biological

• Charles Darwin proposed a theory called natural selection. The key point of this is that any genetically determined behaviour enhances the survival of the individual, and will continue into the generations allowing natural selection to occur. This can happen by certain traits having certain advantages compared to someone without them.
• Genotype is the genetic make-up and the phenotype is the way genes are expressed through physical, behaviour, psychological characteristics. Even if the twins genes are the same the phenotype is different.
•  limitation is that the biological approach is the biological determinism. This is because it sees human behaviour as internal, genetic causes which we have no control over. But we have already seen how the genotype is expressed, and how it is heavily influenced by the environment. Not even identical twins which share the same genes do not think the same. Also, a purely genetic argument is that it becomes problematic when it comes to crime. This suggests that the biological approach is simplistic and  ignores the mediation of the environment effects.
• Twin studies used to study certain psychological phenomena that have a genetic basis. This is achieved using concordance rates which is when the twins have the same characteristics. If they have all the same characteristics genetically it is monozygotic and if they only share half of the same genes genetically it is called dizygotic. For both of these cases the environment is determined to be constant.
• strength is that the biological approach is the scientific methods. This is because to investigate this they usually have to have highly precise and objective methods. These can be done by using advanced technology such as scans like fMRIs and EEGs. This can help improve the accuracy of the measure of physiological and neural proceeds which are not open to bias. This suggests that it's based on objective and reliable data.
• neurochemistry  refers to the actions of the chemicals in the brain. Most of human behaviour relies on chemical transmission within the brain, and this happens due to neurotransmitters. An imbalance in the neurochemicals can be a cause of a mental disorder.
• key assumptions of this approach is that everything is biological therefore to understand human behaviour they need to look at the biological structures. Also, thoughts, feelings and behaviour all have a physical basis.
• strength real world application. It has increased understanding of the neurochemical processes in the brain and these can be associated with the use of psychoactive drugs that treat mental disorders. Through this it has promoted the treatment of clinical and depression and antidepressant drugs, these can increase the levels of neurotransmitter serotonin at synapses in the brain. These drugs help reduce the symptoms of depression. This means that people with this condition may be able to manage it better and live their lives in the community rather than in hospital.