Neurotransmitters, chemical signals produced by a nerve cell and released to the target cell. Revision Notes

Neurotransmitters are chemical substances produced by nerve cells, also known as neurons. Their primary function is to carry messages from one neuron to another or from neurons to other types of cells, such as muscle or gland cells. This chemical communication is essential for the nervous system to coordinate bodily functions and responses to the environment.

Unlike electrical signals that travel within a neuron, neurotransmitters enable communication between cells by crossing the synaptic gap, a tiny space separating neurons or between neurons and their target cells.

• Neurotransmitters are chemicals that transmit signals between cells.
• They are produced inside neurons.
• They enable communication across the synapse.

Neurotransmitters are synthesized within the neuron, often in the cell body or axon terminals. Once produced, they are stored in small sacs called synaptic vesicles located at the end of the neuron’s axon.

For example, the neurotransmitter dopamine is produced from the amino acid tyrosine inside neurons and stored until needed. This storage allows the neuron to release neurotransmitters quickly in response to an electrical signal.

• Synthesized inside neurons from precursor molecules.
• Stored in synaptic vesicles at axon terminals.
• Ready for rapid release upon stimulation.

When an electrical impulse, called an action potential, reaches the end of a neuron, it triggers the synaptic vesicles to fuse with the neuron's membrane, releasing neurotransmitters into the synaptic cleft (the gap between neurons).

These neurotransmitters then diffuse across the synaptic cleft and bind to specific receptors on the membrane of the target cell. This binding causes changes in the target cell, such as initiating another electrical signal in a neuron or causing a muscle to contract.

For example, acetylcholine released at neuromuscular junctions binds to receptors on muscle cells, causing muscle contraction.

• Action potential triggers neurotransmitter release.
• Neurotransmitters cross synaptic cleft.
• Bind to receptors on target cells.
• Trigger responses in target cells (e.g., neuron firing, muscle contraction).

Neurotransmitters can affect various types of target cells:

Other neurons: influencing whether they fire their own action potentials.

Muscle cells: causing contraction or relaxation depending on the neurotransmitter and receptor type involved. For example, acetylcholine causes skeletal muscles to contract but can cause smooth muscle relaxation in other contexts depending on receptor type. Gland cells: stimulating or inhibiting secretion of hormones or other substances.

• Target cells include neurons, muscle cells, and gland cells.
• Effect depends on receptor type and neurotransmitter.
• Can excite or inhibit target cell activity.

Neurotransmitters are essential for rapid and precise communication within the nervous system. Without them, neurons could not influence other cells to coordinate complex behaviours, reflexes, or physiological processes.

For example, the neurotransmitter serotonin influences mood and social behaviour, while dopamine is involved in reward and movement control. This chemical signalling underpins everything from muscle movement to emotional responses.

• Enable communication between neurons and other cells.
• Allow complex coordination of body functions.
• Different neurotransmitters have specialised roles.

Serotonin is a chemical messenger, or neurotransmitter, produced by nerve cells in the brain and other parts of the body. It transmits signals between neurons by crossing synapses, the gaps between nerve cells. Serotonin is involved in regulating many functions including mood, appetite, sleep, and social behaviour.

Unlike hormones that travel through the bloodstream, neurotransmitters like serotonin act locally and rapidly to influence target cells. Serotonin’s effects depend on the brain regions and receptor types it activates.

• Serotonin is a neurotransmitter involved in brain communication.
• It regulates mood, emotions, and social behaviour.
• It acts quickly and locally between nerve cells.

Serotonin helps regulate mood and emotional states. Higher serotonin activity is generally linked to feelings of well-being and calmness, while low serotonin levels are associated with mood disorders such as depression and anxiety.

Mood influences how people interact socially. When serotonin levels are balanced, individuals tend to be more emotionally stable and better able to engage positively with others. This creates a foundation for prosocial behaviours, which are actions intended to benefit others.

For example, a person with healthy serotonin function may feel more empathy and patience, making them more likely to help a stranger in need.

• Serotonin regulates mood and emotional stability.
• Balanced serotonin supports positive social interactions.
• Mood affects willingness to engage in prosocial acts.

Prosocial behaviour includes helping, sharing, cooperating, and showing empathy. Research indicates that serotonin plays a key role in promoting these behaviours.

Experimental studies have manipulated serotonin levels using drugs or dietary changes and observed effects on social behaviour. For instance, increasing serotonin can enhance cooperation in economic games where participants decide whether to share resources.

One explanation is that serotonin reduces impulsive or aggressive responses, allowing more thoughtful and socially beneficial decisions. It also enhances sensitivity to social cues, improving understanding of others’ feelings and needs.

• Prosocial behaviour involves actions benefiting others.
• Higher serotonin levels promote cooperation and empathy.
• Serotonin reduces impulsivity and improves social sensitivity.

Consider a workplace scenario where a team member with balanced serotonin levels is more likely to offer help to colleagues and resolve conflicts calmly. This behaviour supports group success and harmony.

In contrast, low serotonin may lead to irritability or withdrawal, reducing prosocial actions and harming social bonds.

Another example is in charitable giving: individuals with higher serotonin activity may feel more empathy and thus donate more generously.

• Balanced serotonin supports helpfulness and conflict resolution.
• Low serotonin can reduce prosocial actions due to mood instability.
• Higher serotonin may increase empathy-driven generosity.

While many studies support serotonin’s role in prosocial behaviour, it is important to note that correlation does not prove causation. Other factors like environment and personality also influence behaviour.

Pharmacological studies manipulating serotonin provide stronger evidence but may have ethical and practical limitations.

Additionally, serotonin interacts with other neurotransmitters and hormones, so prosocial behaviour results from complex biological and social processes.

• Correlation between serotonin and prosocial behaviour does not prove causation.
• Experimental manipulation offers stronger evidence but has limits.
• Prosocial behaviour arises from multiple interacting factors.

Oxytocin is a hormone produced primarily in the hypothalamus and released by the pituitary gland. It acts both as a hormone and a neurotransmitter, meaning it can influence cells throughout the body and brain. Oxytocin is often called the 'love hormone' because it is involved in social bonding, maternal behaviours, and forming trust between individuals. Unlike neurotransmitters that act quickly and locally, oxytocin can have longer-lasting effects on behaviour and emotional states.

• Produced in the hypothalamus and released by the pituitary gland.
• Functions as both hormone and neurotransmitter.
• Known for its role in social bonding and reproduction.

Prosocial behaviour refers to actions intended to benefit others, such as helping, sharing, and cooperating. Oxytocin contributes to these behaviours by enhancing feelings of trust, empathy, and connection. For example, when oxytocin levels rise, individuals tend to be more willing to cooperate and less likely to act selfishly. This hormone supports social bonding by making interactions feel rewarding and safe, which encourages people to engage positively with others.

Oxytocin also influences emotional recognition, helping individuals better understand others’ feelings, which is essential for empathy and supportive behaviour.

• Increases trust and cooperation between individuals.
• Enhances empathy by improving emotional recognition.
• Promotes social bonding and reduces fear of social rejection.

Several studies have investigated oxytocin’s effects on human social behaviour. One common method involves administering oxytocin via nasal spray and observing changes in behaviour during social tasks. For example, participants given oxytocin tend to show increased trust in economic games, such as the Trust Game, where they decide how much money to share with strangers.

Other research shows that oxytocin can increase generosity and willingness to help others, even strangers. However, the effects can depend on context and individual differences, such as gender or social background. This suggests oxytocin facilitates prosocial behaviour but does not guarantee it in every situation.

• Oxytocin nasal spray increases trust in experimental games.
• Linked to greater generosity and helping behaviour.
• Effects vary depending on context and individual factors.

Oxytocin is naturally released during positive social interactions, such as hugging, touching, or during childbirth and breastfeeding. For instance, a mother’s oxytocin levels rise during labour, promoting bonding with her newborn. Similarly, friends sharing a warm hug may experience increased oxytocin, strengthening their relationship.

In workplaces, oxytocin may promote teamwork and cooperation by increasing trust among colleagues. Even simple acts like eye contact and smiling can stimulate oxytocin release, encouraging friendly and supportive social environments.

• Released during childbirth and breastfeeding to support mother-infant bonding.
• Increases during physical touch like hugging, promoting social connection.
• Facilitates trust and cooperation in group settings such as workplaces.

While oxytocin plays a significant role in prosocial behaviour, it is not the sole factor. Social behaviours are complex and influenced by multiple biological, psychological, and environmental factors. For example, oxytocin may increase trust towards in-group members but not necessarily towards strangers or out-group individuals.

Additionally, some studies suggest oxytocin can also promote defensive aggression in certain contexts, showing its effects are not always purely positive. Therefore, understanding oxytocin’s role requires considering the broader social and individual context.

• Oxytocin’s effects depend on social context and individual differences.
• May increase trust selectively, favouring in-group members.
• Can sometimes promote defensive or aggressive behaviours.

Prosocial behaviour involves actions intended to benefit others, such as helping, sharing, or comforting. Understanding the brain regions involved helps explain the biological basis of these behaviours. Two key areas are the prefrontal cortex and the amygdala, each playing distinct but complementary roles in social decision-making and emotional processing.

The prefrontal cortex, located at the front of the brain, is essential for complex cognitive functions including decision-making, planning, and impulse control. In the context of prosocial behaviour, it helps individuals evaluate social situations and regulate their responses to act in ways that benefit others rather than acting on selfish impulses.

For example, when deciding whether to donate money to charity, the prefrontal cortex weighs the social benefits and personal costs, enabling a controlled, thoughtful choice rather than an impulsive reaction.

Damage to this area can lead to difficulties in controlling impulses and understanding social norms, which may reduce prosocial actions.

• Regulates decision-making and impulse control.
• Assesses social context to guide behaviour.
• Supports planning and foreseeing consequences of actions.

The amygdala is a small, almond-shaped structure deep within the brain that processes emotions and social signals. It is particularly involved in recognising emotions such as fear and empathy, which are crucial for responding appropriately to others' needs.

For instance, seeing someone in distress activates the amygdala, triggering emotional responses that motivate helping behaviour. This emotional processing helps individuals feel empathy, a key driver of prosocial actions.

If the amygdala is underactive or damaged, a person may struggle to recognise emotional cues, leading to reduced empathy and less prosocial behaviour.

• Processes emotions like fear and empathy.
• Detects social signals important for interaction.
• Influences emotional motivation to help others.

Prosocial behaviour arises from the interaction between the prefrontal cortex and amygdala. While the amygdala generates emotional responses to social stimuli, the prefrontal cortex regulates these emotions and guides appropriate social behaviour.

For example, the amygdala may trigger an emotional urge to help a person in distress, but the prefrontal cortex evaluates the situation and decides the best way to respond, such as offering assistance or calling for help.

This balance ensures that prosocial actions are both emotionally motivated and socially appropriate.

• Amygdala triggers emotional responses to social cues.
• Prefrontal cortex regulates and directs these emotions.
• Together they enable controlled, empathetic prosocial behaviour.

Consider a situation where a person sees someone drop their shopping bags. The amygdala processes the distress or embarrassment of the other person, creating an emotional response. The prefrontal cortex then helps decide to approach and offer help rather than ignore the situation.

Understanding these brain functions can inform approaches in psychology and education to promote prosocial behaviour, such as training emotional recognition or impulse control.

It also highlights why some individuals with brain injuries or disorders affecting these areas may show reduced prosocial tendencies.

• Emotional recognition leads to motivation to help.
• Decision-making guides appropriate helping behaviour.
• Brain function influences social and moral development.

Heritability is a statistical measure used in psychology and genetics to estimate how much of the variation in a particular characteristic or behaviour within a population can be explained by genetic differences. It does not measure the extent to which a trait is genetically determined in an individual, but rather the proportion of variation in a group that is due to genetic factors.

For example, if the heritability of height in a population is 0.8, this means that 80% of the variation in height among individuals in that population is due to genetic differences, while the remaining 20% is due to environmental factors such as nutrition or illness.

• Heritability is expressed as a value between 0 and 1.
• A value of 0 means genetics do not contribute to variation.
• A value of 1 means all variation is due to genetics.

Heritability is often estimated using studies of twins, families, or adopted individuals. For example, comparing similarities in traits between identical (monozygotic) twins, who share nearly 100% of their genes, and fraternal (dizygotic) twins, who share about 50%, helps researchers estimate genetic influence.

The formula for heritability (h²) can be simplified as: h² = Genetic variance / Total phenotypic variance. This means heritability is the proportion of total observed variation in a trait that is due to genetic differences.

It is important to note that heritability applies to populations, not individuals. A high heritability does not mean a trait is fixed or unchangeable in an individual. Environmental factors can still have a significant impact.

• Heritability = Genetic variance ÷ Total variance.
• Twin studies are a common method to estimate heritability.
• Heritability does not predict individual trait outcomes.

Consider intelligence quotient (IQ), which has an estimated heritability of around 0.5 to 0.8 in adults. This suggests that genetic differences explain 50–80% of the variation in IQ scores within a population, while the rest is influenced by environment, education, and life experiences.

In contrast, traits like language spoken or musical ability have lower heritability because they depend heavily on environmental exposure and learning.

For behaviour, prosocial tendencies may show moderate heritability, indicating genetics partly influence how likely someone is to help others, but social context and upbringing also play crucial roles.

• IQ heritability is moderate to high in adults.
• Environmental factors strongly influence learned behaviours.
• Heritability varies by trait and population studied.

Heritability does not imply genetic determinism. A trait with high heritability can still be modified by environmental changes. For example, height is highly heritable, but poor nutrition can stunt growth.

Heritability estimates are specific to the population and environment studied; they can change if environmental conditions change.

It is a common misconception to interpret heritability as the percentage of a trait caused by genes in an individual, which is incorrect. Heritability only applies to variation within a group, not to individuals.

• Heritability is population-specific and environment-dependent.
• High heritability does not mean a trait is unchangeable.
• Avoid interpreting heritability as individual genetic causation.

Understanding heritability helps psychologists separate genetic influences from environmental ones when studying behaviours and traits. This informs research on the biological basis of behaviour and guides interventions.

For example, if prosocial behaviour has moderate heritability, interventions can focus on environmental factors like social learning to encourage helping behaviours.

Heritability estimates also guide genetic research, such as identifying genes associated with certain traits or disorders.

• Heritability informs nature versus nurture debates.
• It guides research and intervention strategies.
• Helps identify genetic contributions to behaviour.

Prosocial behavior includes voluntary actions intended to benefit others, such as helping, sharing, comforting, and cooperating. These behaviours are fundamental to social cohesion and community functioning. Understanding the origins of prosocial behaviour helps psychologists determine whether such actions are innate or learned, which has implications for education and social policy.

For example, a child who shares toys with peers demonstrates prosocial behaviour that may be influenced by both their upbringing and biological predispositions.

• Prosocial behaviour involves actions benefiting others.
• Examples include helping, sharing, and cooperating.
• Studying its origins informs psychological and social understanding.

Heritability refers to the proportion of observed variation in a trait among individuals that can be attributed to genetic differences. It is important to note that heritability does not indicate how much of an individual's behaviour is genetic, but rather how much genetic variation explains differences within a population.

Twin studies are a common method to estimate heritability. By comparing similarities in traits between monozygotic (MZ) twins, who share nearly 100% of their genes, and dizygotic (DZ) twins, who share about 50%, researchers infer the genetic contribution to behaviours.

For example, if MZ twins show more similar levels of prosocial behaviour than DZ twins, this suggests a genetic influence.

• Heritability measures genetic contribution to trait variation.
• Twin studies compare MZ and DZ twins to estimate heritability.
• Greater similarity in MZ twins implies genetic influence.

Monozygotic twins develop from a single fertilised egg that splits, resulting in two individuals with identical genetic material. Dizygotic twins develop from two separate eggs fertilised by different sperm, sharing on average 50% of their segregating genes, similar to regular siblings.

This genetic difference is crucial for behavioural genetics research. If a trait is strongly influenced by genetics, MZ twins should be more alike in that trait than DZ twins.

For example, if prosocial behaviour scores are more closely matched in MZ twins than DZ twins, this supports a genetic component.

• MZ twins share 100% of genes; DZ twins share ~50%.
• Greater behavioural similarity in MZ twins suggests genetic influence.
• Twin type comparison is key to heritability studies.

Research consistently finds that MZ twins exhibit higher concordance rates for prosocial behaviours than DZ twins. This means that identical twins tend to be more similar in their willingness to help, share, or cooperate than fraternal twins.

For instance, a study might measure prosocial tendencies through questionnaires or observed behaviour and find correlations of 0.6 for MZ twins and 0.3 for DZ twins. The higher correlation in MZ twins indicates a genetic influence.

However, these studies also show that environmental factors contribute significantly, as MZ twins are not perfectly concordant. Shared family environment and unique experiences also shape prosocial behaviour.

• MZ twins show greater similarity in prosocial behaviour than DZ twins.
• Correlations in prosocial traits are higher for MZ twins (e.g., 0.6) than DZ twins (e.g., 0.3).
• Environmental factors also play a significant role.

While twin studies highlight a genetic component, prosocial behaviour is not determined by genes alone. Environmental influences such as parenting style, cultural norms, peer groups, and life experiences interact with genetic predispositions.

For example, two MZ twins raised in different environments may develop different levels of prosocial behaviour despite identical genetics. Conversely, DZ twins raised together may show similarities due to shared environment.

This interaction suggests that prosocial behaviour arises from complex gene-environment interplay rather than simple genetic determinism.

• Genes contribute but do not solely determine prosocial behaviour.
• Environmental factors like upbringing and culture are influential.
• Gene-environment interaction shapes prosocial tendencies.

Prosocial behaviour involves voluntary actions intended to help or benefit others, such as sharing, comforting, or cooperating. The biological explanation suggests that these behaviours are influenced by genetic factors inherited from our parents, meaning some individuals may be naturally more inclined to act in helpful ways due to their biological makeup.

This perspective contrasts with explanations that focus solely on environmental or social learning influences, highlighting the role of innate predispositions in shaping prosocial tendencies.

• Prosocial behaviour benefits others.
• Biological explanation focuses on inherited genetic influences.
• Innate predispositions may affect helping behaviours.

Heritability is a statistical estimate that indicates the proportion of variation in a trait within a population that can be attributed to genetic differences. It does not refer to how much of an individual's behaviour is genetic, but rather how much genetics contribute to differences between people.

For example, if social responsibility has a high heritability, this means that genetic differences explain a significant part of why some people are more socially responsible than others. However, environmental factors also play a role and heritability can vary depending on the population and context.

• Heritability measures genetic contribution to trait variation.
• It applies to populations, not individuals.
• Both genes and environment influence behaviour.

Rushton conducted research using twin studies to investigate the genetic basis of social responsibility, a key aspect of prosocial behaviour. By comparing identical (monozygotic) twins, who share nearly all their genes, with fraternal (dizygotic) twins, who share about half, he assessed how much genetics contribute to social responsibility.

The study found that identical twins showed more similarity in social responsibility than fraternal twins, suggesting a genetic influence. This supports the idea that prosocial behaviours like social responsibility have a heritable component.

For example, if one identical twin is highly socially responsible, the other is more likely to be similar compared to fraternal twins.

• Twin studies compare identical and fraternal twins.
• Greater similarity in identical twins suggests genetic influence.
• Rushton's findings support heritability of social responsibility.

If prosocial behaviour is partly inherited, this means some people may be naturally more inclined to help others. For instance, a person with a genetic predisposition towards empathy might be more likely to volunteer or comfort friends in distress.

This biological influence does not mean behaviour is fixed; environmental factors such as upbringing and culture also shape prosocial actions. However, recognising genetic contributions helps explain individual differences in helping behaviour.

Understanding this can inform approaches in education or social policy by acknowledging innate tendencies alongside social learning.

• Genetic predispositions influence likelihood of helping.
• Behaviour is shaped by both genes and environment.
• Recognising biology aids understanding of individual differences.

The biological explanation for prosocial behaviour, supported by Rushton's heritability study, provides evidence that genetics contribute to social responsibility and helping behaviours. This perspective highlights inherited traits as one factor influencing prosocial actions.

However, it is important to consider that heritability estimates do not imply determinism; environmental and situational factors also play crucial roles. Additionally, twin studies have limitations such as shared environments that can confound results.

Overall, the biological explanation complements other approaches by emphasising the role of genetic factors in prosocial behaviour.

• Genetics contribute to prosocial behaviour but do not determine it.
• Environmental influences remain important.
• Rushton's study supports but does not fully explain prosocial behaviour.

Biological explanations often attribute prosocial behavior to genetic inheritance, brain structures, or neurochemical processes such as serotonin or oxytocin activity. While these factors provide a foundation for understanding innate tendencies, they do not fully account for the variability in prosocial actions observed across different contexts and cultures.

For example, two individuals with similar genetic predispositions may behave differently depending on their upbringing or social environment. This suggests that biology alone cannot explain why people help others in some situations but not in others.

Moreover, biological explanations sometimes overlook the complexity of human social interactions and the role of learning and experience in shaping behaviour. Therefore, it is important to consider environmental influences alongside biological factors.

• Biological explanations focus on innate predispositions.
• They may not explain situational variability in helping behaviour.
• They often neglect the role of learning and social context.

Social groups, including family, peers, and wider cultural communities, provide norms and expectations that guide behaviour. These norms can encourage or discourage prosocial actions depending on the values promoted within the group.

For instance, in collectivist cultures, helping others and prioritising group welfare is often emphasised, leading to higher rates of prosocial behaviour within those communities. Conversely, individualistic cultures may stress personal achievement, which can influence the frequency and type of helping behaviours.

Peer groups especially during adolescence can strongly influence prosocial behaviour. If a peer group values cooperation and kindness, individuals are more likely to engage in helping behaviours to gain acceptance and approval.

• Cultural norms shape expectations about helping others.
• Collectivist cultures often promote more prosocial behaviour than individualistic ones.
• Peer groups can reinforce or inhibit prosocial actions.

Social roles, such as being a student, parent, or team member, come with behavioural expectations that can promote prosocial actions. For example, a teacher is expected to support and help students, which encourages prosocial behaviour within that role.

Situational factors also influence whether people act prosocially. In emergencies, the presence of others can lead to diffusion of responsibility, reducing helping behaviour (bystander effect). However, in smaller or more familiar groups, individuals may feel more responsible and thus more likely to help.

These examples show that prosocial behaviour is flexible and responsive to social context rather than fixed by biology alone.

• Social roles carry expectations that encourage helping behaviour.
• Situational factors like group size affect likelihood of helping.
• Prosocial behaviour adapts to social context and role demands.

Prosocial behaviour is often learned through observation and reinforcement within families and communities. Children who observe parents or caregivers acting kindly and helping others are more likely to imitate these behaviours.

Educational settings also play a role by teaching values such as empathy, sharing, and cooperation. These learned behaviours can become internalised and guide future prosocial actions.

This learning perspective highlights that prosocial behaviour is not purely innate but develops through interaction with the environment.

• Children learn prosocial behaviour by observing role models.
• Schools teach social values that promote helping.
• Learning shapes prosocial tendencies over time.

While environmental factors strongly influence prosocial behaviour, they often interact with biological predispositions. For example, a person with a genetic tendency towards empathy may be more receptive to socialisation that encourages helping.

Similarly, neurochemical systems like oxytocin may facilitate bonding and trust, but the expression of prosocial behaviour depends on social context and learned norms.

Understanding prosocial behaviour requires recognising this complex interplay rather than attributing it solely to biology or environment.

• Biological predispositions can enhance sensitivity to social influences.
• Neurochemicals support social bonding but do not determine behaviour alone.
• Prosocial behaviour results from dynamic interaction of biology and environment.

Prosocial behaviour refers to voluntary actions intended to benefit others, such as helping, sharing, or comforting. The biological explanation suggests that innate physiological and genetic factors contribute to why individuals engage in such behaviours. Understanding these biological mechanisms allows us to predict and explain prosocial actions beyond familiar examples, by recognising how internal processes promote cooperation and empathy.

• Prosocial behaviour benefits others and society.
• Biological factors include genetics, neurotransmitters, hormones, and brain structures.
• These factors can predispose individuals to act altruistically.

Neurotransmitters are chemical messengers released by nerve cells to communicate with target cells. Two key chemicals linked to prosocial behaviour are serotonin and oxytocin. Serotonin influences mood and social behaviour; higher serotonin levels are associated with increased cooperation and reduced aggression. Oxytocin, often called the 'bonding hormone', enhances trust, empathy, and social bonding, making individuals more likely to help others.

For example, after receiving oxytocin via nasal spray in controlled studies, participants tend to show more generosity in economic games. This demonstrates how chemical changes in the brain can directly affect prosocial decisions.

• Serotonin regulates mood and promotes cooperative behaviour.
• Oxytocin increases trust and empathy, facilitating helping actions.
• Changes in these chemicals can alter likelihood of prosocial acts.

Genetic predispositions also contribute to prosocial tendencies. Twin studies compare identical (monozygotic) and fraternal (dizygotic) twins to estimate heritability — the proportion of behavioural variation due to genetics. Higher similarity in prosocial behaviour among identical twins suggests a genetic component.

For instance, if identical twins raised apart both show similar levels of social responsibility, this supports a biological basis. However, genes interact with environment, so genetics alone do not determine behaviour.

• Heritability estimates show genetic contribution to prosocial traits.
• Twin studies provide evidence for genetic influence.
• Genes set predispositions, but environment shapes expression.

Certain brain areas regulate emotions and decision-making linked to prosocial acts. The prefrontal cortex is involved in planning and impulse control, enabling thoughtful helping behaviour. The amygdala processes emotions like fear and empathy, influencing responses to others' distress.

Damage to these areas can reduce prosocial tendencies, illustrating their role. For example, individuals with impaired prefrontal cortex function may struggle to inhibit selfish impulses, decreasing helpful actions.

• Prefrontal cortex supports planning and self-control in helping.
• Amygdala processes emotional cues important for empathy.
• Brain damage studies highlight these regions' roles.

When encountering unfamiliar scenarios involving prosocial behaviour, consider how biological factors might influence responses. For example, in a stressful emergency, elevated oxytocin could increase helping by enhancing trust among strangers. Alternatively, genetic predispositions might explain why some individuals consistently volunteer in community service.

By analysing the roles of neurotransmitters, hormones, genetics, and brain function, we can predict or explain prosocial actions even in novel contexts, such as cross-cultural differences or unusual social settings.

• Use knowledge of biological mechanisms to interpret new prosocial behaviours.
• Consider chemical, genetic, and brain influences in context.
• Predict behaviour by linking biological factors to observed actions.