- All-or-none principle
- A neuron fires a full-strength action potential once its threshold is crossed, or it does not fire at all. Stimulus intensity is coded by firing frequency, not impulse size.
- Action potential
- The brief electrical impulse that travels down a neuron's axon when threshold is reached; involves a rapid reversal of charge (depolarization).
- Resting potential
- The stable negative charge inside a neuron at rest (about −70 mV), maintained by the distribution of ions across the membrane.
- Threshold
- The level of stimulation a neuron must reach to fire an action potential.
- Refractory period
- A brief recovery phase after firing during which a neuron cannot fire again.
- Synapse
- The tiny gap between two neurons across which neurotransmitters carry a signal.
- Neurotransmitter
- A chemical messenger released into the synapse to carry a signal from one neuron to the next.
- Reuptake
- The reabsorption of leftover neurotransmitter molecules by the sending neuron. SSRIs work by blocking serotonin reuptake.
- Dopamine
- A neurotransmitter for reward, pleasure, and voluntary movement. Excess is linked to schizophrenia; depletion to Parkinson's disease.
- Serotonin
- A neurotransmitter affecting mood, sleep, and appetite. Low levels are linked to depression.
- Acetylcholine (ACh)
- A neurotransmitter for muscle movement and memory; its loss is associated with Alzheimer's disease.
- GABA
- The brain's main inhibitory neurotransmitter; it calms neural activity. Too little is linked to anxiety and seizures.
- Glutamate
- The brain's main excitatory neurotransmitter, important for memory and learning.
- Endorphins
- Natural opioid neurotransmitters that reduce pain and produce pleasure.
- Myelin sheath
- The fatty layer wrapped around many axons that insulates them and speeds neural transmission.
- Central nervous system (CNS)
- The brain and spinal cord — the body's command center.
- Peripheral nervous system (PNS)
- All the nerves outside the brain and spinal cord; it splits into the somatic and autonomic systems.
- Somatic nervous system
- The division of the PNS that controls voluntary skeletal-muscle movement.
- Autonomic nervous system
- The division of the PNS that controls automatic functions; it splits into the sympathetic and parasympathetic divisions.
- Sympathetic nervous system
- Arouses the body for 'fight or flight' — raising heart rate, dilating pupils, and releasing energy.
- Parasympathetic nervous system
- Calms the body and conserves energy — 'rest and digest' — after a stressor passes.
- Endocrine system
- The body's slower chemical communication system, using glands to release hormones into the bloodstream.
- Hypothalamus
- A brain structure that regulates hunger, thirst, body temperature, and the endocrine system.
- Hippocampus
- A brain structure essential for forming new long-term (explicit) memories.
- Amygdala
- A brain structure that processes fear, aggression, and emotional memory.
- Cerebellum
- The 'little brain' at the rear that coordinates balance, movement, and procedural memory.
- Medulla
- A brainstem structure that controls automatic survival functions like heartbeat and breathing.
- Frontal lobe
- The cortical lobe responsible for judgment, planning, decision-making, and voluntary movement.
- Occipital lobe
- The cortical lobe at the back of the brain that processes vision.
- Temporal lobe
- The cortical lobe that processes hearing and language comprehension.
- Corpus callosum
- The thick band of fibers connecting the brain's left and right hemispheres.
- Neuroplasticity
- The brain's ability to reorganize itself by forming new neural connections, especially after learning or injury.
- Circadian rhythm
- The roughly 24-hour biological clock that governs the sleep-wake cycle.
- REM sleep
- Rapid eye movement sleep, when most vivid dreaming occurs; the body is largely paralyzed but the brain is active.
- Sensory adaptation
- Reduced sensitivity to a constant, unchanging stimulus over time.
- Agonist
- A drug that mimics or increases a neurotransmitter's action.
- Antagonist
- A drug that blocks or reduces a neurotransmitter's action.
- Pituitary gland
- The 'master gland' of the endocrine system; it releases hormones that control other glands.
- Adrenal glands
- Endocrine glands that release epinephrine and norepinephrine to trigger the body's stress response.
- Broca's vs Wernicke's area
- Broca's area (frontal lobe) controls speech production; Wernicke's area (temporal lobe) controls language comprehension.
- Sensation vs perception
- Sensation is detecting raw stimuli through the senses; perception is organizing and interpreting that information.
- Bottom-up processing
- Building perception from raw sensory features upward, assembling the whole from the parts.
- Top-down processing
- Using prior knowledge, context, and expectations to interpret sensory information.
- Absolute threshold
- The minimum stimulus intensity needed to detect a stimulus 50% of the time.
- Difference threshold (JND)
- The smallest detectable difference between two stimuli; also called the just-noticeable difference.
- Weber's law
- The principle that two stimuli must differ by a constant proportion (not a constant amount) to be perceived as different.
- Gestalt principles
- Rules describing how we group visual elements into wholes: figure-ground, proximity, similarity, closure, and continuity.
- Figure-ground
- The Gestalt tendency to organize a scene into a main object (figure) and its background (ground).
- Perceptual set
- A readiness to perceive something in a particular way, shaped by expectations and experience.
- Sensory memory
- A momentary, exact record of sensory information that lasts a fraction of a second before fading.
- Short-term / working memory
- The active store holding about 7±2 items for roughly 15–30 seconds; rehearsal and chunking extend it.
- Long-term memory
- The relatively permanent, large-capacity store of knowledge, skills, and experiences.
- Encoding
- The process of getting information into memory; deeper, more meaningful processing encodes more durably.
- Chunking
- Grouping items into meaningful units to expand short-term memory capacity (e.g., a phone number in segments).
- Serial position effect
- The tendency to recall the first (primacy) and last (recency) items in a list better than the middle.
- Primacy effect
- Better recall of items at the start of a list, because they were rehearsed into long-term memory.
- Recency effect
- Better recall of items at the end of a list, because they are still in short-term memory.
- Proactive interference
- When old information disrupts the recall of newly learned information.
- Retroactive interference
- When newly learned information disrupts the recall of older information.
- Misinformation effect
- When misleading information after an event distorts a person's memory of it (Loftus).
- Encoding specificity
- The principle that retrieval is easier when cues present at learning are also present at recall (context- and state-dependent memory).
- Explicit vs implicit memory
- Explicit (declarative) memory is consciously recalled facts and events; implicit memory includes skills and conditioned associations.
- Algorithm
- A step-by-step procedure that guarantees a solution, though it can be slow.
- Heuristic
- A fast mental shortcut for problem-solving that is efficient but can lead to errors.
- Availability heuristic
- Judging how likely an event is by how easily examples come to mind, making vivid events seem more common.
- Representativeness heuristic
- Judging likelihood by how well something matches a prototype, often ignoring base rates.
- Confirmation bias
- The tendency to seek and favor information that confirms one's existing beliefs.
- Framing effect
- How the wording or presentation of a choice influences the decision made.
- Hindsight bias
- The 'I knew it all along' tendency to see an outcome as predictable after it has occurred.
- Functional fixedness
- The tendency to see objects only in their usual use, which can block a solution.
- Mental set
- The tendency to approach a problem in a way that worked before, even when a better method exists.
- Convergent vs divergent thinking
- Convergent thinking narrows to one best answer; divergent thinking generates many possible solutions (creativity).
- Prototype
- A mental 'best example' of a category used to classify new items quickly.
- Phonological loop
- The component of working memory that holds and rehearses verbal and auditory information.
- Visuospatial sketchpad
- The component of working memory that holds and manipulates visual and spatial information.
- Spacing effect
- The finding that information is retained better when study is distributed over time rather than crammed.
- State-dependent memory
- Improved recall when one's physical or emotional state at retrieval matches the state at encoding.
- Recognition vs recall
- Recognition identifies previously learned material (multiple choice); recall retrieves it without cues (fill-in-the-blank).
- Selective attention
- Focusing conscious awareness on one stimulus while filtering out others (e.g., the cocktail-party effect).
- Working memory model
- Baddeley's model of short-term memory with a central executive directing the phonological loop and visuospatial sketchpad.
- Object permanence
- Knowing an object still exists even when out of sight; gained in Piaget's sensorimotor stage.
- Piaget's sensorimotor stage
- Birth to ~2 years: infants learn through senses and actions and gain object permanence.
- Piaget's preoperational stage
- ~2–7 years: symbolic thought develops but reasoning is egocentric and lacks conservation.
- Piaget's concrete operational stage
- ~7–11 years: logical thought about concrete events; the child masters conservation.
- Piaget's formal operational stage
- ~12+ years: abstract, hypothetical, and systematic reasoning becomes possible.
- Conservation
- The understanding that quantity stays the same despite changes in shape or appearance.
- Egocentrism
- The preoperational child's difficulty taking another person's point of view.
- Schema
- A mental framework that organizes and interprets information, built through experience.
- Assimilation
- Fitting new information into an existing schema (calling a cat a 'dog').
- Accommodation
- Changing an existing schema to fit new information (learning cats differ from dogs).
- Vygotsky's zone of proximal development
- The gap between what a learner can do alone and what they can do with guidance.
- Scaffolding
- Providing just enough support to help a learner accomplish a task, then gradually removing it.
- Erikson's psychosocial stages
- Eight lifespan stages, each a crisis (e.g., trust vs mistrust in infancy; identity vs role confusion in adolescence).
- Trust vs mistrust
- Erikson's first stage (infancy): the infant learns whether the world is reliable and safe.
- Identity vs role confusion
- Erikson's adolescent stage: forming a coherent sense of self.
- Kohlberg's stages of moral development
- Three levels of moral reasoning: preconventional (rewards/punishment), conventional (social rules), and postconventional (ethical principles).
- Attachment
- The enduring emotional bond between an infant and a caregiver.
- Ainsworth's Strange Situation
- An experiment classifying infant attachment as secure or insecure (avoidant/anxious) based on reactions to separation and reunion.
- Secure attachment
- An infant who explores freely with a caregiver present and is comforted on reunion after distress.
- Harlow's monkey experiments
- Showed infant monkeys preferred a soft cloth 'mother' for contact comfort over a wire one that fed them.
- Classical conditioning
- Learning by association: a neutral stimulus paired with one that triggers a reflex comes to trigger that response (Pavlov).
- Unconditioned stimulus (UCS)
- A stimulus that naturally triggers a response (food causing salivation).
- Conditioned stimulus (CS)
- A formerly neutral stimulus that, after pairing, triggers a learned response (a bell causing salivation).
- Conditioned response (CR)
- The learned response to a previously neutral, now conditioned, stimulus.
- Acquisition
- The initial stage of learning a conditioned response by pairing the CS and UCS.
- Extinction (conditioning)
- The weakening and disappearance of a conditioned response when the CS is repeatedly presented without the UCS.
- Spontaneous recovery
- The reappearance of an extinguished conditioned response after a pause.
- Generalization
- Responding to stimuli similar to the conditioned stimulus.
- Discrimination (conditioning)
- Learning to respond only to the specific conditioned stimulus and not to similar ones.
- Operant conditioning
- Learning in which voluntary behavior is strengthened by reinforcement or weakened by punishment (Skinner).
- Positive reinforcement
- Adding a pleasant stimulus after a behavior to make it more likely.
- Negative reinforcement
- Removing an unpleasant stimulus after a behavior to make it more likely — not punishment.
- Positive punishment
- Adding an unpleasant stimulus after a behavior to make it less likely.
- Negative punishment
- Removing a pleasant stimulus after a behavior to make it less likely.
- Variable-ratio schedule
- Reinforcement after an unpredictable number of responses (like a slot machine); it produces high, persistent response rates.
- Fixed-ratio schedule
- Reinforcement after a set number of responses (e.g., every 10th sale earns a bonus).
- Shaping
- Reinforcing successive approximations of a target behavior to gradually train it.
- Observational learning
- Learning by watching and imitating others; demonstrated in Bandura's Bobo doll study.
- Bandura's Bobo doll study
- Showed children imitate aggressive behavior they observe in adult models.
- Latent learning
- Learning that occurs without reinforcement and stays hidden until there is a reason to use it (Tolman).
- Fundamental attribution error
- Overestimating personality and underestimating the situation when explaining others' behavior.
- Self-serving bias
- Attributing one's successes to internal factors and failures to external ones.
- Cognitive dissonance
- The discomfort felt when actions clash with attitudes; people often change the attitude to match (Festinger).
- Conformity
- Adjusting behavior or thinking to match a group standard, shown in Asch's line studies.
- Asch conformity experiment
- Found people often gave an obviously wrong answer to match a unanimous group.
- Obedience (Milgram)
- Milgram's study showed people will obey an authority figure even to the point of harming another person.
- Foot-in-the-door technique
- Gaining compliance with a large request by first getting agreement to a small one.
- Groupthink
- When a group's desire for harmony overrides realistic appraisal of alternatives.
- Group polarization
- The tendency for group discussion to strengthen members' already-held attitudes.
- Bystander effect
- The more onlookers present, the less likely any one of them is to help (diffusion of responsibility).
- Social facilitation
- Performing a well-learned task better in the presence of others.
- Social loafing
- Exerting less effort on a task when working in a group than when alone.
- Just-world hypothesis
- The belief that the world is fair, so people get what they deserve.
- In-group bias
- Favoring one's own group over out-groups.
- Stereotype
- A generalized belief about a group of people.
- Big Five (OCEAN)
- The five trait dimensions of personality: Openness, Conscientiousness, Extraversion, Agreeableness, and Neuroticism.
- Trait theory
- The view that personality is made of stable characteristics (traits) that can be measured along continuums.
- Id, ego, superego
- Freud's structure of personality: the id seeks pleasure, the superego enforces morality, and the ego mediates with reality.
- Pleasure principle
- The id's drive to seek immediate gratification of needs and wants.
- Defense mechanisms
- Freud's unconscious strategies (repression, projection, displacement, denial) the ego uses to reduce anxiety.
- Projection (defense)
- Attributing one's own unacceptable thoughts or impulses to someone else.
- Displacement (defense)
- Redirecting an impulse from its real target onto a safer one.
- Humanistic theory
- The view that people are driven toward growth and self-actualization (Maslow, Rogers).
- Maslow's hierarchy of needs
- A pyramid of needs from physiological to safety, belongingness, esteem, and self-actualization at the top.
- Self-actualization
- The realization of one's full potential, at the top of Maslow's hierarchy.
- Unconditional positive regard
- Rogers's idea of accepting and valuing a person without conditions, central to client-centered therapy.
- Self-efficacy
- A person's belief in their ability to succeed at a specific task (Bandura).
- Reciprocal determinism
- Bandura's idea that behavior, thoughts, and environment continuously influence one another.
- Locus of control
- Whether a person believes outcomes depend on their own actions (internal) or on luck and fate (external).
- Drive-reduction theory
- The idea that a physiological need creates a drive that motivates behavior to reduce it and restore balance.
- Yerkes-Dodson law
- Performance peaks at a moderate level of arousal; too little or too much arousal lowers it.
- James-Lange theory
- The theory that emotion follows from awareness of a physiological response (we feel afraid because we tremble).
- Cannon-Bard theory
- The theory that a stimulus triggers a physiological response and an emotion simultaneously.
- Schachter-Singer two-factor theory
- The theory that emotion requires physiological arousal plus a cognitive label for that arousal.
- Intrinsic vs extrinsic motivation
- Intrinsic motivation comes from internal satisfaction; extrinsic motivation comes from external rewards or pressures.
- Central route persuasion
- Persuasion through careful consideration of the strength of an argument's evidence.
- Peripheral route persuasion
- Persuasion through superficial cues like attractiveness or emotion rather than the argument itself.
- Mere exposure effect
- The tendency to develop a preference for things simply because we are repeatedly exposed to them.
- Door-in-the-face technique
- Gaining compliance with a moderate request by first making a large request that is refused.
- Diffusion of responsibility
- The reduced sense of personal accountability when others are present, underlying the bystander effect.
- Diathesis-stress model
- Disorders arise when a predisposition (diathesis) interacts with environmental stress.
- Biopsychosocial model
- The view that biological, psychological, and social factors together shape health and disorder.
- Generalized anxiety disorder
- Persistent, free-floating worry and tension most days for six months or more.
- Panic disorder
- Recurrent, unexpected panic attacks with intense fear and physical symptoms.
- Specific phobia
- An intense, persistent, irrational fear of a particular object or situation.
- Major depressive disorder
- At least two weeks of deep sadness, loss of interest, and low energy that impair functioning.
- Bipolar disorder
- A mood disorder alternating between depressive episodes and manic, high-energy episodes.
- Obsessive-compulsive disorder (OCD)
- Intrusive, unwanted thoughts (obsessions) and repetitive behaviors (compulsions) performed to reduce anxiety.
- Post-traumatic stress disorder (PTSD)
- Flashbacks, nightmares, and hypervigilance lasting more than a month after a traumatic event.
- Schizophrenia
- A disorder marked by disturbed thinking, hallucinations, delusions, and disorganized speech or behavior.
- Positive symptoms (schizophrenia)
- Added experiences not normally present — hallucinations, delusions, and disorganized speech.
- Negative symptoms (schizophrenia)
- Reduced or absent normal functions — flat affect, social withdrawal, and reduced speech.
- Delusion
- A firmly held false belief that persists despite contrary evidence.
- Hallucination
- A sensory experience without an external stimulus, such as hearing voices that are not there.
- Dissociative identity disorder
- A disorder in which a person shows two or more distinct identities or personality states.
- Anorexia nervosa
- An eating disorder marked by self-starvation and a distorted body image despite being underweight.
- Bulimia nervosa
- An eating disorder marked by cycles of binge eating followed by compensatory purging.
- ADHD
- Attention-deficit/hyperactivity disorder: persistent inattention and/or hyperactivity-impulsivity that impairs functioning.
- Autism spectrum disorder
- A neurodevelopmental disorder marked by challenges in social communication and restricted, repetitive behaviors.
- DSM-5
- The Diagnostic and Statistical Manual of Mental Disorders, the standard classification system for diagnosing disorders.
- Cognitive behavioral therapy (CBT)
- A widely supported therapy that challenges distorted thoughts and changes maladaptive behavior.
- Systematic desensitization
- A behavioral therapy pairing relaxation with a gradual hierarchy of feared situations to reduce anxiety.
- Token economy
- A behavioral technique that reinforces desired behaviors with tokens exchangeable for rewards.
- Exposure therapy
- Treating anxiety by gradually exposing a person to the feared stimulus until the fear subsides.
- Psychoanalysis
- Freud's therapy aiming to surface unconscious conflicts through techniques like free association.
- Client-centered therapy
- Rogers's humanistic therapy using empathy, active listening, and unconditional positive regard.
- Biomedical therapy
- Treating disorders with medication or medical procedures such as antidepressants, antipsychotics, or ECT.
- Antidepressants (SSRIs)
- Medications that relieve depression by blocking the reuptake of serotonin, raising its availability.
- Antipsychotic drugs
- Medications that reduce psychotic symptoms, often by blocking dopamine activity.
- Free association
- A psychoanalytic technique in which a patient says whatever comes to mind to reveal unconscious material.
- General adaptation syndrome
- Selye's three-stage stress response: alarm, resistance, and exhaustion.
- Problem-focused coping
- Reducing stress by directly addressing and changing the stressor itself.
- Emotion-focused coping
- Reducing stress by managing one's emotional response rather than changing the stressor.
- Stressor
- Any event or condition that the body perceives as a threat or challenge, triggering the stress response.
- Positive psychology
- The scientific study of human strengths, well-being, and what helps people thrive.
- Tolerance (drugs)
- Needing increasing amounts of a substance to achieve the same effect over time.
- Withdrawal
- The unpleasant physical and psychological symptoms that follow stopping a dependent substance.
- Medical model
- The view that psychological disorders have physical causes that can be diagnosed and treated.
- Comorbidity
- The presence of two or more disorders in the same person at the same time.
- Resilience
- The ability to recover and adapt well in the face of adversity, trauma, or significant stress.