The biological approach | AQA A-Level Psychology Revision
- Revision Notes
- Aug 3
- 16 min read
Updated: 7 days ago
For 7182 specification, first teach in September 2025
AQA A-Level Psychology | Free Revision Notes
Estimated study time: 55 minutes
These The biological approach A-Level Psychology revision notes explain how inherited genetic information, evolution, biological structures and neurochemistry may influence behaviour. You will learn to distinguish genotype from phenotype, examine how inherited characteristics may become more common over generations and consider how the brain, nervous system and chemical communication contribute to behaviour. The lesson follows the study of mental processing and prepares you to explore how biological and cognitive explanations can be combined in the study of brain-based cognition.
Learning Objectives 🎯
By the end of this revision page, you should be able to:
Define genotype and phenotype.
Explain the relationship between genotype, environment and phenotype.
Explain how inherited genetic information may influence behaviour.
Explain how evolution may contribute to behavioural characteristics.
Explain how biological structures influence behaviour.
Explain how neurochemistry influences communication within the nervous system and behaviour.
Revision Notes 📚
The biological approach A-Level Psychology revision overview
The biological approach explains behaviour by examining physical processes within the body.
Biological psychologists investigate influences including:
Inherited genetic information.
Genotype and phenotype.
Evolution.
The structure and functioning of the brain and nervous system.
Neurochemistry.
The approach assumes that thoughts, emotions and behaviour have a biological basis. This does not necessarily mean that the environment is irrelevant. Environmental experiences can interact with inherited characteristics and affect how a person’s phenotype develops.
The AQA specification requires students to understand the genetic basis of behaviour, genotype, phenotype, evolution and the influence of biological structures and neurochemistry.
What is a genotype?
A genotype is an individual’s genetic makeup.
It consists of the genetic information inherited from biological parents. This inherited information contributes to the individual’s potential characteristics.
A genotype is present from conception, although not every inherited characteristic is expressed in an identical way throughout life.
Genotype may influence:
Physical characteristics.
Biological functioning.
Behavioural tendencies.
Vulnerability to particular patterns of behaviour.
A genetic influence does not necessarily mean that a characteristic is unavoidable. Environmental conditions may affect whether and how an inherited tendency is expressed.
What is a phenotype?
A phenotype is an individual’s observable characteristics, produced through the interaction between genotype and the environment.
Observable characteristics can include:
Physical features.
Physiological characteristics.
Patterns of behaviour.
The relationship can be summarised as:
Genotype + environmental influence → phenotype
This does not represent a mathematical calculation. It shows that observable characteristics may reflect both inherited information and experience.
For example, two people may have different inherited potentials and experience different environments. These influences can contribute to differences in their observable characteristics.
Comparing genotype and phenotype
Genotype | Phenotype |
An individual’s inherited genetic makeup | The individual’s observable characteristics |
Present from conception | Develops through the expression of genetic information in an environment |
Refers to inherited information | Refers to what can be observed |
May create a potential or vulnerability | Shows how characteristics are expressed |
Does not change because of ordinary experience | May be influenced by environmental conditions |
A common examination task is to distinguish the two concepts.
A clear answer might state:
Genotype refers to the genetic information an individual inherits, whereas phenotype refers to the observable characteristics produced through the interaction of genotype and environmental influences.
How genotype and environment interact
The biological approach recognises the importance of inherited genetic information, but phenotype cannot always be understood from genotype alone.
Environmental influences may affect how a characteristic develops or is expressed.
These influences could include:
Learning experiences.
Social environments.
Physical environments.
Opportunities and experiences.
Exposure to stressors or support.
The same type of environmental experience may also affect people differently because their inherited characteristics differ.
This means that behaviour can result from an interaction between:
The individual’s genotype.
The environment in which development occurs.
The way inherited characteristics are expressed as a phenotype.
The wider question of whether heredity or experience is more important is developed through the interaction between heredity and environment.
Applying genotype and phenotype
Consider the following scenario:
Two siblings respond differently to a demanding situation. One remains calm, while the other becomes highly anxious.
A biological psychologist would not assume that the difference must have one simple cause.
The difference in phenotype could reflect:
Differences in the genetic information inherited by each sibling.
Differences in environmental experience.
An interaction between genetic and environmental influences.
A strong application answer should not simply state that the behaviour is “genetic”. It should explain how inherited characteristics could contribute to the observable response while recognising that phenotype develops within an environment.
The genetic basis of behaviour
The genetic basis of behaviour refers to the possibility that inherited genetic information contributes to behavioural characteristics.
Biological psychologists propose that genes can influence the biological systems involved in behaviour.
The sequence can be represented as:
Inherited genetic information → biological development and functioning → possible influence on behaviour
Genetic information does not usually operate separately from the rest of the body or the environment. It contributes to the development and functioning of biological systems that may affect how a person behaves.
For example, inherited information may influence:
The development of biological structures.
The functioning of the nervous system.
Neurochemical activity.
A person’s vulnerability to a particular behavioural pattern.
The behaviour itself is the phenotype. The inherited information contributing to it is part of the genotype.
Genetic influence is not genetic certainty
A genetic influence means that inherited information contributes to differences in behaviour. It does not automatically mean that an individual must display a particular behaviour.
It is therefore important to distinguish:
Genetic influence | Genetic certainty |
Inherited information contributes to the probability of a characteristic | An inherited factor guarantees a characteristic |
Environmental factors may also contribute | Environmental differences would make no difference |
Behaviour may result from interacting influences | Behaviour would have one unavoidable cause |
The biological approach identifies genetic contributions, but an observable behaviour may still be affected by experience and context.
⚠️ In an examination, avoid writing that a person behaves in a particular way “because they have the gene” unless the question provides evidence supporting that precise conclusion.
Investigating genetic influences
Psychologists investigating the genetic basis of behaviour compare patterns of behaviour and inherited similarity.
Their aim is to determine whether variation in genetic similarity is connected to variation in behaviour.
However, a relationship between genetic similarity and behavioural similarity does not automatically prove that genes caused the behaviour.
Researchers must also consider:
Shared environments.
Different experiences.
The way behaviour was measured.
Alternative biological or psychological explanations.
Whether the research design allows cause and effect to be established.
This illustrates an important distinction:
Evidence of a genetic contribution is not evidence that the environment has no influence.
What is evolution?
Evolution refers to changes in inherited characteristics across generations.
Some inherited characteristics may affect an organism’s ability to survive and reproduce. If a characteristic contributes to survival or reproduction, the inherited information connected with that characteristic may become more common in later generations.
The process can be summarised as:
Individuals vary in their inherited characteristics.
Some characteristics may provide an advantage in a particular environment.
Individuals with an advantageous characteristic may be more likely to survive and reproduce.
Relevant inherited information is passed to the next generation.
Across many generations, the characteristic may become more common.
Evolution occurs across generations. An individual does not evolve during their lifetime.
Evolution and behaviour
The biological approach proposes that behaviour, as well as physical characteristics, can be considered in evolutionary terms.
A behavioural tendency may have been favoured if it increased the likelihood that individuals would:
Respond effectively to their environment.
Survive long enough to reproduce.
Produce offspring.
Support the survival of inherited characteristics across generations.
From this perspective, some present-day behaviours may reflect tendencies that had survival or reproductive value in earlier environments.
An evolutionary explanation therefore asks:
How might this behavioural tendency have contributed to survival or reproduction?
The explanation must connect behaviour to inherited variation and changes across generations. It is not enough to say that a behaviour is useful.
Adaptive behaviour
An adaptive characteristic is one that helps an organism respond successfully to environmental demands.
A behavioural characteristic may be adaptive if it increases survival or reproductive success in a particular environment.
However, an evolutionary explanation must be used carefully.
A behaviour that appears useful today is not automatically evidence of evolution. Psychologists need evidence that:
Relevant inherited variation existed.
The characteristic affected survival or reproduction.
It was passed between generations.
The pattern became more common over time.
Evolutionary explanations concern why behavioural tendencies may have developed across generations, not simply why one individual acted in a particular way on one occasion.
Distinguishing genetic and evolutionary explanations
Genetic and evolutionary explanations are related, but they answer different questions.
Genetic explanation | Evolutionary explanation |
Examines how inherited information contributes to an individual’s behaviour | Examines why inherited behavioural characteristics may have become common across generations |
Focuses on differences or similarities between individuals | Focuses on selection across generations |
Connects genotype with phenotype | Connects inherited variation with survival and reproduction |
Asks how genes influence behaviour | Asks why a behavioural tendency may have been favoured |
A genetic explanation may describe the biological basis of a behavioural characteristic. An evolutionary explanation considers why inherited characteristics connected with that behaviour may have persisted.
Biological structures and behaviour
Biological structures are physical parts of the body involved in biological functioning.
Structures relevant to behaviour include:
The brain.
The spinal cord.
The peripheral nervous system.
Structures involved in communication within the nervous system.
Glands within the endocrine system.
Different biological structures perform different functions. Changes in the development, activity or functioning of these structures may therefore affect behaviour.
For example, the brain receives and processes information, while the nervous system carries signals between different parts of the body.
The organisation of these systems is studied in more detail through central and peripheral communication.
The brain and behaviour
The brain is a biological structure involved in processing information and coordinating behaviour.
Biological psychologists investigate relationships between:
Brain structures.
Patterns of brain activity.
Cognitive processes.
Emotional responses.
Observable behaviour.
If damage or altered activity in a biological structure is associated with a change in behaviour, psychologists may infer that the structure contributes to that behaviour.
However, association alone does not always prove that the structure caused the behaviour. Researchers must consider:
Whether the biological difference appeared before the behavioural difference.
Whether another variable affected both.
Whether several structures work together.
Whether environmental experience altered the biological system.
Specific brain functions and their locations are developed through the functions of different brain areas.
The nervous system and behaviour
The nervous system allows information to be transmitted throughout the body.
It enables an organism to:
Detect information.
Carry signals.
Process information.
Produce a response.
A person’s behaviour depends partly on effective communication between:
Sensory systems.
The brain and spinal cord.
Motor systems.
Different parts of the nervous system.
Changes in nervous-system functioning may therefore affect perception, thought, emotion and behaviour.
The different neuron types involved in this communication are examined in sensory, relay and motor communication.
What is neurochemistry?
Neurochemistry refers to the chemical processes involved in nervous-system functioning.
Neurons communicate using chemical messengers called neurotransmitters.
At a junction between neurons:
A signal reaches the end of a neuron.
A neurotransmitter is released.
The chemical crosses the gap between neurons.
It affects the activity of the next neuron.
Some neurotransmitter effects are excitatory, making the next neuron more likely to become active. Others are inhibitory, making it less likely to become active.
This communication process is explored fully in chemical communication between neurons.
Neurochemistry and behaviour
The biological approach proposes that behaviour may be influenced by the balance and activity of chemical messengers within the nervous system.
Neurochemical activity may affect:
Communication between neurons.
The activity of neural systems.
Information processing.
Emotional and behavioural responses.
A change in neurochemical activity could alter how signals are passed through the nervous system, which may then influence behaviour.
The explanatory sequence is:
Neurochemical activity → neural communication → functioning of biological systems → behaviour
A strong answer should make this connection clear. Simply stating that “chemicals affect behaviour” is too vague.
Excitation and inhibition
Neurotransmitters can influence whether another neuron becomes active.
Excitation | Inhibition |
Makes activity in the receiving neuron more likely | Makes activity in the receiving neuron less likely |
Supports the continuation of a signal | Reduces or prevents the continuation of a signal |
Contributes to neural activation | Contributes to the regulation of neural activation |
Behaviour depends on patterns of activity across biological systems rather than on every neuron becoming active at once.
The balance between excitation and inhibition helps regulate communication within the nervous system.
The endocrine system
The endocrine system is another biological communication system. It uses glands and hormones rather than communication between neurons.
Hormones travel through the bloodstream and can influence biological functioning and behaviour.
Nervous and endocrine communication differ in their methods, but both show how physical processes within the body may influence behaviour.
The role of glands and hormones is covered in hormonal communication in the body.
Connecting genes, structures and neurochemistry
The parts of the biological approach are connected.
Inherited genetic information may contribute to:
How biological structures develop.
How biological systems function.
Patterns of neurochemical activity.
These biological processes may then influence behaviour.
The relationship can be represented as:
Genotype → development and functioning of biological systems → phenotype
Environmental experiences may interact with the process at different stages. For example, experience may affect how a biological system develops or how a behavioural characteristic is expressed.
A biological explanation should therefore identify the level being discussed:
Genetic.
Evolutionary.
Structural.
Neurochemical.
Applying the biological approach
Consider the following scenario:
A psychologist finds that participants who show a particular pattern of activity in a brain structure also respond more quickly during a behavioural task.
A biological explanation could state that:
The brain structure may contribute to the processing required by the task.
Differences in its activity may be connected with differences in response speed.
The behavioural score is part of the observable phenotype.
However, the psychologist should not immediately conclude that the brain activity caused the behaviour. The evidence shows an association unless the study was designed to test cause and effect.
Applying genotype and phenotype to a scenario
Consider another example:
Maya and her sister grew up in the same household but respond differently to stressful situations.
A biological psychologist could explain that:
The sisters may not have identical genotypes.
Differences in inherited genetic information may contribute to differences in biological functioning.
Their experiences may also differ, even within the same household.
The different observable responses are aspects of their phenotypes.
Their phenotypes may result from interactions between genotype and environment.
This is more accurate than assuming that either genes or upbringing must provide the complete explanation.
Scientific strength: objective biological evidence
One strength of the biological approach is that biological variables can often be measured objectively.
Psychologists may collect evidence relating to:
Biological structures.
Nervous-system activity.
Neurochemical functioning.
Observable behaviour.
Objective measurements are less dependent on a researcher’s personal interpretation than vague descriptions of behaviour.
This can make biological explanations:
Testable.
Replicable.
Open to checking by other researchers.
Consistent with the empirical method.
However, an objective measurement is not automatically a valid explanation. Researchers must still show that the biological variable is meaningfully related to the behaviour being investigated.
Scientific strength: testable explanations
Biological explanations often produce predictions that can be investigated.
For example:
If a particular biological system contributes to a behaviour, variation in the system should be related to variation in the behaviour.
Researchers can then measure both variables and examine the predicted relationship.
Theories can be supported, refined or challenged according to the evidence. This is consistent with the scientific principles of hypothesis testing and falsifiability.
Limitation: biological determinism
Biological determinism is the view that behaviour is caused by biological factors such as genetic inheritance, biological structures or neurochemistry.
Deterministic explanations can be scientifically useful because they encourage psychologists to search for causes.
However, a strongly deterministic biological explanation may underestimate:
Conscious choice.
Learning.
Social influence.
Cultural context.
Differences in personal experience.
For example, identifying a genetic vulnerability does not mean that an individual is certain to display the associated phenotype.
The balance between biological causes and personal choice is examined through biological causes and human agency.
Limitation: biological reductionism
Biological reductionism explains complex behaviour at the level of genes, biological structures or chemical activity.
Reductionism can be useful because it breaks a difficult explanation into components that can be measured and tested.
However, reducing behaviour to one biological process may overlook:
Cognitive interpretation.
Emotional meaning.
Social relationships.
Environmental experience.
Cultural influences.
Interactions between different levels of explanation.
A neurochemical explanation may identify one part of the process without fully explaining why the behaviour occurs in a particular social context.
This issue is developed through different levels of psychological explanation.
Limitation: evidence may be correlational
Biological research may find a relationship between a biological variable and behaviour.
For example:
A pattern of biological activity occurs alongside a particular response.
People with similar biological characteristics show similar behaviour.
A biological difference is associated with a behavioural difference.
However, correlation does not establish cause and effect.
It may be unclear whether:
The biological factor influenced the behaviour.
The behaviour or experience influenced the biology.
Another variable influenced both.
A strong evaluation should therefore examine the research method rather than assuming that every biological association demonstrates causation.
Limitation: an incomplete explanation
Biological explanations can make an important contribution without providing the whole explanation.
A complete account of behaviour may need to consider several levels:
Level | Possible influence |
Genetic | Inherited information |
Biological | Structures and neurochemistry |
Cognitive | Mental processing and interpretation |
Learning | Conditioning and observation |
Social | Other people and social contexts |
Environmental | Experience and surroundings |
This suggests that the biological approach may be most useful when combined with other explanations rather than treated as the only possible account.
The similarities and differences between the main perspectives are considered in evaluating explanations across psychology.
The biological and cognitive approaches
The biological approach focuses on physical processes, while the cognitive approach focuses on internal mental processes.
Biological approach | Cognitive approach |
Examines genetic, structural and neurochemical influences | Examines information processing |
Investigates physical systems within the body | Investigates processes such as interpretation and memory |
May measure biological activity | Uses behaviour to make inferences about mental activity |
Explains behaviour at a biological level | Explains behaviour at a cognitive level |
The two approaches can be connected by investigating how biological activity relates to mental processing. This link is developed through brain activity and cognitive processing.
Overall explanation of the biological approach
The biological approach proposes that behaviour has a physical basis.
Its main assumptions are:
Genotype refers to inherited genetic makeup.
Phenotype refers to observable characteristics produced through genotype-environment interaction.
Genetic information may contribute to behavioural characteristics.
Evolution may explain why inherited behavioural tendencies became more common across generations.
Biological structures influence how information is received, processed and acted upon.
Neurochemistry affects communication within the nervous system.
Biological processes may interact with environmental experience.
The approach provides objective and testable explanations, but complex behaviour should not automatically be reduced to a single gene, structure or chemical process.
Key Words 🔑
Key word | Student-friendly definition | How it may be used in an exam |
Biological approach | An approach that explains behaviour through genetic, evolutionary, structural and neurochemical processes. | Outline the main assumptions of the approach. |
Genotype | An individual’s inherited genetic makeup. | Distinguish inherited information from observable characteristics. |
Phenotype | Observable characteristics produced through the interaction of genotype and environment. | Explain why people with genetic similarities may still differ. |
Genetic basis of behaviour | The contribution of inherited genetic information to behavioural characteristics. | Explain how inheritance may influence behaviour. |
Genetic influence | A contribution made by inherited information to the probability of a characteristic. | Avoid treating genetic explanations as absolute certainty. |
Evolution | Change in inherited characteristics across generations. | Explain why some inherited behavioural tendencies may have persisted. |
Adaptive characteristic | A characteristic that contributes to successful functioning, survival or reproduction in an environment. | Explain an evolutionary account of behaviour. |
Biological structure | A physical part of the body involved in biological functioning. | Explain how the brain or nervous system may influence behaviour. |
Nervous system | The communication system that detects information, processes signals and coordinates responses. | Link biological structures to behaviour. |
Neurochemistry | The chemical processes involved in nervous-system functioning. | Explain how chemical activity may influence behaviour. |
Neurotransmitter | A chemical messenger used in communication between neurons. | Explain how neural signals cross the gap between neurons. |
Excitation | A neurotransmitter effect that makes activity in the receiving neuron more likely. | Explain how chemical communication supports neural activity. |
Inhibition | A neurotransmitter effect that makes activity in the receiving neuron less likely. | Explain how neural activity is regulated. |
Biological determinism | The view that behaviour is caused by biological factors. | Evaluate the role given to choice and experience. |
Biological reductionism | Explaining complex behaviour at the level of biological components. | Evaluate whether the approach overlooks other influences. |
Interaction | The combined influence of two or more factors, such as genotype and environment. | Explain how phenotype develops. |
Common Mistakes ⚠️
Mistake: Using genotype and phenotype as though they mean the same thing.
Why this is incorrect:Genotype is inherited genetic makeup. Phenotype is the observable result of genetic and environmental influences.
How to improve:Use the distinction: genotype is inherited information, phenotype is expressed characteristics.
Mistake: Defining phenotype as appearance only.
Why this is incorrect:Phenotype includes observable characteristics, which may include patterns of behaviour as well as physical characteristics.
How to improve:Refer to observable physical, physiological or behavioural characteristics.
Mistake: Saying that the environment changes a person’s genotype.
Why this is incorrect:Ordinary environmental experience affects how inherited characteristics are expressed, not the inherited genotype itself.
How to improve:Explain that genotype interacts with the environment to contribute to phenotype.
Mistake: Assuming that a genetic influence guarantees a behaviour.
Why this is incorrect:Inherited information may create a tendency or vulnerability without making a behavioural outcome certain.
How to improve:Use terms such as “contributes to”, “influences” or “increases the likelihood” unless certainty is justified.
Mistake: Saying that an individual evolves during their lifetime.
Why this is incorrect:Evolution concerns changes in inherited characteristics across generations.
How to improve:Refer to selection and inheritance occurring over many generations.
Mistake: Explaining evolution by stating only that a behaviour is useful.
Why this is incorrect:Usefulness alone does not establish an evolutionary explanation.
How to improve:Connect inherited variation to survival or reproduction and transmission across generations.
Mistake: Saying that neurochemistry means thoughts are chemicals.
Why this is incorrect:Neurochemistry concerns chemical processes that affect communication and activity within the nervous system.
How to improve:Explain the chain from neurotransmitter activity to neural communication and then to behaviour.
Mistake: Naming a brain structure without explaining its relationship to behaviour.
Why this is incorrect:A label alone does not show how the biological structure contributes to the response.
How to improve:Explain the function of the structure and how differences in its functioning could influence behaviour.
Mistake: Assuming that an association between biology and behaviour proves causation.
Why this is incorrect:The behaviour may affect the biology, or another variable may influence both.
How to improve:Consider the design of the investigation before making a cause-and-effect conclusion.
Mistake: Describing the biological approach as entirely nature-based without recognising interaction.
Why this is incorrect:The approach emphasises biological influences, but phenotype may develop through interaction between genotype and environment.
How to improve:Distinguish a biological contribution from a complete biologically determined explanation.
Exam-Style Questions ✍️
Question 1
Which one of the following best describes phenotype?
A. Genetic information inherited at conception
B. Observable characteristics produced through genetic and environmental influences
C. Changes in inherited characteristics across generations
D. Chemical communication between neurons
[1 mark]
Question 2
Define genotype.
[2 marks]
Question 3
Distinguish between genotype and phenotype.
[4 marks]
Question 4
Explain how genotype and environmental experience may interact to influence phenotype.
[4 marks]
Question 5
Explain how evolution may account for a behavioural characteristic.
[4 marks]
Question 6
A psychologist finds that two people with similar inherited characteristics display different behavioural responses after growing up in different environments.
Using your knowledge of genotype and phenotype, explain this finding.
[4 marks]
Question 7
A researcher investigates a behavioural response in two groups of animals that differ genetically.
Group | Number displaying the behaviour | Total number in the group |
A | 18 | 24 |
B | 9 | 24 |
a) Calculate the percentage of animals in Group A that displayed the behaviour.
Use:
Percentage = number displaying the behaviour ÷ total number × 100
Show your working.
[2 marks]
b) Calculate the percentage of animals in Group B that displayed the behaviour.
Show your working.
[2 marks]
c) Explain why the results do not prove that genetic differences caused the behavioural difference.
[3 marks]
Question 8
Explain how biological structures and neurochemistry may influence behaviour.
[6 marks]
Question 9
Discuss the biological approach in psychology.
Refer to genotype, phenotype, evolution, biological structures and neurochemistry in your answer.
[16 marks]
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