Perception, cognition, emotion, personality, behaviour, interpersonal relationships, social groups, development across the lifespan. Both normal functioning and psychological disorders.
How it differs from common sense
Psychology uses empirical methods — experiments, surveys, brain imaging, longitudinal studies — to test intuitions that are often wrong. Many common beliefs (venting anger releases it, people use 10% of their brain, opposites attract) are contradicted by evidence.
Subfields
Clinical, cognitive, developmental, social, neuropsychology, forensic, educational, industrial/organisational, health psychology. Each uses different methods and addresses different questions.
Psychology vs psychiatry vs psychotherapy: Psychiatry is a medical speciality — psychiatrists are medical doctors (MDs) who can prescribe medication and make diagnoses. Psychology is a research and clinical discipline — clinical psychologists (usually PhD or PsyD) provide therapy and psychological assessment but in most countries cannot prescribe medication. Psychotherapy is the practice of using psychological methods to treat mental health problems — it can be practised by psychiatrists, psychologists, or trained psychotherapists/counsellors with various levels of qualification. See Part E for a full breakdown.
Part B · the founding figures — click to explore
Part C · the major schools of thought
Part D · therapy types — what each is for
Part E · who's who in mental health — the professional hierarchy
Psychiatrist (MD)
Medical doctor who specialised in psychiatry. Can diagnose mental disorders, prescribe medication (antidepressants, antipsychotics, mood stabilisers), and provide therapy. The highest level of medical authority in mental health.
Training: medical degree (5–6 years) + psychiatric residency (4–5 years). Can admit patients to hospital. Most appropriate for: severe mental illness (schizophrenia, bipolar disorder), medication management, complex cases.
Clinical psychologist (PhD/PsyD)
Doctoral-level specialist trained in psychological assessment, diagnosis, and therapy. Cannot prescribe medication in most countries (prescribing rights for psychologists exist in a few US states and some other jurisdictions). Strong emphasis on research and evidence-based practice.
Training: undergraduate + doctoral programme (4–7 years) + supervised clinical hours. Can diagnose using DSM/ICD. Most appropriate for: depression, anxiety, PTSD, eating disorders, personality disorders, neuropsychological assessment.
Psychotherapist / counsellor
Practises psychotherapy — using psychological methods to help people with emotional and mental health problems. Training and regulation varies widely by country and approach. "Psychotherapist" is not a legally protected title in all jurisdictions (unlike "psychologist" or "psychiatrist").
Training: varies from 2-year diploma to master's degree. Counsellors typically focus on specific issues (grief, relationships) with less intensive training. Most appropriate for: relationship issues, life transitions, mild-moderate depression and anxiety, bereavement.
Neuropsychologist
Specialist in the relationship between brain function and behaviour. Assesses cognitive deficits from brain injury, stroke, dementia, or developmental conditions. Doctoral level.
Most appropriate for: dementia assessment, post-stroke evaluation, traumatic brain injury, ADHD and learning disorder assessment, pre-surgical neurological evaluation.
Part F · essential psychological concepts everyone should know
Part G · test yourself
1. What is the difference between Freud's ego, id, and superego — and why is the model influential despite being scientifically unfalsifiable?
Freud's structural model divides the mind into three agencies. The id is entirely unconscious — the primitive, instinctual drives (sex and aggression primarily). It operates on the pleasure principle: immediate gratification with no regard for reality or consequences. The ego is partly conscious, partly unconscious — it mediates between the id's demands, the superego's constraints, and external reality. It operates on the reality principle, postponing gratification and navigating the real world. The superego is the internalised moral authority — parental rules, social norms, the conscience. It punishes via guilt and shame. Neurosis, in Freudian theory, results from the ego failing to manage the tensions between id and superego. The model is influential because it introduced ideas that became culturally pervasive and clinically useful as metaphors: the unconscious, repression, inner conflict, the role of childhood in adult psychology. It's scientifically problematic because it's unfalsifiable — any evidence against it can be "explained" by the theory (e.g., denying you're angry proves repression). Karl Popper used Freudian theory as his primary example of pseudoscience. Despite this, the framework generated enormous clinical practice and cultural understanding, and some core ideas (unconscious processing, the role of early relationships) have been validated by modern neuroscience even if the specific Freudian structure hasn't.
2. What is CBT and what is the core insight that makes it effective?
Cognitive Behavioural Therapy (CBT) is based on the insight that it is not events themselves that cause emotional distress, but the meaning we assign to them — our thoughts and interpretations. The core model: Situation → Thought → Emotion → Behaviour. The same situation (receiving criticism) will produce different emotions depending on the thought ("I'm worthless" vs "this is useful feedback"). CBT teaches patients to identify automatic negative thoughts, examine the evidence for and against them, and replace distorted thinking patterns with more accurate and helpful interpretations. The "behavioural" component addresses avoidance behaviours — the tendency to avoid feared situations, which provides short-term relief but long-term maintains the fear. CBT is the most extensively researched form of psychotherapy. It has strong evidence for depression, anxiety disorders, OCD, PTSD, eating disorders, and insomnia. It typically runs for 12–20 sessions and is explicitly goal-oriented and structured — unlike psychoanalytic therapies, which can run for years. It is skills-based: the goal is for patients to become their own therapist.
3. What is Maslow's hierarchy of needs, and what is the most important criticism of it?
Maslow's 1943 hierarchy proposes that human needs form a pyramid: Physiological (food, water, sleep) at the base, then Safety (security, stability), then Love/belonging (relationships, community), then Esteem (respect, achievement), then Self-actualisation (realising one's potential) at the apex. The idea: lower needs must be met before higher needs become motivating. The framework is intuitive, widely used in education, management, and therapy, and has cultural resonance. The main criticism: it is largely empirically unsupported. Cross-cultural research shows that people regularly pursue higher-order needs (connection, meaning, creativity) even when basic needs are unmet — prisoners have spiritual experiences, starving people create art, people in poverty report strong community bonds and meaning. The strict hierarchical sequencing is too rigid. Moreover, "self-actualisation" is vague and culture-specific. Maslow studied primarily healthy, successful people in constructing the theory, and later admitted his criteria for self-actualisation were based on a small, biased sample. The hierarchy is better understood as a useful heuristic than an empirically validated model.
4. What does "cognitive distortion" mean, and what are the most common ones to recognise in your own thinking?
Cognitive distortions (identified by Aaron Beck and later expanded by David Burns) are systematic errors in thinking — patterns of thought that are consistently inaccurate and negatively biased, maintaining depression and anxiety. The most important ones: All-or-nothing thinking (black-and-white, no middle ground: "I failed this one test — I'm a complete failure"). Catastrophising (assuming the worst outcome: "I'll probably lose my job and never recover"). Mind reading (assuming you know what others think without evidence: "They didn't reply — they must be angry with me"). Personalisation (taking blame for things outside your control: "My friend is in a bad mood — I must have caused it"). Should statements (rigid rules about how you or others must behave: "I should never feel anxious"). Emotional reasoning (treating feelings as facts: "I feel guilty so I must have done something wrong"). Overgeneralisation (one event becomes a universal rule: "This always happens to me"). Mental filter (dwelling on one negative detail while ignoring positives). The key insight: the mere presence of a thought or feeling doesn't mean it accurately reflects reality. Learning to notice these patterns and question them is the core skill of CBT.
5. What is the difference between classical and operant conditioning, and can you identify an example of each in everyday life?
Classical conditioning (Pavlov, Watson): learning through association. A neutral stimulus (bell) is paired with an unconditioned stimulus (food) that naturally produces a response (salivation). After repeated pairings, the neutral stimulus alone produces the response. The organism is passive — it doesn't "do" anything, it just learns an association. Everyday example: hearing a particular song that was playing during a breakup triggers sadness automatically. The song is the conditioned stimulus; the emotional state is the conditioned response. Also: anxiety when entering a dentist's waiting room (associated with past pain), or hunger triggered by the smell of a particular food associated with positive memories. Operant conditioning (Skinner): learning through consequences. Behaviour is strengthened by reinforcement (reward) or weakened by punishment. The organism is active — it learns that its behaviour has consequences. Positive reinforcement: adding something good (praise, pay) increases behaviour. Negative reinforcement: removing something bad (pain stops when you take paracetamol → you take paracetamol again) increases behaviour. Punishment decreases behaviour. Everyday examples: a slot machine (variable ratio reinforcement schedule — the most powerful for creating habitual behaviour) keeps people playing; checking social media for "likes" (variable ratio reinforcement of the checking behaviour); a child's tantrums increasing if parents give in (behaviour reinforced by getting what they want).