A researcher investigates the genetic basis of a behavioral trait and finds a concordance rate of 68% for monozygotic (MZ) twins and 31% for dizygotic (DZ) twins.
According to the biological approach, which of the following is the most valid conclusion from this study?
The trait is entirely determined by genetic inheritance (genotype), because the MZ concordance rate is more than double the DZ concordance rate.
The trait has a genetic basis because the MZ rate is significantly higher than the DZ rate, but environmental factors also influence the phenotype because the MZ rate is less than 100%100\%100%.
The trait is entirely determined by environmental factors, because a concordance rate of 68%68\%68% in MZ twins shows that genetic factors are not sufficient to guarantee expression.
The genotype of MZ twins is modified by environmental influences over time, which explains why their concordance rate is below 100%100\%100%.
248 exam-style questions on AQA A Level Psychology Approaches in Psychology, covering Learning approaches, Cognitive approach, Biological approach, Psychodynamic approach (A-level only), Humanistic Psychology (A-level only), and Comparison of approaches (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.