Welcome to Biological Psychology!
Welcome to one of the most exciting parts of your Psychology course! In this chapter, we are going to look "under the hood" of human behavior. Have you ever wondered why some people are more aggressive than others? Or how a tiny pill can change how someone feels?
Biological Psychology assumes that our thoughts, feelings, and behaviors all have a physical cause. We will explore the "wiring" of the brain, the chemicals that send messages, and how our evolutionary past still influences us today. Don't worry if the science seems a bit heavy at first—we’ll break it down piece by piece!
3.1 The Basics: How Your Brain Communicates
3.1.1 The Central Nervous System (CNS) and Neurotransmitters
The Central Nervous System (CNS) is made up of your brain and spinal cord. It is the "command center" of your body. To send messages, the CNS uses specialized cells called neurons.
The Structure of a Neuron
Think of a neuron like a tree:
• Dendrites: The "branches" that receive messages from other cells.
• Cell Body (Soma): The "trunk" that contains the nucleus.
• Axon: A long "cable" that carries an electrical impulse away from the cell body.
• Terminal Buttons: The "roots" at the end that pass the message to the next neuron.
Synaptic Transmission: The "Lock and Key" Analogy
Neurons don't actually touch! There is a tiny gap between them called a synapse. To cross this gap, the brain uses chemicals called neurotransmitters.
Step-by-Step Process:
1. An electrical impulse travels down the axon.
2. This triggers the release of neurotransmitters from tiny sacs (vesicles).
3. The chemicals float across the synaptic gap.
4. They bind to receptors on the next neuron. Think of the neurotransmitter as a key and the receptor as a lock—the message only sends if the key fits!
3.1.2 The Effect of Recreational Drugs
Recreational drugs (like cocaine or heroin) work by "hijacking" this transmission process. They can:
• Mimic natural neurotransmitters.
• Block receptors so messages can't get through.
• Overstimulate the reward system by flooding the synapse with Dopamine (the "feel-good" chemical).
Quick Review: The Basics
• CNS: Brain and Spinal Cord.
• Neuron: The messenger cell.
• Synapse: The gap between neurons.
• Neurotransmitter: The chemical "key."
3.2 Explaining Aggression
3.1.3 Brain Structure and Functioning
Why do some people "snap"? Psychologists look at specific brain areas:
• Pre-frontal Cortex (PFC): This is the "braking system" of the brain. It handles decision-making and impulse control. If the PFC is underactive, a person might act on aggressive urges without thinking.
• The Limbic System: This is the "emotional center." It includes areas that process fear and anger. If this area is overactive, a person might perceive threats where there are none.
3.1.6 The Role of Hormones (Testosterone)
Hormones are chemical messengers in the blood. Testosterone is often linked to aggression.
Analogy: If the brain is the engine, testosterone is the fuel that can make the engine run "hotter" and more aggressively.
3.1.4 Evolution and Natural Selection
According to Evolutionary Psychology, behaviors exist because they helped our ancestors survive. Aggression might have been useful for:
• Protecting offspring.
• Competing for food and resources.
• Defending territory.
3.1.5 An Alternative View: Freud’s Psychodynamic Explanation
Edexcel wants you to compare the biological view with Sigmund Freud's ideas. Freud believed personality has three parts:
• The Id: Our "inner brat"—it wants instant gratification and contains our aggressive drive (Thanatos).
• The Ego: The rational part that balances the Id and the world.
• The Superego: Our moral conscience (the "inner teacher").
Freud argued that aggression happens when we don't have a healthy way to release pressure. He suggested catharsis—the idea that playing sports or watching a violent movie can "vent" our aggression safely.
Key Takeaway
Aggression can be explained by Nature (low PFC activity, high testosterone, evolution) or Nurture/Psychological factors (Freud's Id and lack of catharsis).
3.3 Research Methods in Biological Psychology
3.2.1 Correlational Research
In a correlation, we look for a relationship between two co-variables (e.g., Is height related to aggression?).
Important: Correlations DO NOT show cause and effect. Just because two things happen together doesn't mean one caused the other!
Types of Correlation:
• Positive: As one variable goes up, the other goes up (e.g., more testosterone = more aggression).
• Negative: As one goes up, the other goes down (e.g., more sleep = less irritability).
• Zero: No relationship at all.
3.2.3 Brain Scanning Techniques
How do we see inside a living brain?
• CAT Scan: Uses X-rays to show the structure of the brain. Great for finding tumors or damage.
• PET Scan: Uses a radioactive tracer to show brain activity. It shows which parts are "burning" glucose.
• fMRI Scan: Shows both structure and activity by measuring blood oxygen levels. It's very detailed!
Twin and Adoption Studies
These are used to see if behavior is down to genetics (Nature) or environment (Nurture).
• Monozygotic (MZ) twins: 100% identical genes.
• Dizygotic (DZ) twins: 50% shared genes (like regular siblings).
If MZ twins are more similar in aggression than DZ twins, we assume it's mostly genetic!
3.4 Core Studies
Classic Study: Raine et al. (1997)
Aim: To see if murderers who pleaded Not Guilty by Reason of Insanity (NGRI) had different brain activity than non-murderers.
Method: Used PET scans on 41 murderers and 41 "normal" controls.
Results: The murderers had lower activity in the pre-frontal cortex (the part that controls impulses) and asymmetrical activity in the limbic system (the emotional part).
Conclusion: Brain abnormalities might make someone more likely to be violent, but it doesn't mean they are "born to kill"—environment still matters!
Contemporary Study: Brendgen et al. (2005)
Aim: To investigate whether social aggression (bullying/rumors) and physical aggression are caused by genes or environment.
Method: Studied 234 pairs of 6-year-old twins.
Results:
• Physical aggression was mostly genetic.
• Social aggression was mostly environmental (learned from parents or friends).
Key Finding: Children who are physically aggressive are more likely to become socially aggressive, but this is often due to their environment.
3.5 Mathematical Skills & Statistics
In this section, you need to know how to handle data. For correlations, we use Spearman’s Rho.
Spearman's Rank Correlation Coefficient Formula
\( r_s = 1 - \frac{6 \sum d^2}{n(n^2 - 1)} \)
Don't panic! You just need to know:
• \( d \): The difference between ranks.
• \( n \): The number of participants.
• If your observed value is higher than the critical value in the table (see Appendix 4), your result is significant!
Common Mistakes to Avoid
• Mixing up Neurons and Neurotransmitters: The neuron is the cell; the neurotransmitter is the chemical it sends.
• Saying Correlation = Causation: Never use the word "causes" when talking about a correlation. Use "link" or "relationship."
• Forgetting Freud: Students often focus only on the biology. Remember, Freud is a required "alternative" explanation for aggression in this syllabus!
Quick Review: Key Terms
Pre-frontal Cortex: The brain's "brakes" for behavior.
Testosterone: Male sex hormone linked to aggression.
MZ Twins: Identical twins used to study genetics.
Catharsis: Releasing aggressive energy through safe activities (Freud).
Significance: A statistical term meaning a result is unlikely to have happened by chance.
Keep going! Biological psychology can be tricky, but once you understand how the brain and chemicals work together, you'll see the world in a whole new way!