Source: Chapters 1–4, General Psychology (Ohio State University)
Difficulty: Introductory | Prerequisites: None
Tags: psychology, scientific method, research methods, brain, neurons, neurotransmitters, nervous system, sensation, perception, consciousness, sleep, drugs, psychoactive substances, Wundt, IV DV, correlation, experiment
These four chapters form the foundation for everything else in the course. Chapter 1 introduces what psychology is, how psychologists think, and the methods they use to study behaviour. Chapters 2 and 3 move into the biological machinery behind behaviour (brain, neurons, senses) and how we interpret the world around us. Chapter 4 covers altered states of consciousness, from sleep cycles to psychoactive drugs. If you are joining the course late, start here: nearly every later topic assumes you are comfortable with these terms and methods.
Psychology is the scientific study of behaviour and mental processes. Researchers use experiments, correlational studies, and descriptive methods to test ideas. The brain and nervous system drive everything from reflexes to emotions, and the way we sense and perceive the world is shaped by both bottom-up input and top-down expectations. Consciousness exists on a spectrum, from focused awareness through sleep stages to drug-altered states.
Psychology
The scientific study of behaviour and mental processes. In simple terms, it is the discipline that asks "why do people do what they do?" and insists on evidence-based answers.
Critical thinking
Reflective thinking that involves evaluating evidence and arguments before accepting a claim. Think of it as the habit of asking "how do we know that?" rather than taking things at face value.
Wilhelm Wundt
Founded the first psychology laboratory; widely regarded as the "father of psychology." His lab marked the point where psychology became a separate science rather than a branch of philosophy.
Theory
A broad explanation for a set of observations (e.g., attachment theory). Think of it as the big-picture story that ties many findings together.
Hypothesis
A testable prediction derived from a theory (e.g., "Babies with secure attachment cry less when their caregiver returns"). In simple terms, it is the specific, falsifiable guess a researcher checks.
Independent variable (IV)
The variable the researcher manipulates in an experiment (e.g., caffeine dose).
Dependent variable (DV)
The variable the researcher measures as the outcome (e.g., alertness score).
Correlation coefficient
A number from -1.0 to +1.0 that describes the strength and direction of a relationship between two variables. A value near zero means little linear relationship; values near the extremes mean a strong one.
Random assignment
Assigning participants to experimental or control groups by chance, so that pre-existing differences are spread evenly across conditions.
Plasticity
The brain's ability to change and reorganise itself, especially after injury or new learning. Think of it as the brain's capacity to rewire.
Neuron
A nerve cell that sends and receives electrical and chemical signals. The basic information-processing unit of the nervous system.
Neurotransmitter
A chemical messenger released at the synapse that carries signals between neurons. Different neurotransmitters have different roles (dopamine for pleasure and movement, serotonin for mood and sleep, and so on).
Sympathetic nervous system
The branch of the autonomic nervous system that activates the body for emergencies ("fight or flight").
Parasympathetic nervous system
The branch that calms the body after the emergency has passed ("rest and digest").
Sensation
The process of detecting physical energy from the environment (light, sound, pressure). Think of it as raw data coming in.
Perception
The process of organising and interpreting sensory information so it becomes meaningful. Think of it as the brain making sense of the raw data.
Bottom-up processing
Perception driven by the sensory input itself, with no prior expectations guiding interpretation.
Top-down processing
Perception shaped by existing knowledge, expectations, or context.
Selective attention
Focusing on one stimulus while filtering out others. This is why you can read in a noisy room (most of the time).
Sensory adaptation
Decreased sensitivity to a constant, unchanging stimulus. You stop noticing a smell after a few minutes because your receptors dial down.
Consciousness
Awareness of yourself and your surroundings. Ranges from sharp, focused thought to the drifting of a daydream.
Circadian rhythm
A roughly 24-hour biological cycle that regulates sleep, wakefulness, body temperature, and hormone release.
REM sleep
A sleep stage characterised by rapid eye movement, vivid dreaming, and temporary muscle paralysis. Most dreaming occurs here.
Tolerance
Needing increasingly larger doses of a substance to achieve the same effect.
Psychoactive drug
Any chemical substance that alters mood, perception, or behaviour by acting on the nervous system.
Biological/Neuroscience – examines how brain structures, genetics, and neurochemistry shape behaviour.
Behavioural – focuses on observable behaviour and the environmental stimuli that reinforce or punish it.
Psychodynamic – emphasises unconscious conflicts and early-childhood experiences (rooted in Freud).
Humanistic – centres on personal growth, free will, and the drive toward self-actualisation.
Cognitive – studies internal mental processes such as memory, attention, and problem-solving.
Sociocultural – examines how culture, social norms, and group membership influence behaviour.
Biopsychosocial – integrates biological, psychological, and social factors into a single explanation. This is the approach most modern psychologists favour.
Descriptive research describes behaviour without explaining causes. Case studies, surveys, and naturalistic observation fall here.
Correlational research measures the relationship between two variables. A positive correlation means both rise together; a negative correlation means one rises as the other falls.
Correlation does not establish causation. Two variables can move together because of a third, unmeasured factor.
Experiments are the only method that can establish cause and effect, because the researcher manipulates an IV and measures the DV while controlling other variables.
The experimental group receives the treatment; the control group does not.
Random assignment helps ensure the groups are comparable before the manipulation begins.
The central nervous system (CNS) comprises the brain and spinal cord.
The peripheral nervous system connects the CNS to the rest of the body and divides into somatic (voluntary movement) and autonomic (involuntary functions) branches.
The fight-or-flight response is triggered by the sympathetic branch; the parasympathetic branch restores calm afterward.
Dendrites receive incoming signals.
Cell body (soma) maintains the neuron's life functions.
Axon carries signals away from the cell body toward the next neuron.
Myelin sheath insulates the axon and speeds up signal transmission.
Synapse is the tiny gap between neurons where neurotransmitters cross.
Dopamine – linked to pleasure, reward, and motor control. Excess is associated with schizophrenia; deficit with Parkinson's disease.
Serotonin – regulates mood, appetite, and sleep. Low levels are linked to depression.
Limbic system – involved in emotion and memory formation (includes the amygdala and hippocampus).
Amygdala – processes fear and threat detection.
Hippocampus – essential for forming new long-term memories.
Cerebral cortex – the outer layer responsible for higher-order thinking, language, and planning.
Four lobes of the cortex:
Frontal – planning, decision-making, personality.
Parietal – touch and spatial awareness.
Temporal – hearing and language comprehension.
Occipital – visual processing.
Motor cortex (frontal lobe) – controls voluntary movement.
Somatosensory cortex (parietal lobe) – processes touch information.
Corpus callosum – the fibre bundle connecting the left and right hemispheres.
Sensation is detection; perception is interpretation.
Perceptual constancy means we recognise objects as the same even when the sensory input changes (size constancy, shape constancy, colour constancy).
Gestalt principles (proximity, similarity, closure) describe how the brain groups sensory elements into coherent wholes.
Controlled processes require focused attention (solving a maths problem). Automatic processes run with little conscious effort (brushing teeth).
Non-REM sleep stages:
Stage 1 – light sleep, muscle twitches.
Stage 2 – sleep spindles, body temperature drops.
Stage 3 – deep/slow-wave sleep, hardest to wake from, important for physical restoration.
REM sleep – vivid dreams, memory consolidation, body temporarily paralysed.
Sleep disorders: insomnia (difficulty falling/staying asleep), narcolepsy (sudden sleep attacks), sleep apnea (repeated breathing interruptions).
Depressants slow neural activity (alcohol, benzodiazepines).
Stimulants increase neural activity (caffeine, nicotine, cocaine).
Hallucinogens distort perception (LSD, psilocybin).
Opioids relieve pain and carry high addiction risk (morphine, oxycodone).
Dependence can be physical (the body needs the substance) or psychological (emotional reliance).
Understanding the difference between correlation and causation helps you evaluate health headlines ("Coffee linked to longevity" does not mean coffee causes longer life).
Knowledge of neurotransmitters explains why SSRIs (which increase available serotonin) are prescribed for depression.
Sensory adaptation is the reason you stop smelling your own perfume but others still can.
Circadian-rhythm research underlies advice about consistent sleep schedules, screen-light reduction before bed, and the effects of shift work on health.
Students often confuse correlation with causation. A strong correlation (even r = .90) tells you nothing about which variable, if either, causes the other.
"Negative reinforcement" and "punishment" are frequently mixed up. Negative reinforcement removes something unpleasant to increase behaviour; punishment decreases behaviour. (Reinforcement concepts are covered fully in Chapter 5, but the confusion starts here.)
Many students assume the left brain is "creative" and the right brain is "logical." In reality both hemispheres contribute to most tasks; lateralisation is far more nuanced than the pop-culture version.
Students sometimes think REM is the "deepest" sleep. Stage 3 non-REM is the deepest; REM is characterised by brain activity that resembles wakefulness.
⚠️ Be able to identify the IV, DV, experimental group, and control group in a described experiment.
⚠️ Know the difference between correlation and causation, and be ready to explain why a correlation does not prove a causal link.
⚠️ The neuron pathway (dendrite → cell body → axon → synapse → next neuron) is a classic exam diagram or sequencing question.
⚠️ Distinguish the sympathetic and parasympathetic nervous systems by function and example.
⚠️ Know the four cortical lobes and one key function of each.
⚠️ Be able to list the sleep stages in order and identify which stage involves vivid dreaming.
⚠️ Know the three categories of psychoactive drugs (depressants, stimulants, hallucinogens) with at least one example of each.
True or False: A correlation of r = -0.85 is weaker than a correlation of r = +0.60.
The variable the researcher manipulates is the __________ variable.
True or False: The parasympathetic nervous system triggers the fight-or-flight response.
The brain structure most associated with forming new memories is the __________.
True or False: REM sleep is the deepest stage of sleep.
Answers: 1. False (strength is about the absolute value; 0.85 > 0.60). 2. Independent (IV). 3. False (that is the sympathetic system). 4. Hippocampus. 5. False (Stage 3 non-REM is deepest; REM features vivid dreams).
Q: A researcher finds that students who sleep more tend to have higher GPAs. Can she conclude that sleeping more causes higher grades? Why or why not?
A: No. This is a correlational finding. A third variable (e.g., better time-management skills) could explain both longer sleep and higher grades. Only an experiment with random assignment and a manipulated IV could establish causation.
Q: In an experiment testing whether background music improves reading comprehension, what is the IV and what is the DV?
A: The IV is the presence or type of background music (manipulated by the researcher). The DV is reading comprehension score (measured as the outcome).
Q: Name the four lobes of the cerebral cortex and one primary function of each.
A: Frontal (planning, decision-making), parietal (touch, spatial processing), temporal (hearing, language), occipital (vision).
Q: Explain the difference between sensation and perception with an example.
A: Sensation is detecting raw physical energy, such as light waves hitting the retina. Perception is the brain interpreting that input, for example recognising the pattern of light as a friend's face. Sensation is input; perception is meaning.
Q: A person needs three cups of coffee to feel the alertness that one cup used to provide. What concept does this illustrate?
A: Tolerance, the phenomenon in which repeated use of a substance leads to diminished effects, requiring larger doses.
The biopsychosocial approach introduced in Chapter 1 reappears throughout the course, especially in Chapters 12 (Psychological Disorders) and 14 (Health Psychology).
Neurotransmitter basics from Chapter 2 are essential background for understanding drug therapies in Chapter 13.
Top-down and bottom-up processing from Chapter 3 connect directly to cognitive biases and heuristics in Chapter 7.
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