Paper 1 Psychology Study Critical Thinking

Neurotransmitters - Acetylcholine and Seretonin (5HTT)

1. Neurotransmitters: Acetylcholine and Serotonin Acetylcholine (ACh)

• Chemical nature: Acetylcholine is a neurotransmitter synthesized in nerve terminals from choline and acetyl-CoA by the enzyme choline acetyltransferase.

• Function:

  • Primary role in learning and memory, especially in the hippocampus and cerebral cortex.

  • Also involved in muscle activation by acting at neuromuscular junctions.

• Receptors:

  • Two main types: nicotinic (ionotropic) and muscarinic (metabotropic) receptors.

  • Scopolamine acts as a muscarinic receptor antagonist, blocking ACh binding.

• Mechanism:

  • After release into the synaptic cleft, acetylcholine binds to its receptors on the postsynaptic neuron to propagate nerve impulses.

  • Involved in long-term potentiation (LTP), a key process in strengthening synaptic connections during learning.

• Deactivation:

  • Broken down by acetylcholinesterase to terminate the signal.

• Relevance to behavior:

  • Essential for spatial memory and episodic memory.

  • Deficits linked to memory disorders like Alzheimer’s disease.

Serotonin (5-HT)

• Chemical nature: Serotonin is a monoamine neurotransmitter synthesized from the amino acid tryptophan.

• Function:

  • Regulates mood, anxiety, sleep, appetite, and cognition.

  • Influences emotional states and social behavior.

• Receptors:

  • Multiple receptor types (5-HT1, 5-HT2, etc.) with different effects.

• Synaptic function:

  • After release, serotonin acts on postsynaptic receptors.

  • Reuptake of serotonin from the synaptic cleft back into the presynaptic neuron is mediated by the serotonin transporter protein (5-HTT).

• Reuptake:

  • The 5HTT gene (SLC6A4) codes for this transporter.

  • SSRIs (selective serotonin reuptake inhibitors) block this transporter, increasing serotonin availability.

• Relevance to behavior:

  • Abnormal serotonin signaling is linked to depression, anxiety disorders, and aggression.

  • Serotonin’s modulation of emotional responses is crucial for mental health.

2. The 5HTT Gene (Serotonin Transporter Gene)

• Location: On chromosome 17.

• Polymorphism: The gene has a well-studied variable number tandem repeat (VNTR) polymorphism in its promoter region called 5-HTTLPR (serotonin-transporter-linked polymorphic region).

• Alleles:

  • Short (s) allele: 14 repeats, results in lower transcription efficiency → fewer transporter proteins → less reuptake → higher serotonin availability but paradoxically linked to greater vulnerability to stress.

  • Long (l) allele: 16 repeats, higher transcription → more transporter → more reuptake → reduced serotonin in synapse.

• Mechanism of influence:

  • The short allele is thought to alter serotonergic signaling pathways, increasing emotional reactivity to stress and environmental factors.

  • Acts as a moderator in gene-environment interactions, influencing susceptibility to depression and anxiety.

• Research importance:

  • Provides a biological basis for individual differences in emotional regulation.

  • Helps explain why not all individuals exposed to stress develop mental health disorders.

Neurotransmitters - Understanding

Integrative Understanding and Theoretical Implications

• Antonova et al. (2011) shows how acetylcholine neurotransmission is necessary for cognitive processes like memory, demonstrating neurotransmitters’ direct role in brain function and behavior.

• Caspi et al. (2003) shows how a serotonin-related gene interacts with environment to influence emotional behavior, highlighting gene-environment interplay rather than a simple genetic determinism.

• Both studies emphasize biological underpinnings of psychological phenomena but in different domains: cognition (memory) vs. emotion (depression).

• These findings support the biological level of analysis in psychology by linking neurotransmitters and genes to observable behaviors and mental processes.

• Provide evidence for biopsychosocial models explaining behavior through interactions among biology, environment, and psychological factors.

Neuroplasticity - K+U

1. What is Neuroplasticity?

• Neuroplasticity is the brain’s ability to change and adapt physically and functionally throughout life.

• These changes happen when people learn new skills, have new experiences, or after brain injury.

2. Types of Brain Changes

• Structural changes: Physical changes in the brain’s size, shape, or volume, especially in areas related to learning.

• Functional changes: Changes in how brain areas work or communicate without visible physical changes.

3. Experience-Dependent Plasticity

• The brain changes in response to experiences and learning.

• Repeated practice of a skill or exposure to an environment causes brain areas related to that skill to grow or reorganize.

4. Localization of Function

• Different brain areas control different abilities (e.g., the hippocampus helps with spatial memory).

• Neuroplastic changes happen mainly in the brain parts that relate directly to the new skill or experience.

5. Use and Disuse

• Brain areas used frequently become stronger and larger.

• If a skill or brain function isn’t used, those areas may shrink or become less active.

6. Neuroplasticity Throughout Life

• Neuroplasticity occurs not only in childhood but also in adulthood.

• The brain can continue to learn and adapt new skills at any age.

7. How Do Scientists Measure Neuroplasticity?

• Scientists use brain scanning tools like MRI to see changes in brain structure over time.

• MRI helps show increases or decreases in brain volume after learning or experience.

Neuroplasticity - Understanding

Maguire (1999) — London Taxi Drivers

• Neuroplasticity: Maguire showed that learning and practicing complex spatial navigation led to physical changes in the hippocampus.

• Localization of Function: The hippocampus, which is important for spatial memory, was larger in taxi drivers.

• Use and Disuse: The longer someone worked as a taxi driver, the bigger their hippocampus, showing use-dependent growth.

• Measurement: MRI scans provided clear evidence of these brain changes.

Draganski et al. (2004) — Learning to Juggle

• Neuroplasticity: Draganski showed that learning a new motor skill like juggling caused the brain to grow in specific areas.

• Localization of Function: Increases were found in brain areas related to visual and motor skills.

• Use and Disuse: After stopping juggling, these brain changes decreased, showing how plasticity can be reversible.

• Measurement: MRI scans tracked these changes over time.

LOF - K+U

1. What is Localization of Function?

• Localization of Function means that specific areas of the brain control specific behaviors or cognitive functions.

• The brain is organized such that different regions have specialized roles.

2. Role of the Hippocampus

• The hippocampus, located in the medial temporal lobe, is crucial for memory formation, particularly episodic memory and spatial memory/navigation.

• It helps form cognitive maps that allow an individual to navigate and remember environments.

3. Hippocampus and Spatial Memory

• The hippocampus enables spatial orientation by encoding and retrieving information about the environment.

• Damage to the hippocampus can impair one’s ability to form new memories or navigate spatial environments.

4. Structural and Functional Specificity

• The posterior hippocampus is particularly involved in spatial navigation.

• Different parts of the hippocampus may have different functional roles.

• Activity in the hippocampus increases when individuals engage in tasks requiring spatial memory.

5. Measuring Hippocampal Function

• MRI scans can detect structural changes in the hippocampus.

• Functional MRI (fMRI) can show hippocampal activation during spatial tasks.

• Behavioral tests on navigation ability can be correlated with hippocampal structure and activity.

LOF - Understanding 

Maguire (1999) — London Taxi Drivers

• LOF: Maguire found that the posterior hippocampus was larger in taxi drivers, showing that this area is specialized for spatial navigation.

• The longer someone spent as a taxi driver, the larger their posterior hippocampus, supporting the idea that this brain region adapts based on spatial memory demands.

• This provides strong evidence for the hippocampus’s role in spatial memory and navigation.

Antonova et al. (2011) — Virtual Morris Water Maze and Hippocampal Activation

• LOF: Antonova used fMRI to show that the hippocampus is actively involved during spatial navigation tasks.

• Participants navigated a virtual environment while their hippocampal activity was measured.

• The study demonstrated that disrupting hippocampal function with transcranial magnetic stimulation (TMS) impaired spatial memory performance.

• This confirms the hippocampus’s specific and necessary role in spatial memory and navigation.

BIT - K+U

1. What is MRI?

• Magnetic Resonance Imaging (MRI) is a non-invasive brain scanning technique.

• It uses strong magnetic fields and radio waves to create detailed images of the brain’s structure.

• MRI produces high-resolution 3D images showing differences in brain tissue types (e.g., gray matter vs. white matter).

2. How Does MRI Work?

• MRI detects changes in the magnetic properties of hydrogen atoms in water molecules in the brain.

• When placed in a magnetic field, hydrogen atoms align and then emit signals when disturbed by radio waves.

• These signals are processed by a computer to generate detailed images of the brain’s anatomy.

3. Advantages of MRI

• Provides clear, detailed images of brain structures.

• Non-invasive and does not use harmful radiation (unlike CT scans or X-rays).

• Useful for studying brain anatomy and detecting structural changes over time.

• Can measure volume differences in specific brain regions.

4. Limitations of MRI

• MRI shows structure but not brain activity (unlike fMRI).

• It can be expensive and time-consuming.

• Participants must stay very still, which can be difficult for some.

• It can only infer function from structure, so caution is needed when linking brain size to behavior.

5. MRI in Studying Neuroplasticity

• MRI allows researchers to detect structural brain changes due to experience or learning.

• It can measure gray matter volume changes in specific brain regions.

• This makes MRI a key tool for studying neuroplasticity in living humans.

BIT - Understanding

Maguire (1999) — London Taxi Drivers

• MRI use: Maguire used MRI scans to compare the hippocampal volume of taxi drivers with non-taxi drivers.

• The scans showed that taxi drivers had larger posterior hippocampi, linking brain structure with their extensive spatial navigation experience.

• MRI allowed for precise measurement of brain structures, providing evidence of experience-dependent neuroplasticity.

Draganski et al. (2004) — Learning to Juggle

• MRI use: Draganski used MRI scans before, during, and after juggling training to detect changes in brain gray matter.

• The scans showed increased gray matter in areas related to visual and motor processing after learning juggling.

• MRI provided clear evidence of structural brain changes linked to learning a new skill, demonstrating neuroplasticity.

Hormones - K+U

1. What are Hormones?

• Hormones are chemical messengers released by endocrine glands into the bloodstream.

• They regulate various bodily functions including mood, stress response, growth, and behavior.

• Hormones can influence brain function and behavior by binding to receptors in the brain.

2. Cortisol

• Cortisol is a stress hormone produced by the adrenal glands as part of the body’s response to stress.

• It plays a key role in the “fight or flight” response, helping the body manage acute stress.

• While short-term cortisol release helps adaptation, chronic high levels of cortisol can impair brain function, particularly memory.

• Cortisol affects the hippocampus, which is sensitive to prolonged stress and high cortisol, potentially leading to memory deficits.

3. Testosterone

• Testosterone is a steroid hormone primarily produced in the testes (in males) and ovaries (in females), with small amounts from the adrenal glands.

• It influences male secondary sexual characteristics and has been linked to aggressive and dominant behavior.

• Testosterone can affect brain areas related to aggression, dominance, and social behavior, such as the amygdala.

• Higher testosterone levels have been associated with increased aggression and risk-taking, but the relationship is complex and influenced by social context.

4. Measuring Hormones

• Hormone levels are commonly measured using saliva or blood samples.

• These measurements allow researchers to correlate hormone levels with behavioral or cognitive changes.

Hormones - Understanding 

Newcomer et al. (1999) — Cortisol and Memory

• Hormone focus: Newcomer et al. studied the effect of cortisol on verbal declarative memory.

• Participants were given high or low doses of cortisol or a placebo over several days.

• The study showed that high cortisol levels impaired memory performance, supporting the idea that chronic cortisol negatively affects hippocampal function.

• This provides evidence of how a hormone like cortisol can influence cognitive processes such as memory.

Dabbs et al. (1995) — Testosterone and Behavior

• Hormone focus: Dabbs et al. measured testosterone levels in male prisoners.

• They found that higher testosterone levels were linked to more aggressive and violent behavior.

• This supports the understanding that testosterone influences social and aggressive behaviors.

• The study illustrates the hormone’s role in modulating behavior linked to dominance and aggression.

Pheromones - K+U

1. What are Pheromones?

• Pheromones are chemical substances released by an individual that can affect the behavior or physiology of others of the same species.

• In humans, the role of pheromones is debated, but some research suggests they can influence social and sexual behavior.

• Unlike hormones, which are released inside the body to regulate internal processes, pheromones are released outside the body to send signals to others.

2. AND (Androstadienone)

• AND is a chemical found in male sweat and is considered a putative human pheromone.

• It is linked to influencing mood, attention, and physiological arousal in women.

• Exposure to AND has been suggested to affect women’s perception of men and can influence brain activity related to emotional processing.

3. EST (Estratetraenol)

• EST is a chemical found in female secretions, considered a possible human pheromone.

• It may influence men’s mood and perception of women, potentially affecting attraction or social cognition.

• EST is less studied than AND but is believed to have some role in social signaling between sexes.

4. Measuring the Effects of Pheromones

• Researchers often expose participants to AND or EST and measure changes in behavior, mood, or brain activity.

• Effects can include changes in mood ratings, attractiveness judgments, or physiological responses like skin conductance.

Pheromones - Understanding

Lundstrom and Olsson (2005) — AND and Mood in Women

• Pheromone focus: Lundstrom and Olsson investigated how AND affected women’s mood.

• They exposed women to AND and found that it enhanced mood, but only when women thought a male experimenter was present.

• This suggests AND influences social and emotional processing, supporting the idea that pheromones affect human behavior in subtle ways.

• The study highlights the interaction between chemical signals and social context.

Hare et al. (2017) — AND and EST and Attraction

• Pheromone focus: Hare et al. tested whether AND and EST influenced human mate selection and attraction.

• They found no evidence that exposure to these chemicals affected sexual attraction or judgments of attractiveness.

• Their results challenged earlier claims about human pheromones, suggesting that AND and EST may not function as human pheromones in mate choice.

• This study illustrates the ongoing debate and the complexity of studying pheromones in humans.

Genes and Behaviour - K+U

1. What Are Genes?

• Genes are units of heredity made of DNA that influence physical and behavioral traits.

• They can affect brain function and behavior by influencing the production of proteins and neurotransmitters.

• Behavioral genetics studies how genes and environment interact to shape behavior.

2. 5-HTT Gene (Serotonin Transporter Gene)

• The 5-HTT gene controls the production of the serotonin transporter protein, which regulates serotonin levels in the brain.

• Serotonin is a neurotransmitter involved in mood regulation.

• Variations in the 5-HTT gene, especially the short allele (s) versus the long allele (l), are linked to differences in vulnerability to depression, especially after stressful life events.

• The short allele is associated with less efficient serotonin transport and higher risk of depression under stress.

3. MAOA Gene (Monoamine Oxidase A)

• The MAOA gene produces the enzyme monoamine oxidase A, which breaks down neurotransmitters like serotonin, dopamine, and norepinephrine.

• Variations in MAOA activity affect levels of these neurotransmitters in the brain.

• The low-activity MAOA variant has been linked to increased aggressive and antisocial behavior, especially when combined with environmental factors like childhood maltreatment.

• This gene is sometimes called the “warrior gene” due to its association with aggression.

4. Gene-Environment Interaction

• Both genes demonstrate that behavior results from an interaction between genetic predispositions and environmental influences.

• Carrying a particular gene variant does not guarantee a behavior but may increase susceptibility when combined with certain experiences.

Genes and Behaviour - Understanding 

Caspi et al. (2003) — 5-HTT Gene and Depression

• Gene studied: 5-HTT gene (serotonin transporter).

• Caspi et al. found that individuals with the short allele of 5-HTT were more likely to develop depression after stressful life events than those with the long allele.

• This study demonstrated a gene-environment interaction: the gene alone did not predict depression, but in combination with stress, it increased risk.

• It highlights how genetic vulnerability interacts with environmental stressors in shaping behavior.

Caspi et al. (2002) — MAOA Gene and Aggression

• Gene studied: MAOA gene.

• Caspi et al. found that males with the low-activity MAOA variant were more likely to develop aggressive or antisocial behavior if they experienced childhood maltreatment.

• Again, this is an example of gene-environment interaction, where the gene affects behavior primarily under certain environmental conditions.

• The study supports the idea that genetics can influence predispositions but are not deterministic.

Genetic Similarities - K+U

1. What Are Twin and Kinship Studies?

• Twin studies compare monozygotic (MZ) twins, who share 100% of their genes, to dizygotic (DZ) twins, who share about 50%.

• Kinship studies examine genetic similarities between family members of varying degrees (e.g., siblings, parents, cousins).

• These studies aim to estimate the heritability of traits by assessing how much genetics contribute to similarities in behavior or disorders.

2. Heritability

• Heritability is the proportion of observed variation in a trait among individuals that can be attributed to genetic differences.

• Higher concordance rates for a trait in MZ twins compared to DZ twins suggest a stronger genetic influence.

3. Environmental Influences

• While genetics play a role, environment also affects behavior.

• Twin and kinship studies also try to separate genetic effects from shared and non-shared environmental influences.

4. Limitations

• Equal environment assumption: Assumes MZ and DZ twins experience similar environments, which may not always be true.

• Generalizability: Twins may not represent the general population.

• Interaction between genes and environment complicates conclusions.

Genetic Similarities - Understanding

Kendler et al. (2006) — Twin Study on Major Depression

• Focus: Examined genetic and environmental contributions to major depression in Swedish twins.

• Found higher concordance rates for depression in MZ twins than DZ twins, indicating a significant genetic component.

• The study estimated heritability of depression to be about 38%, showing genetics play a moderate role.

• Environmental factors also contributed, showing that depression results from both genetic and environmental influences.

Weissman et al. (2005) — Kinship Study on Depression Across Generations

• Focus: Studied depression across three generations of families to examine genetic transmission.

• Found that the risk of depression was higher in children and grandchildren if the parent/grandparent had depression.

• This supports the idea of genetic transmission of vulnerability to depression.

• The study also emphasized environmental factors within families influencing depression.

Evolutionary Explanations - K+U 

1. What is Disgust?

• Disgust is a basic human emotion that evolved to protect individuals from disease and contamination.

• It involves a strong feeling of revulsion towards things that may carry pathogens or harmful substances.

• Disgust triggers behaviors that help avoid infection, such as avoiding spoiled food or bodily fluids.

2. Evolutionary Function of Disgust

• Disgust evolved as a behavioral immune system to increase chances of survival by reducing contact with disease-causing agents.

• The emotion helps humans avoid pathogens in the environment, especially through food selection and social behavior.

• Disgust sensitivity may vary depending on factors like pregnancy or immune system vulnerability, enhancing protection when it is most needed.

3. Disgust and Pregnancy

• Pregnant women may experience heightened disgust sensitivity to protect the developing fetus from harmful pathogens.

• This adaptive mechanism is important since a compromised immune system during pregnancy increases vulnerability to infections.

4. Measuring Disgust

• Disgust sensitivity can be measured through self-reports or behavioral responses to potentially disgusting stimuli.

• Researchers may assess how factors like pregnancy or hormonal changes affect disgust reactions.

Evolutionary Explanations - Understanding

Fessler (2005) — Disgust Sensitivity in Pregnant Women

• Evolutionary focus: Fessler investigated whether pregnant women have increased disgust sensitivity.

• The study found that first-trimester pregnant women reported higher disgust levels, especially to food-related stimuli.

• This supports the evolutionary explanation that disgust helps protect the fetus by avoiding potential sources of infection during a vulnerable period.

• The study highlights the adaptive nature of disgust in response to biological needs.

Curtis et al. (2004) — Disgust Responses to Disease Cues

• Evolutionary focus: Curtis et al. examined disgust reactions to images depicting potential disease threats (e.g., rotten food, bodily waste).

• Participants consistently rated these images as highly disgusting, across cultures.

• Disgust was strongest for stimuli linked to potential pathogens, supporting the idea that disgust evolved to avoid disease.

• The study provided cross-cultural evidence for the evolutionary basis of disgust as a protective mechanism.

Importance of Animal Research

1. Why Animal Research is Used

• Animal research allows scientists to study biological and psychological processes that are difficult or unethical to examine in humans.

• It provides a controlled environment to explore brain-behavior relationships, genetics, neurochemistry, and learning.

• Many animals share similar physiological and neurological systems with humans, making them useful models.

2. Ethical Considerations

• Animal research raises ethical concerns about the welfare of animals.

• Strict guidelines regulate the care and use of animals in research to minimize harm.

• The benefits to human knowledge and health must outweigh the potential harm to animals.

3. Contributions to Understanding Behavior

• Animal studies have been crucial for understanding fundamental psychological processes such as classical and operant conditioning.

• They provide insight into the biological basis of behavior, including genetics, neuroplasticity, and the effects of neurotransmitters.

• Studies on animals have led to advances in treatments for mental health disorders.

4. Advantages of Animal Research

• Control of variables: Researchers can manipulate variables that would be impossible or unethical in humans.

• Shorter life cycles: Some animals reproduce quickly, allowing study of genetics across generations.

• Invasive techniques: Procedures like brain lesions or genetic modification can be done on animals but not on humans.

5. Limitations and Generalizability

• Findings from animals may not always translate directly to humans due to species differences.

• Ethical issues continue to be debated in the use of animals in research.

6. Examples from IB Psychology

• Studies on rats and monkeys have illuminated learning processes.

• Research on mice and fruit flies has advanced understanding of genetics.

• Animal models have contributed to knowledge of neuroplasticity and brain localization.

Use of Animal Models

Use of different types of animals

1. Rats

• Commonly used in studies of learning, memory, and neuroplasticity.

• Their brain structure shares similarities with humans, particularly in areas like the hippocampus.

• Advantages:

  • Easy to handle and breed.

  • Well-mapped brain anatomy.

  • Useful for controlled experiments on brain damage and behavior.

• Example use:

  • Studies on spatial memory using mazes.

  • Research on brain plasticity after lesions or environmental enrichment.

2. Mice

• Similar to rats but smaller and faster breeding.

• Used extensively in genetic and behavioral research.

• Advantages:

  • Well-studied genetics.

  • Rapid reproduction allows study of multiple generations.

• Example use:

  • Behavioral tests like the Morris water maze for memory.

3. Genetically Altered Mice (Knockout and Transgenic Mice)

• Mice with specific genes added, removed, or modified.

• Used to study the role of specific genes in behavior and brain function.

• Advantages:

  • Can isolate effects of single genes.

  • Help understand genetic contributions to disorders like depression, anxiety, or Alzheimer’s.

• Example use:

  • Knockout mice lacking a gene linked to serotonin transporters to study depression-like behaviors.

  • Transgenic mice with Alzheimer’s-related genes to study disease progression.

4. Rhesus Monkeys (Macaca mulatta)

• Non-human primates with close genetic, anatomical, and behavioral similarity to humans.

• Used to study complex cognitive functions, social behavior, and neurobiology.

• Advantages:

  • More accurate models for human brain and behavior.

  • Can perform complex tasks and social interactions.

• Limitations:

  • Ethical concerns due to cognitive complexity.

  • More expensive and time-consuming to study.

• Example use:

  • Studies on memory and learning.

  • Research on social bonding and effects of maternal separation.

Animal Ethics

• There are particular ethical guidelines which apply only to the use of animals as set down by bodies such as the British Psychological Society (BPS) and the American Psychological Association (APA)

• In the past animals may have been used without much consideration for their wellbeing but it is becoming increasingly important that researchers exercise due care and respect for their animal subjects to minimise suffering and only use animal subjects when it is deemed necessary

• Researchers must undertake a cost/benefit analysis when considering using animals in research: if the costs outweigh the benefits then the research should not take place

• Any study which uses animals should have a clear aim and should be able to stand up to scrutiny as a piece of scientific research

• Possible alternatives to the use of animals in research include using cell cultures, computer simulations or conducting a meta-analysis i.e. using work already completed by other researchers

• There are three clear determining factors which researchers must apply when using animals in research: Replace; Reduce; Refine

• Replace: use alternatives to live animals e.g. computer simulations or existing video footage of previous research

• Reduce: use as few animals as possible for the study and conduct a pilot study to ensure that any flaws in the procedure are addressed so that animals are not used thoughtlessly

• Refine: procedures must be analysed to ensure that animals do not suffer unnecessarily e.g. limit any aversive or harmful elements to the procedure such as keeping an animal in isolation or interfering with its usual routines such as feeding and sleeping; avoid overcrowding animals in laboratory cages

• Refine: study animals in the wild, living in their natural environment where possible; handle animals with care, particularly if the animal has undergone any surgery as part of the research process

Animals related to Brain and Behaviour

Animal research plays a critical role in advancing our understanding of the biological foundations of behaviour. Specifically, it allows psychologists to explore how brain structures, neurotransmitters, and environmental influences interact to shape behaviour. Because many biological systems—especially in mammals—are evolutionarily conserved, findings from animal models can often be meaningfully applied to human psychology.

Here are the key reasons animal models are essential in studying brain and behaviour:

1. Neurobiological Similarity

• Mammals such as rats and rhesus monkeys share many structural and functional features with the human brain, including regions like the hippocampus and neurotransmitter systems like acetylcholine, dopamine, and serotonin.

• This similarity allows researchers to study complex processes such as memory, learning, and neuroplasticity in a way that can help inform human psychological theory.

2. Experimental Control and Invasive Procedures

• Animal models enable researchers to conduct invasive procedures (e.g. brain lesioning, dissection, or intracranial drug injections) that would be unethical or impossible in human participants.

• These procedures allow for greater experimental control, enabling clear cause-and-effect conclusions about how specific biological variables influence behaviour.

3. Insight into Brain-Behaviour Relationships

• Animal research has been foundational in identifying localization of function (e.g. the hippocampus and memory) and understanding how external factors such as enriched or deprived environments can lead to structural brain changes (i.e. neuroplasticity).

• It supports the biological approach to behaviour by providing empirical evidence of how internal biological systems directly impact observable actions and mental processes.

4. Ethical Considerations

• While animal research is strictly regulated to minimize harm, its use is often justified when the potential benefits (e.g. developing treatments for neurological or psychological disorders) are significant.

• Animals offer an ethical and practical alternative for testing hypotheses that would otherwise not be possible in human research.

Animals - Hormones and Pheromones

In animal research, hormones and pheromones are studied to understand how internal chemical messengers influence observable behaviours such as aggression, stress responses, and social bonding. Animal models — particularly mammals like rats — are used because they:

• Share evolutionarily conserved hormonal systems with humans.

• Allow for invasive procedures (e.g. castration, hormone injections) and precise environmental control, which would be unethical in human studies.

• Enable the study of long-term developmental changes across generations.

Hormones in Animals

• Hormones are chemical messengers secreted by endocrine glands into the bloodstream. In animals, hormones regulate social behaviours, such as dominance, maternal care, reproduction, and defence.

• Key hormones studied in animal models:

  • Cortisol (or corticosterone in rodents): regulates stress response.

  • Testosterone: involved in aggression, dominance, and mating behaviour.

In animals, these hormones can be manipulated experimentally, making it possible to establish cause-and-effect relationships between hormone levels and behavioural changes.

Pheromones in Animals

• Pheromones are airborne or secreted chemicals used by animals to communicate with others of the same species, especially in relation to mating, territory marking, or dominance.

• Animals detect pheromones via the olfactory system or the vomeronasal organ (VNO).

• Pheromonal communication is well-established in animals, unlike in humans where the evidence is more debated.

Animals - Genetics and Behaviour

In the biological approach to psychology, researchers investigate how specific genes influence behavioural traits and the development of mental disorders. These studies often look at:

• Gene expression and how it is influenced by the environment.

• Gene mutations or polymorphisms linked to traits like aggression, anxiety, or depression.

• Gene-environment interactions (GxE) — how genetic predispositions are shaped by life experiences.

Why Use Animal Models in Genetics Research?

Animal models (especially mice) are essential in genetic research because they allow:

• Direct genetic manipulation — such as removing or altering specific genes.

• Controlled breeding — enabling researchers to isolate the effects of genetic inheritance.

• Experimental control over the environment, making it easier to test gene-environment interactions.

• Many genetic structures are highly conserved between mice and humans, making findings biologically relevant.

Using genetically altered animals (e.g., knockout mice) allows researchers to observe how the absence or modification of a single gene can affect behaviour, something that cannot ethically or practically be done in humans.

Link to studies B+B - Animals

Rogers & Kesner (2003) – Role of Acetylcholine in Memory (Neurotransmitters)

• Application of K+U: This study used rats to investigate the role of the neurotransmitter acetylcholine in the formation of spatial memory.

• By injecting scopolamine (an acetylcholine antagonist) directly into the hippocampus, researchers could observe memory impairments during maze learning.

• The use of rats allowed precise manipulation of neurotransmitter function in a specific brain region—demonstrating localization of function and the importance of neurochemical processes in memory encoding.

🧪 Rosenzweig & Bennett (1972) – Environmental Effects on Brain Structure (Neuroplasticity)

• Application of K+U: This classic study examined how environmental stimulation affects brain development in rats.

• Rats placed in enriched environments developed thicker cerebral cortexes and more synaptic connections compared to those in deprived conditions.

• Animal models made it possible to control environmental exposure and then directly examine the structural effects on the brain, providing early and powerful evidence for experience-dependent neuroplasticity.

Link to studies H/P - Animals

Meaney et al. (1988)

Topic: Hormones — Cortisol (stress hormone)
Species: Rats
Focus: Investigated how maternal care (licking/grooming) affects the development of the hypothalamic-pituitary-adrenal (HPA) axis, which controls stress hormone release.

• Rats raised by low-licking/grooming mothers had higher baseline cortisol, poorer stress regulation, and impaired memory.

• This shows how early environmental factors in animals can permanently alter hormonal systems and behaviour — a process known as epigenetic modification.

🔗 K+U Link:
Animal models enabled researchers to track behavioural and physiological changes over time in a way that is not ethically possible in human infants. This study shows how hormonal regulation of stress can be shaped by early life experiences in animals.

Albert et al. (1986)

Topic: Hormones — Testosterone
Species: Rats
Focus: Investigated the role of testosterone in male aggression.

• Castration of male rats led to a significant reduction in aggressive behaviour toward intruders.

• When testosterone was reintroduced, aggression levels increased again.

🔗 K+U Link:
This study provides direct causal evidence that testosterone affects aggressive behaviour in animals. It also demonstrates the value of controlled hormone manipulation in animal models to study biological influences on social behaviour

Link to studies Genes - Animals

Cases et al. (1995)

Topic: MAOA gene mutation (animal model)
Species: Genetically modified knockout mice
Focus: Studied mice with a targeted deletion of the MAOA gene, which is involved in the breakdown of neurotransmitters like serotonin.

What They Found:

• MAOA knockout mice exhibited increased aggression, particularly during mating and territorial behaviours.

• Neurochemical analysis showed elevated serotonin levels in the brains of these mice — suggesting that the absence of the MAOA enzyme altered brain chemistry, leading to behavioural changes.

K+U Link:
This study shows how removing a single gene (MAOA) in animals can lead to specific, measurable changes in behaviour (aggression). It provides strong causal evidence for the link between genetics and behaviour. Animal models were essential because gene deletion is not ethically possible in humans, and the controlled environment reduced confounding variables.

Caspi et al. (2010)

Topic: 5-HTT gene polymorphism (human twin/family study)
Species: Humans
Focus: Investigated how variation in the 5-HTT gene (serotonin transporter) affects risk for depression, particularly when combined with life stress.

What They Found:

• Individuals with one or two copies of the short allele of the 5-HTT gene had a higher likelihood of developing depression in response to stressful life events.

• Suggests a gene-environment interaction (GxE) — the gene did not directly cause depression, but moderated the effect of environmental stress.

K+U Link:
Although this is a human study, it complements animal genetic research by showing that natural variation in genes influences behaviour, especially under environmental pressure. While it cannot establish causation (unlike animal knockout models), it shows the relevance of genes like 5-HTT in real-world psychological outcomes.