness causes positive reactions in parents, educators or peers.

Three types of correlations between genotype and environment are therefore distinguished. These types correspond to three mechanisms by which the genetically influenced characteristics of an individual affect his or her experiences:

 – passive correlation: parents and children share the same genotype and the same environment. For example, parents pass on genes related to a difficult trait and express this difficult trait through irritable and negative parenting behavior, which in turn is related to the child’s difficult trait. In a child-based construct, this correlation would be categorized as “shared environment influence”, whereas in a parent-based construct, it would be categorized as “genetic factor influence”;

 – evocative or reactive correlation: this results from a reaction of the environment to a characteristic of the child under the influence of genetic factors. Parents react to the child’s difficult character with harsh and negative parenting, a “coercion cycle”; a happy child provokes different reactions from a gloomy child, for example. There is a growing acceptance of the idea that children influence how they are treated by others, including their parents, and that parents react differently depending on the child. Adoption studies are the most relevant in highlighting evocative correlations, as they provide information about the biological parents. For example, if we know the psychopathology or addiction of the biological parents, then we can see how it increases the risk of such problems in the adopted child, problems that will in turn influence the parenting behavior of the adoptive parents;

 – active correlation: the child actively selects environments that are correlated with his or her genetic characteristics (this is more often true for peers than for parents) or that his or her perceptions of events are genetically influenced (a suspicious child will generally perceive his or her parents’ behavior more negatively than a confident child and will act accordingly; a depressed adolescent will isolate himself or herself and inhibit influences from his or her parents).

We must understand all these processes that build parental behavior and its adaptation to the child if we want to be able to improve dysfunctions and their consequences.

Child Psychology

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