IB PSYCH BIOLOGICAL

Ethics of biological research

📌 Core idea
Biological research must follow ethical guidelines to protect participants (humans and animals) while still allowing scientific progress.

⚙ Key ethical principles (humans)

• Informed consent

  • Participants must understand the study and agree voluntarily

• Protection from harm

  • No physical or psychological harm beyond normal daily life

• Confidentiality

  • Personal data must be kept private

• Right to withdraw

  • Participants can leave at any time

• Deception (if used)

  • Must be justified and followed by full debriefing

• Debriefing

  • Participants are informed of the true purpose after the study

🐭 Animal research ethics

• Justification

  • Must have clear scientific value

• Minimize suffering

  • Reduce pain, stress, and discomfort

• 3Rs principle

  • Replace animals with alternatives when possible

  • Reduce number of animals used

  • Refine procedures to minimize harm

🧬 Why ethics matter in biological research

• Studies often involve brain manipulation, drugs, or invasive methods

• High risk of harm or long-term effects

• Must balance scientific benefit vs ethical cost

⚖ Evaluation
✔ Protects participants and maintains trust in science
✔ Ensures responsible and humane research practices
✔ Standardized guidelines improve study quality
❌ Can limit certain types of research (e.g., invasive brain studies)
❌ Ethical rules vary across countries/cultures
❌ Some important findings may be difficult to test ethically

Newcomer et al 1999

📌 Aim
To investigate how stress hormones (cortisol) affect memory performance

🔬 Method

• Experimental study with healthy participants

• Given different doses of cortisol (high, low, or placebo) over several days

• Tested on verbal declarative memory tasks (recalling words/stories)

📊 Findings

• Participants with high cortisol levels performed worse on memory tasks

• Lower doses had less impact

• Memory impairment was temporary (reversed after cortisol stopped)

🧠 Conclusion
High levels of cortisol (stress) can impair memory, especially long-term declarative memory

⚙ Biological explanation

• Cortisol affects the hippocampus, a brain area critical for memory

• Excess stress disrupts normal memory functioning

⚖ Evaluation
✔ Controlled experiment → strong cause-and-effect evidence
✔ Clear link between hormones and cognition
✔ Important real-world implications (stress, exams, trauma)
❌ Ethical concerns (hormone manipulation)
❌ Short-term study (limited long-term insight)
❌ Artificial setting may not reflect real-life stress fully

Milner 1966

🧠 Brenda Milner (1966) – HM Case Study

• Aim: Investigate the role of the hippocampus in memory

• Method: Case study of patient HM (after removal of hippocampus)

• Findings:

  • Could not form new long-term memories(anterograde amnesia)

  • Short-term memory intact

  • Learned new skills (e.g., mirror drawing) without remembering learning them

• Conclusion:

  • Hippocampus is critical for forming LTM

  • Supports Multi-Store Model (STM ≠ LTM)

  • Shows difference between declarative vs procedural memory

• ✔ High validity (real brain damage)

• ✔ Detailed data (case study)

• ❌ Not generalizable (one person)

• ❌ Lacks control

Research Methods in Biological Research

📌 Core idea
Biological research uses scientific methods to study the brain, hormones, genetics, and behavior, often combining lab techniques with real-world data.

🔬 Key research methods

• Laboratory experiments

  • Controlled environment to test cause-and-effect

  • Example: manipulating hormones (e.g., cortisol studies)

• Correlational studies

  • Examine relationships between variables (no causation)

  • Example: brain size vs intelligence

• Case studies

  • In-depth study of one individual

  • Example: brain-damaged patients (e.g., HM)

• Natural experiments

  • Study naturally occurring variables (no manipulation)

  • Useful when experiments would be unethical

🧠 Brain imaging techniques

• fMRI (functional magnetic resonance imaging)

  • Measures brain activity via blood flow

  • Shows which areas are active during tasks

• MRI (magnetic resonance imaging)

  • Produces detailed images of brain structure

• PET scans (positron emission tomography)

  • Uses radioactive tracers to show brain activity

🧬 Other biological methods

• Animal studies

  • Used to study brain function and genetics

  • Allow more control but raise ethical issues

• Post-mortem studies

  • Examine brains after death

  • Provide detailed structural insights

⚙ Strengths
✔ High control → allows cause-and-effect conclusions (experiments)
✔ Objective, scientific measurements (brain scans, hormones)
✔ Can link biology directly to behavior

⚖ Limitations
❌ Ethical constraints (invasive procedures, harm)
❌ Reductionist (may oversimplify behavior to biology alone)
❌ Some methods lack ecological validity (lab settings)
❌ Correlational methods cannot determine causation

Techniques used to study the brain

📌 Core idea
Scientists use different techniques to study brain structure and function, helping link biological processes to behavior.

🔬 Brain imaging techniques

• fMRI (functional Magnetic Resonance Imaging)

  • Measures brain activity via blood flow (oxygen levels)

  • Shows which areas are active during tasks

  • High spatial resolution

• MRI (Magnetic Resonance Imaging)

  • Produces detailed images of brain structure

  • Used to detect abnormalities (tumors, damage)

• PET scan (Positron Emission Tomography)

  • Uses radioactive tracers to measure brain activity

  • Shows how different brain regions function

⚙ Other key techniques

• EEG (Electroencephalogram)

  • Records electrical activity in the brain

  • Good for measuring brain waves and timing (high temporal resolution)

• Post-mortem studies

  • Examining the brain after death

  • Helps link structure to behavior (e.g., brain damage cases)

• Animal research

  • Allows controlled experiments on brain function

  • Used for studying neurochemistry and genetics

🧠 What they measure

• Structure → MRI, post-mortem

• Function → fMRI, PET

• Electrical activity → EEG

⚖ Evaluation
✔ Provide scientific, objective data about the brain
✔ Help link brain areas to behavior and cognition
✔ Non-invasive methods available (MRI, EEG)
❌ Some methods are expensive and complex
❌ PET involves radiation (ethical concerns)
❌ Brain activity ≠ exact thoughts (interpretation limits)

Maguire et al

📌 Aim
To investigate whether spatial navigation experience is associated with changes in brain structure

🔬 Method

• Quasi-experiment using MRI brain scans

• Participants:

  • London taxi drivers (experienced in navigation)

  • Control group (non-taxi drivers)

• Compared hippocampus size between groups

📊 Findings

• Taxi drivers had a larger posterior hippocampus

• Positive correlation between years of experience and hippocampus size

• Anterior hippocampus was slightly smaller

🧠 Conclusion
The brain is plastic (neuroplasticity) → it can change structure based on experience
→ Spatial navigation strengthens the hippocampus

⚙ Key concept

• Neuroplasticity: the brain adapts physically in response to learning and experience

⚖ Evaluation
✔ Real-world relevance (taxi drivers)
✔ Objective measurement (MRI scans)
✔ Strong evidence for brain plasticity
❌ Correlational → cannot prove cause-and-effect
❌ Pre-existing differences may exist
❌ Sample limited to specific group (taxi drivers)

Sharot et al

📌 Aim
To investigate how emotion affects memory accuracy and brain activity, especially for highly emotional events

🔬 Method

• Studied people who experienced the 2001 9/11 attacks

• Participants recalled their memories of the event

• Used brain imaging (fMRI) to observe brain activity during recall

• Compared emotional vs non-emotional memory processing

📊 Findings

• Emotional memories were more vivid and confidently recalled

• The amygdala showed higher activation during emotional recall

• However, some details were inaccurate or distorted despite high confidence

🧠 Conclusion
Emotion increases memory vividness and confidence, but does not guarantee accuracy
→ Emotional memories feel stronger but can still be reconstructive

⚖ Evaluation
✔ Strong biological + cognitive evidence (brain imaging + real event)
✔ High ecological validity (real-world traumatic event)
✔ Shows link between emotion and memory systems (amygdala involvement)
❌ Retrospective study → no control over original encoding
❌ Ethical concerns (trauma-related memories)
❌ Cannot fully determine cause-effect for accuracy vs emotion

Localization

📌 Core idea
Different parts of the brain are specialized for specific functions, meaning behavior can be linked to particular brain regions

🧠 Key brain areas + roles

• Frontal lobe → decision-making, personality, voluntary movement

• Parietal lobe → touch and sensory processing

• Temporal lobe → memory, hearing, language

• Occipital lobe → vision

🗣 Language localization

• Broca’s area → speech production

• Wernicke’s area → language comprehension

🔬 Supporting studies
Paul Broca

• Brain damage → loss of speech production (Broca’s aphasia)

Carl Wernicke

• Brain damage → impaired understanding but fluent speech

Eleanor Maguire

• Taxi drivers → larger hippocampus → spatial memory localization

⚙ Key concept

• Functions are localized but interconnected

• Brain areas work together in networks

⚖ Evaluation
✔ Supported by brain imaging and case studies
✔ Helps explain effects of brain damage
✔ Important for medicine and neuroscience
❌ Oversimplifies brain (functions often overlap)
❌ Neuroplasticity shows functions can shift
❌ Not all behaviors are strictly localized

Neuroplasticity

📌 Core idea
The brain can change, adapt, and reorganize itself in response to experience, learning, or injury

⚙ How it works

• Synaptic connections strengthen or weaken based on use

• New neural pathways can form through learning

• Brain can reorganize after damage (functions shift to other areas)

🧠 Types of plasticity

• Structural plasticity → physical changes in brain structure

• Functional plasticity → brain functions move to new areas after damage

🔬 Supporting research
Eleanor Maguire (2000)

• London taxi drivers → larger hippocampus from navigation experience

📊 Key features

• Stronger with practice and repetition

• More significant during childhood, but continues throughout life

• Can be positive (learning) or negative (addiction, maladaptive habits)

⚖ Evaluation
✔ Strong evidence from brain imaging studies
✔ Useful for rehabilitation (stroke, injury recovery)
✔ Shows brain is flexible, not fixed
❌ Not unlimited (some functions are hard to recover)
❌ Changes can be slow and require repetition
❌ Individual differences in plasticity

Rosenzweig, Bennett and Diamont

📌 Aim
To investigate how environmental enrichment affects brain development

🔬 Method

• Laboratory experiment using rats

• Two conditions:

  • Enriched environment → toys, social interaction, stimulation

  • Impoverished environment → isolated, no stimulation

• After time, rats’ brains were examined

📊 Findings

• Rats in enriched environments had:

  • Thicker cerebral cortex

  • More synaptic connections

• Impoverished rats showed less brain development

🧠 Conclusion
The brain changes based on experience → strong evidence for neuroplasticity

⚙ Key concept

• Environmental stimulation can physically change brain structure

⚖ Evaluation
✔ Strong experimental control → cause-and-effect
✔ Clear biological evidence of plasticity
✔ Influential in neuroscience and education
❌ Animal study → limited generalizability to humans
❌ Ethical concerns (animal treatment)
❌ Human environments are more complex

Neurotransmission

📌 Core idea
Neurotransmission is the process by which neurons communicate with each other using chemical signals (neurotransmitters)

⚙ How it works (step-by-step)

1. Electrical impulse travels down the neuron (action potential)

2. Reaches the axon terminal

3. Neurotransmitters are released into the synapse (gap between neurons)

4. They bind to receptors on the next neuron

5. This either excites or inhibits the next neuron

6. Neurotransmitters are then reabsorbed (reuptake) or broken down

🧠 Key components

• Neuron → nerve cell

• Synapse → gap between neurons

• Neurotransmitters → chemical messengers

• Receptors → binding sites on receiving neuron

🔬 Common neurotransmitters

• Dopamine → reward, motivation

• Serotonin → mood, sleep

• Acetylcholine → muscle movement, memory

⚖ Evaluation
✔ Strong scientific evidence (lab + brain studies)
✔ Explains biological basis of behavior and mental processes
✔ Important for understanding drugs and treatments
❌ Reductionist (focuses only on biology)
❌ Complex interactions not fully understood
❌ Hard to measure directly in real time in humans

Antonova

📌 Aim
To investigate how stress (cortisol) affects spatial memory and hippocampal activity

🔬 Method

• Laboratory experiment using fMRI brain scanning

• Participants: healthy adults

• Task: virtual reality navigation (spatial memory task)

• Two conditions:

  • Stress condition (induced cortisol release)

  • Control condition (no stress)

📊 Findings

• Stressed participants showed reduced hippocampal activity

• Worse performance on spatial memory tasks

• Non-stressed group performed better and showed normal hippocampal activation

🧠 Conclusion
Stress (via cortisol) can impair hippocampal function, leading to poorer spatial memory

⚙ Key biological explanation

• Cortisol affects the hippocampus, which is responsible for memory and spatial navigation

⚖ Evaluation
✔ Strong experimental + brain imaging evidence
✔ High ecological validity (realistic navigation task)
✔ Supports link between stress and cognition
❌ Artificial lab stress induction may not fully reflect real-life stress
❌ Small sample sizes typical of fMRI studies
❌ Cannot measure long-term stress effects

Rogers and Kesner

📌 Aim
To investigate the role of the neurotransmitter acetylcholine in memory formation (learning spatial information)

🔬 Method

• Laboratory experiment using rats

• Rats trained to run a maze task

• Some rats received drugs that blocked acetylcholine receptors

• Compared performance with control group

📊 Findings

• Rats with blocked acetylcholine:

  • Performed worse in maze learning

  • Had difficulty forming new memories

• Control group learned maze more effectively

🧠 Conclusion
Acetylcholine plays a key role in learning and memory formation, especially in the hippocampus

⚙ Key biological idea

• Neurotransmitters like acetylcholine are essential for synaptic communication in memory systems

⚖ Evaluation
✔ Strong experimental control → cause-and-effect
✔ Clear biological explanation of memory processes
✔ Supports role of neurotransmitters in cognition
❌ Animal study → limited generalizability to humans
❌ Drug manipulation may not fully reflect natural brain function
❌ Ethical concerns with animal use

Hormones

📌 Core idea
Hormones are chemical messengers released by endocrine glands that travel through the bloodstream and influence behavior, mood, and cognition

⚙ How hormones work

• Released by endocrine system (glands like adrenal, pituitary)

• Travel in blood to target organs or brain

• Bind to receptors and change physiological or psychological functioning

🧬 Key hormones & effects

• Cortisol (stress hormone)

  • Increases alertness in short term

  • Long-term high levels → memory impairment, hippocampus damage

• Adrenaline (epinephrine)

  • Activates “fight or flight” response

  • Increases heart rate and energy

• Testosterone

  • Linked to aggression, dominance, and risk-taking

• Oxytocin

  • Linked to bonding, trust, and social attachment

🔬 Supporting research examples
John W. Newcomer (1999)

• High cortisol levels → reduced memory performance

Tali Sharot (emotion + memory context)

• Hormonal/emotional arousal (amygdala activation) → stronger but sometimes inaccurate memories

⚖ Evaluation
✔ Strong biological evidence linking hormones to behavior
✔ Real-world applications (stress, health, learning, aggression)
✔ Supported by experimental and brain imaging studies
❌ Hormonal effects are complex and influenced by environment
❌ Difficult to isolate one hormone’s effect on behavior
❌ Reductionist (doesn’t fully explain cognition alone)

Cahill and McGaugh

📌 Aim
To investigate how emotional arousal affects memory retention and the role of the amygdala

🔬 Method

• Laboratory experiment with participants

• Participants heard a story with two versions:

  • Neutral version

  • Emotionally arousing version (involving a child in an accident)

• Tested recall of story details later

📊 Findings

• Participants remembered emotional version better than neutral version

• High emotional arousal led to stronger long-term memory retention

• The amygdala was key in enhancing memory consolidation

🧠 Conclusion
Emotional arousal improves memory by activating the amygdala, which strengthens memory storage in the brain

⚙ Key biological mechanism

• Amygdala activation → enhances interaction with hippocampus → stronger memory consolidation

⚖ Evaluation
✔ Strong experimental evidence
✔ Clear biological explanation (amygdala role)
✔ High relevance to real-life emotional events
❌ Ethical concerns due to distressing material
❌ Artificial lab story (not fully natural emotional experience)
❌ Individual differences in emotional response not fully controlled

Pheromones

📌 Core idea
Pheromones are chemical signals released by an individual that affect the behavior or physiology of other members of the same species

⚙ How they work

• Released into the environment (often through sweat or body fluids)

• Detected by others through specialized receptors

• Influence social and reproductive behaviors

🧬 Key effects (proposed in humans and animals)

• Attraction and mate selection

• Synchronization of menstrual cycles (controversial in humans)

• Recognition of kin or social bonding

• Territorial or dominance signaling

🐭 Strong evidence in animals

• Well-established in mice, insects, and other mammals

• Used for mating, warning signals, and territory marking

🧑 Human evidence (less certain)

• Some studies suggest subtle influence on attraction and mood

• However, findings are inconsistent and debated

⚖ Evaluation
✔ Strong evidence in animal behavior
✔ Useful for understanding evolutionary communication systems
✔ May play a role in unconscious human social behavior
❌ Very limited and inconsistent evidence in humans
❌ Difficult to isolate pheromonal effects from other cues (smell, vision, behavior)
❌ Some claims (e.g., menstrual synchrony) are heavily disputed

Mcclintock

📌 Aim
To investigate whether pheromones influence menstrual cycle synchronization in women

🔬 Method

• Field study in a female college dormitory

• Collected data on menstrual cycle start dates over time

• Compared cycles of women who lived close together

📊 Findings

• Women living in close proximity showed increased synchronization of menstrual cycles over time

• Suggested that pheromones released through sweat may influence others

🧠 Conclusion
Pheromones may play a role in human biological communication, influencing reproductive cycles

⚙ Key biological idea

• Chemical signals from one person may affect hormonal activity in others

⚖ Evaluation
✔ Real-world setting (high ecological validity)
✔ Influential early evidence for human pheromones
✔ Supports biological communication beyond conscious awareness
❌ Methodological issues (natural study, low control)
❌ Later research has questioned or failed to replicate findings
❌ Other factors (shared environment, coincidence) not fully controlled

wedekind

📌 Aim
To investigate whether human pheromones (MHC genes) influence mate preference and attraction

🔬 Method

• Male participants wore the same T-shirt for 2 nights without deodorant

• Female participants (not on hormonal contraception) smelled the shirts

• Rated which smells were most attractive

📊 Findings

• Women preferred the smell of men with different MHC genes (immune system genes)

• Suggests attraction may be influenced by genetic compatibility

• Women on the pill showed different or reversed preferences

🧠 Conclusion
Human smell may play a role in mate selection, helping choose partners with genetically different immune systems

⚙ Key biological idea

• MHC (Major Histocompatibility Complex) genes influence immune system diversity

• Smell may act as a biological compatibility signal

⚖ Evaluation
✔ Controlled experimental design
✔ Supports role of biological factors in attraction
✔ Suggests evolutionary advantage (stronger immune offspring)
❌ Small sample size
❌ Artificial lab setting (smelling shirts is not real-life dating)
❌ Findings may not generalize across cultures or contexts

Genes and behavior

📌 Core idea
Genes influence behavior by affecting brain structure, neurotransmitters, and hormone systems, creating predispositions rather than fixed outcomes

🧬 How genes influence behavior

• Genes code for proteins that affect brain development

• Influence neurotransmitter levels (e.g., serotonin, dopamine)

• Affect hormone production and sensitivity

• Create vulnerabilities or predispositions to behaviors

🧠 Key concept: nature vs nurture interaction

• Genes = biological predisposition

• Environment = triggers or suppresses genetic expression

• Behavior = result of gene–environment interaction

🔬 Supporting research examples
Kenneth S. Kendler (twin studies)

• Found moderate genetic influence on depression, but strong environmental role

Robert Plomin

• Showed that many traits (intelligence, personality) have heritability components

🧬 Methods used to study genes and behavior

• Twin studies (identical vs fraternal twins)

• Adoption studies (biological vs adoptive parents)

• Molecular genetics (specific gene identification)

⚖ Evaluation
✔ Strong evidence from twin and adoption studies
✔ Explains individual differences in behavior
✔ Supported by modern genetic research
❌ Genes rarely determine behavior alone (environment matters)
❌ Reductionist if taken as purely biological
❌ Complex traits are influenced by many genes (polygenic)

Kendler et al

📌 Aim
To investigate the role of genetics and environment in depression

🔬 Method

• Twin study using Swedish twin registry

• Compared monozygotic (identical) and dizygotic (fraternal) twins

• Measured rates of major depressive disorder

• Also assessed shared vs non-shared environmental factors

📊 Findings

• Higher concordance for depression in identical twins than fraternal twins

• Estimated moderate genetic influence on depression

• Environmental factors (especially non-shared) also played a major role

• Gene–environment interaction was important

🧠 Conclusion
Depression is influenced by both genetic vulnerability and environmental experiences, not one single cause

⚙ Key biological idea

• Genetic factors can create predisposition, but environment determines expression

⚖ Evaluation
✔ Large, well-controlled twin sample
✔ Strong evidence for nature + nurture interaction
✔ High reliability from registry data
❌ Cannot fully separate genetic and environmental influences
❌ Self-report measures of depression may lack accuracy
❌ Limited to Swedish population (cultural generalizability issues)

🔥 One-line memory trigger
👉 “Depression = genetic risk + environmental influence (not just genes)”

caspi et al

📌 Aim
To investigate how a specific gene interacts with stressful life events to influence depression risk

🔬 Method

• Longitudinal study using a large birth cohort in New Zealand

• Participants classified by 5-HTT gene variation (serotonin transporter gene):

  • short allele

  • long allele

• Measured exposure to stressful life events (e.g., abuse, loss, trauma)

• Assessed levels of depression over time

📊 Findings

• Individuals with the short allele + high stress were more likely to develop depression

• Long allele carriers were more resilient to stress

• Gene alone did not determine depression → interaction was key

🧠 Conclusion
Depression is influenced by gene–environment interaction, not genes alone
→ Genetic vulnerability is expressed only under environmental stress

⚙ Key biological idea

• 5-HTT gene affects serotonin regulation, influencing mood stability

⚖ Evaluation
✔ Strong longitudinal design (high reliability over time)
✔ Large sample increases validity
✔ Clear demonstration of gene–environment interaction
❌ Self-report of stress and depression may reduce accuracy
❌ Cannot fully control all environmental variables
❌ Ethical issues in studying trauma exposure

evolutionary arguments of behavior

📌 Core idea
Behavior is influenced by evolution through natural selection, where traits that improve survival and reproduction are more likely to be passed on

🧬 Key principles

• Natural selection → advantageous behaviors increase survival/reproduction

• Adaptation → behaviors that solve survival problems are selected for

• Survival value → behaviors exist because they were useful in ancestral environments

• Reproductive success → behaviors that increase mating success are favored

🧠 Examples of evolutionary explanations

• Aggression

  • May increase protection of resources and mates

  • Historically improved survival in competition

• Fear responses

  • Fear of snakes, heights → evolved survival advantage

• Mate selection

  • Preference for healthy, fertile partners increases reproductive success

• Parental investment

  • Caregiving behaviors increase offspring survival

🔬 Supporting concept
Charles Darwin

• Proposed theory of natural selection, forming the basis of evolutionary psychology

⚖ Evaluation
✔ Explains universal human behaviors across cultures
✔ Supported by evolutionary theory and cross-species comparisons
✔ Helps explain instinctive behaviors (fear, attraction, aggression)
❌ Often speculative (hard to test directly)
❌ May rely on “just-so stories” (post-hoc explanations)
❌ Underestimates cultural and social influences

Buss

📌 Aim
To investigate sex differences in mate preferences from an evolutionary perspective

🔬 Method

• Large cross-cultural survey

• Participants from 37 cultures

• Asked to rank traits preferred in a long-term partner

• Compared male vs female preferences

📊 Findings

• Males preferred:

  • Physical attractiveness

  • Youth (linked to fertility cues)

• Females preferred:

  • Financial resources

  • Status and ambition

  • Long-term stability

• These patterns were found across most cultures

🧠 Conclusion
Mate preferences support evolutionary explanations of behavior

• Men seek fertility cues

• Women seek resource security for offspring survival

⚙ Key evolutionary idea

• Sexual selection explains differences in mating strategies between sexes

⚖ Evaluation
✔ Very large, cross-cultural sample → strong validity
✔ Supports evolutionary theory of behavior
✔ Replicable findings across cultures
❌ Based on self-report (may not reflect real behavior)
❌ Cultural differences may still influence responses
❌ Oversimplifies human attraction (ignores social/media factors)