Interactionist approach

Human behaviour is complex. Predicting human behaviour only on the base of one's genes is very difficult without knowing anything else about the person. We're dealing with over 20,000 genes and countless life experiences, so it would be wrong to assume life experiences do not affect behaviour, and that genes are solely responsible for behavioural traits.

The interactionist approach can be used to create complex models of behaviour by recognising that we need to look at factors beyond just one of the two extreme influences in the nature-nurture debate.

• First, we'll introduce the interactionist approach to psychology in the context of the nature-nurture debate.
• Next, we'll outline the interactionist approach definition.
• We'll follow by providing an interactionist approach example in psychological research.

• Then, we'll explore the interactionist approach in the psychology schizophrenia model.

• Finally, we'll dive into the interactionist approach psychology evaluation.

Fig. 1 - Predicting human behaviour based on one level of explanation (e.g. only based on one's biology) can be compared to predicting the area of a rectangle, knowing the length of only one of its sides.

Interactionist Approach Psychology: The Nature-Nurture Debate

The nature-nurture debate questions whether our traits are biologically determined (nature) or whether they are caused by environmental influences (nurture).

• The nature side of the debate argues that traits, behaviours, and disorders are caused by biological predispositions related to our genes, brain structure or physiology.

• While the nurture side highlights the role of the environment and upbringing in shaping the development of our psychological traits and behaviour.

The interactionist approach combines the arguments of nature and nurture to explain behaviours.

Interactionist Approach Definition

The interactionist approach explains the development of psychological traits, disorders, and behaviour as a product of both biological and environmental influences. It recognises that to explain and predict behaviour, we need to account for the interaction between both the influence of nature and nurture.

Phenylketonuria is a genetic disorder that affects how people process certain proteins. If left untreated, phenylketonuria leads to intellectual disability.

However, by diagnosing children early and putting them on an appropriate diet, the illness can be prevented. Despite the genetic vulnerability, an appropriate diet can prevent the expression of the genes that cause this illness.

Interactionist Approach Example In Psychology

The importance of the interactionist approach is highlighted by studies that show that these influences interact with each other. They show us that nature can influence our nurture and vice versa.

Nature can Affect Nurture

Scarr and McCartney (1983) identified 3 types of genome-environment interactions:

• Passive – we are provided the environment by our biological parents.
• Reactive – our temperament can influence how others react to us, which shapes our experiences.
• Active – our temperament and biological tendencies influence what kind of environments we seek out.

Nurture can Affect Nature

Nurture also mediates the relationship between genes and behaviour. This was demonstrated by the study of Turkheimer et al. (2003). The study investigated the heritability of IQ in a sample of twins and found that the heritability of intelligence depended on children's socioeconomic status.

• In children raised near or below poverty levels the heritability of IQ was close to zero (0.01), while in children raised in wealthy families the heritability of IQ was very high (0.72).

In summary, the heritability coefficients in Turkheimer et al. (2003) suggest that the relative contribution of genes to IQ depends on the socioeconomic status of the population.

Interactionist Approach In Psychology: Schizophrenia

The interactionist approach can also be used to understand the development of schizophrenia. In 1962, Paul Meehl proposed a model which explained schizophrenia as a result of having the schizophrenia gene (schizogene) and exposure to chronic stress in childhood (eg. being raised by a controlling and distant mother).

According to his model, stress in childhood only activates schizophrenia in individuals with a pre-existing genetic vulnerability. This model has later been developed, giving rise to the diathesis-stress model of schizophrenia.

The Diathesis-Stress Model argues that psychiatric disorders develop when biologically predisposed individuals are exposed to events that trigger the illness.

Most importantly, this model recognises the role of both the biological and environmental factors that lead to the development of a disorder. It can also explain why, when exposed to the same stressor, some people develop a psychological disorder while others don't.

The Role of Vulnerability in the Diathesis-stress Model

Family studies have demonstrated that genetic vulnerability is associated with a risk of developing schizophrenia.

Studies that investigated the genes linked to this disorder also indicated that schizophrenia is influenced by variations in multiple different genes.

How do the genes interact with stressors? The more genetic variations associated with the disorder a person has, the more vulnerable they are to the disease, meaning they need fewer environmental stressors for the disorder to develop.

Vulnerability can also be environmental, like growing up in a stressful environment.

Fig. 2 - Family dysfunction can increase individuals' vulnerability to developing schizophrenia.

The Role of Stressors in the Diathesis-stress Model

Stressors don't always refer to stressful events; a stressor is any event that is likely to trigger a psychotic episode. A common stressor for schizophrenia is drug use.

Wainberg et al. (2021) investigated the association between polygenic vulnerability for schizophrenia, cannabis use and experiences of psychosis in a large UK-based sample of 109,308 participants. Researchers found that participants with high polygenic vulnerability had a stronger association between cannabis use and psychosis.

• Highly vulnerable participants who used cannabis were 67% more likely to experience psychosis.
• Participants with low vulnerability participants that used cannabis were 7% more likely to experience psychosis.

These findings support the diathesis-stress model of schizophrenia.

Interactionist Approach Psychology Evaluation

One advantage of the interactionist approach is that it promotes holistic explanations of human behaviour and psychological outcomes. Models that follow the interactionist approach can account for different levels of explanation of a phenomenon. They consider biological influences like one's genetic vulnerability, social influences like one's socioeconomic status and the influence of nurture (e.g. upbringing and relationships with family members).

The interactionist approach has greater explanatory power than theories based only on nature or nurture influences. Combining various influences allows us to better predict individuals' traits.

This approach also has important implications for psychological treatments and interventions, for example, by identifying individuals at risk of schizophrenia we can inform them about potential triggers like cannabis use and minimise their future risk of developing the illness.

The interactionist approach also stresses the role of trauma and life events in the development of psychiatric disorders, and therefore the importance of addressing that during treatment through therapy in addition to medication.

Fig. 3 - The interactionist approach promotes holistic treatments to address mental health problems.