Core assumptions of the biological approach

The biological approach in psychology focuses on how physical and biological factors shape human behaviour. It provides a framework for understanding the link between the body and mind, emphasising the role of internal mechanisms over environmental influences.

Fundamental principles of the biological approach

• Biological underpinnings - Behaviour is largely influenced by biological factors such as hormones, genetics, evolutionary processes, and the nervous system.
• Potential for treatment - If behaviour is rooted in biology, undesirable or harmful behaviours, including those linked to mental illnesses, could potentially be altered or managed through biological interventions like medication.
• Animal research relevance - Studies on animals are valuable because humans share many biological similarities with other species, allowing insights into human behaviour and biological influences through experimental findings.

Basics of genetics and their influence on behaviour

Genetics plays a crucial role in shaping who we are, not just in terms of physical appearance but also in how we behave.

Key concepts in genetics

• Chromosomal structure - At conception, the fusion of egg and sperm results in 46 chromosomes, organised into pairs. Each chromosome consists of coiled deoxyribonucleic acid (DNA), which contains numerous genes.
• Role of genes - Genes carry the instructions that determine unique physical traits like hair or eye colour. Beyond appearance, they are vital in brain development, influencing behavioural tendencies.
• Genotype and phenotype - The genotype refers to the specific set of genes an individual possesses, while the phenotype describes the observable characteristics resulting from those genes, such as skin tone or height.
• Evolutionary perspective - Individuals with advantageous genes are more likely to survive and reproduce, passing on beneficial traits. Over generations, less advantageous genes are phased out. For example, behaviours like fear responses or aggression might have developed as survival mechanisms in early humans.

Genetic explanations for psychological traits

Genetics does not only influence physical attributes but also contributes to various psychological characteristics. Biological psychologists explore how inherited genes can affect mental and behavioural outcomes.

Psychological traits linked to genetics

• Behavioural differences - Traits such as gender-specific behaviours, intelligence, personality types, and sexual orientation are thought to have genetic components.
• Mental health risks - Certain genes are associated with an increased likelihood of developing mental health conditions or addictive behaviours.
• Inherited conditions - Faulty genes can lead to disorders with psychological impacts, such as Huntington's disease, which causes a decline in cognitive and emotional functioning.

Research methods for studying genetic influence

• Twin studies - These compare identical twins, who share 100% of their genes, with non-identical twins, who share 50%, to assess the genetic contribution to traits or disorders.
• Adoption studies - These examine individuals raised apart from their biological parents to distinguish between genetic and environmental influences on behaviour.

Research on the genetic basis of mental illnesses like schizophrenia

Schizophrenia, a severe mental disorder, has been extensively studied to uncover its genetic roots. Research using twin and adoption studies provides evidence for the hereditary nature of this condition.

Twin studies on schizophrenia

Twin studies investigate the likelihood of schizophrenia occurring in both twins, especially comparing identical and non-identical pairs to highlight genetic influences.

Gottesman (1991) meta-analysis of twin studies:

• Method - Analysed data from around 40 twin studies to evaluate the prevalence of schizophrenia across twin types.
• Results - Found a 48% chance of developing schizophrenia if an identical twin has the condition, compared to a 17% chance for non-identical twins.
• Conclusions - The higher concordance rate in identical twins strongly suggests a genetic component to schizophrenia.
• Evaluation:
  • The use of field studies enhances ecological validity, reflecting real-world scenarios.
  • However, since identical twins do not always both develop schizophrenia, other factors, such as environment, must play a role.
  • Additionally, identical twins are often treated more similarly than non-identical twins, which could influence outcomes beyond genetics.

Adoption studies on schizophrenia

Adoption studies help isolate genetic factors by studying individuals separated from their biological parents at a young age, focusing on inherited risks rather than shared environments.

Heston (1966) adoption study on schizophrenia:

• Method - Examined 47 adopted children whose biological mothers had schizophrenia, comparing them to a control group of 50 adopted children whose biological mothers had no such diagnosis. Participants were assessed as adults through interviews and tests for personality and intelligence.
• Results - In the experimental group, 5 out of 47 developed schizophrenia, and 4 others were rated as borderline schizophrenic. In contrast, none in the control group showed signs of schizophrenia.
• Conclusions - The higher incidence of schizophrenia in children of affected biological mothers supports a genetic basis for the disorder.
• Evaluation:
  • Interview data may be prone to bias, such as social desirability, affecting reliability.
  • However, the naturalistic approach of interviews provides rich, detailed insights.
  • There's also a possibility that control group participants could develop symptoms later in life, which cannot be entirely discounted.