🧠 The Biological Approach to Understanding Behaviour: Study Notes 🧬
Hello future Psychologists! Welcome to the Biological Approach. Don't worry if this sounds intimidating—we are simply investigating one fundamental question: How does your physical body affect your mind and your actions?
This chapter is all about looking inside the machinery—your brain, your chemistry, and your DNA—to find explanations for why we think, feel, and behave the way we do. Mastering this section is crucial because it forms one-third of the Core knowledge required for Paper 1.
1. Core Principles of the Biological Approach
The biological approach operates under several fundamental assumptions:
- Behaviour is biological: All our actions, thoughts, and feelings originate from physiological factors (the body).
- Scientific study is possible: Since behaviour has a physical cause, it can be studied scientifically, usually involving laboratory experiments and advanced technology (like brain scans).
- Genetics and evolution play a role: Behaviour can be inherited, and many human behaviours are seen as adaptive mechanisms developed through natural selection.
1.1 Localization of Function
This principle suggests that specific parts of the brain are responsible for specific behaviours, emotions, or mental processes. Think of the brain as a highly efficient factory where different departments handle different jobs.
- Cortex: The outer layer, responsible for higher-level thinking, language, and memory.
- Hippocampus: Crucial for the formation of new long-term memories (like remembering what you had for dinner last night).
- Amygdala: Associated with emotions, particularly fear and threat detection (the brain’s "alarm system").
Did you know? The famous case of Phineas Gage provided early evidence for localization. After a metal rod destroyed his left frontal lobe, his personality changed drastically, supporting the idea that the frontal lobe controls complex planning and personality.
Quick Review: Localization suggests that if a specific area is damaged, only the function linked to that area should be impaired.
2. The Role of Chemical Messengers: Neurotransmitters, Hormones, and Pheromones
Your brain doesn't use Wi-Fi; it uses electrochemical signals! These chemicals are vital for communication throughout the body.
2.1 Neurotransmitters: The Fast, Local Messengers
Neurotransmitters are chemical substances released at the synapse (the tiny gap between neurons). They transmit signals from one neuron to another.
Step-by-Step Synaptic Transmission (The Neuron 'Text Message'):
- An Action Potential (electrical impulse) travels down the neuron.
- It reaches the terminal button and triggers the release of neurotransmitters into the synaptic gap.
- These chemicals cross the gap and bind to specific receptor sites on the receiving neuron (like a key fitting a lock).
- If enough binding occurs, the signal continues.
- The remaining neurotransmitters are broken down or sucked back up (reuptake).
Key Vocabulary:
- Agonist: A chemical (like a drug) that enhances the effect of a neurotransmitter (e.g., by blocking reuptake).
- Antagonist: A chemical that inhibits the effect of a neurotransmitter (e.g., by blocking the receptor site).
Example: Serotonin is often associated with mood, sleep, and appetite. Low levels are sometimes linked to depression. SSRIs (a type of antidepressant) are agonists that stop the reuptake of serotonin, allowing it to stay in the synapse longer and boost the signal.
2.2 Hormones: The Slower, Global Broadcasters
Unlike neurotransmitters which operate locally in the brain, hormones are chemicals secreted by endocrine glands (like the pituitary or adrenal glands) and travel through the bloodstream to target organs throughout the body.
Analogy: Neurotransmitters are like a quick phone call to the next room; Hormones are like a national radio broadcast—slower to start, but they reach every part of the system.
Key Hormone Example: Cortisol
Cortisol is a stress hormone released by the adrenal glands. While vital for short-term "fight or flight" responses, chronically high levels of cortisol can impair the immune system and damage the hippocampus, affecting memory.
2.3 Pheromones (HL Focus, but relevant for SL understanding of chemical messengers)
Pheromones are chemical signals released outside the body that affect the behaviour or physiology of another individual of the same species. In humans, the science is complex and debated, but research suggests they might influence reproductive cycles or mate selection.
Classic Study Connection: The McClintock (1971) study suggested that women living together sometimes experienced menstrual cycle synchronization, possibly due to pheromones released through sweat.
Key Takeaway: Chemistry is crucial! A slight change in chemical balance (whether fast-acting neurotransmitters or slow-acting hormones) can drastically alter mood, memory, and behaviour.
3. Genetics and Behaviour
Can shyness, intelligence, or even mental illness be inherited? Genetic research tries to answer this by determining the relative influence of nature (genes) versus nurture (environment).
3.1 Gene Expression
Every cell contains DNA, and segments of DNA are called genes. Genes are the blueprints. However, not all blueprints are active at once. Gene expression is the process where genetic information is turned into a functional product (like a protein) that influences traits or behaviour. The environment plays a huge role in determining whether a gene is "turned on" or "turned off."
Analogy: Your genes are the ingredients in your pantry. The environment (your chef skills, the recipe you follow) determines what kind of meal you make.
3.2 Genetic Research Methods
Since we cannot ethically manipulate human genes, psychologists use comparative studies to estimate the influence of genetic inheritance (heritability).
1. Twin Studies:
- Monozygotic (MZ) Twins: Identical, share 100% of their DNA.
- Dizygotic (DZ) Twins: Fraternal, share about 50% of their DNA (the same as regular siblings).
If MZ twins show a much higher concordance rate (the probability that if one twin has the trait, the other will too) than DZ twins, it suggests the trait is highly genetic.
2. Adoption Studies:
These compare adopted children to both their biological parents (nature) and their adoptive parents (nurture). If the child’s behaviour is more similar to their biological parents, the trait is considered more genetically determined.
3.3 The Environment is NOT Ignored
🛑 Common Mistake to Avoid: Assuming high heritability means the environment doesn't matter. This is wrong!
The **Diathesis-Stress Model** argues that individuals may have an inherited genetic predisposition (diathesis) for a disorder, but the disorder will only manifest if they encounter a severe environmental stressor.
Key Takeaway: Genes load the gun, but the environment pulls the trigger. Genetic research uses twin and adoption studies to measure heritability via concordance rates.
4. Evolutionary Explanations for Behaviour
The theory of evolution, primarily driven by Natural Selection (Charles Darwin), provides a long-term biological explanation for behaviour.
4.1 Natural Selection Basics
This process is based on three principles:
- Diversity: Within a species, there is natural variation in traits (e.g., some animals are faster, some have better camouflage).
- Fitness/Survival: Individuals with traits that give them a survival advantage (better suited to the environment) are more likely to survive and reproduce.
- Inheritance: These advantageous traits (and the genes coding for them) are passed on to the offspring.
Over generations, these adaptive traits become more common in the population. In psychology, we look at behaviour and mental processes as adaptive mechanisms.
Example: Fear Response. Why do humans universally fear snakes or spiders more easily than cars or electrical outlets? Because, historically, fearing small, venomous creatures (a fast, adaptive reaction) increased the chances of our ancestors surviving and passing on their genes. This is an evolutionarily beneficial behaviour.
Key Takeaway: Evolutionary psychology suggests that human behaviour today is the result of what helped our ancestors survive long ago.
5. Research Methods Used in the Biological Approach
The biological approach relies heavily on technology and scientific rigour to observe biological processes in action.
5.1 Brain Imaging Technology
These techniques allow researchers to see the structure and activity of the living brain.
- fMRI (Functional Magnetic Resonance Imaging): Measures brain activity by detecting changes in blood flow (oxygen usage). If a brain area is active, it uses more oxygenated blood.
Pro: Excellent spatial resolution (shows exactly where activity is). Con: Expensive, only shows correlation (activity doesn't prove causation). - EEG (Electroencephalography): Measures electrical brain activity using electrodes placed on the scalp.
Pro: Excellent temporal resolution (shows exactly *when* activity occurs). Con: Poor spatial resolution (hard to pinpoint the exact location).
5.2 Invasive Techniques (Often used with animals, but necessary for understanding)
Methods involving surgery or lesioning (destroying tissue) are used to study localization. While crucial for mapping brain function in animals, these are generally unethical for humans unless medically necessary (e.g., removing a tumor).
5.3 Ethical Considerations in Biological Research
Since this approach deals with sensitive physiological factors, ethics are paramount.
- Informed Consent: Especially necessary for studies involving risky procedures or genetics.
- Stigmatization/Labeling: Genetic research that links genes to specific disorders (e.g., aggression or mental illness) can lead to participants being stigmatized or discriminated against. Researchers must minimize this potential harm.
- Protection from Harm: Researchers using scans must ensure participants are comfortable, especially in noisy environments like fMRI machines.
Final Encouragement: You’ve tackled the complex link between mind and body! Remember to always connect the specific biological factor (like cortisol or a specific gene) back to the resulting human behaviour. Good luck!