Key Concepts in Psychology: Units 0-5 Overview

Hindsight bias

After an event, the tendency to view outcomes as having been predictable all along. On exams, recognize that "I‑knew‑it‑all‑along" judgments often distort our memory of prior uncertainty. (e.g., thinking you "knew" the 2016 election outcome once the result is obvious)

Hypothesis

A falsifiable prediction, stated in operational terms, about the relationship between two or more variables. Good hypotheses specify independent and dependent variables and imply directionality (e.g., "Increased sleep will improve exam scores.").

Operational definition

The precise method by which a variable is measured or manipulated. Ensures replicability and clarity (e.g., defining "stress" as "cortisol levels above X micrograms per deciliter" rather than a vague feeling).

Control group

Participants who do not receive the experimental treatment, providing a baseline for comparison to isolate the independent variable's effect (e.g., placebo group in drug trials).

Random sample

Sampling technique in which every member of the population has an equal chance of selection, minimizing sampling bias and enhancing external validity.

Random assignment

Placing participants into experimental or control conditions by chance, ensuring groups are equivalent at the start and supporting causal inferences.

Case study

In‑depth examination of a single individual, group, or event. Offers rich qualitative data (e.g., Phineas Gage's frontal‑lobe injury), though limited in generalizability.

Naturalistic observation

Unobtrusive recording of behavior in real‑world settings without any manipulation. Useful for generating hypotheses (e.g., Jane Goodall's chimpanzee studies) but vulnerable to observer bias.

Survey

Questionnaire or interview designed to gather self‑reported attitudes or behaviors. Offers breadth of data quickly but can suffer from sampling bias and social desirability effects.

Sampling bias

Flawed sampling process that produces an unrepresentative sample (e.g., polling only one demographic group), threatening external validity.

Social desirability bias

Tendency for respondents to answer questions in a manner that will be viewed favorably by others, inflating reports of "good" behavior and deflating "bad."

Illusory correlation

Perception of a relationship between two variables when none exists (e.g., believing full moons increase psychiatric admissions despite no empirical link).

Double‑blind procedure

Neither participants nor experimenters know who receives the treatment versus placebo, preventing both subject and experimenter expectancy effects.

Placebo effect

Improvement resulting from mere expectation of improvement rather than the experimental treatment itself; common in drug trials.

Dependent variable

The outcome measure in an experiment, hypothesized to change as a function of the independent variable (e.g., test scores).

Independent variable

The factor manipulated by the researcher to observe its effect on the dependent variable (e.g., dosage level).

Confounding variable

An extraneous factor that varies along with the independent variable, potentially providing an alternative explanation for results (e.g., differing sleep environments when testing memory).

Experimenter bias

When a researcher's expectations influence the outcome by subtle cues or data‑handling decisions; mitigated by blinding and standardized procedures.

Informed consent

Ethical requirement that participants be told the basic outline of the study and potential risks before agreeing to take part.

Debriefing

Post‑experiment explanation of the study's purpose, any deception used, and the participants' right to withdraw their data.

Mode

The most frequently occurring score in a distribution; useful for categorical data (e.g., most common survey response).

Median

The middle value when scores are ordered from lowest to highest; resistant to outliers.

Mean

Arithmetic average of a set of scores; sensitive to extreme values but useful for inferential statistics.

Correlation coefficient (r)

Statistical index ranging from -1.00 to +1.00 indicating the strength and direction of a linear relationship between two variables (e.g., r = +.80 is a strong positive correlation).

Neurotransmitters

Chemical messengers released at synapses, binding to receptor sites on the postsynaptic neuron to excite or inhibit neural firing (e.g., dopamine in reward pathways; GABA as primary inhibitory transmitter).

Central nervous system (CNS)

Composed of the brain and spinal cord; processes sensory input, generates thoughts, and issues motor commands.

Peripheral nervous system (PNS)

All nerves outside the CNS; relays sensory information to the CNS and carries motor commands to muscles and glands.

Somatic nervous system

Subdivision of the PNS controlling voluntary skeletal muscles and conveying sensory information to the CNS.

Autonomic nervous system

Subdivision of the PNS regulating involuntary bodily functions (heart rate, digestion), divided into sympathetic and parasympathetic branches.

Sympathetic nervous system

"Fight‑or‑flight" branch of the autonomic system that increases heart rate, dilates pupils, and inhibits digestion under stress.

Antagonist

Molecule that binds to a receptor and blocks or dampens the neurotransmitter's effect (e.g., naloxone blocking opioid receptors).

Endocrine system

Network of glands that secrete hormones into the bloodstream, influencing growth, metabolism, and mood (e.g., adrenal glands releasing cortisol during stress).

Plasticity

Brain's capacity to reorganize after damage or experience; includes synaptic pruning and neurogenesis (e.g., musicians having enlarged motor cortex regions for finger movement).

Split brain

Condition following severing of the corpus callosum (often to stop severe epilepsy), resulting in limited interhemispheric communication; studies reveal lateralized functions (e.g., left hemisphere for language).

Heritability

Statistical estimate (0-1.0) of the proportion of variation in a trait among individuals attributable to genetic differences (e.g., IQ heritability increases with age).

Epigenetics

Study of how environmental factors (diet, stress) can switch genes on or off without altering the DNA sequence, affecting gene expression (e.g., prenatal stress impacting offspring).

Circadian rhythm

Biological clock governing ~24‑hour cycles of physiological processes (sleep-wake, hormone release), influenced by light exposure to the suprachiasmatic nucleus.

REM sleep

Sleep stage marked by rapid eye movements, vivid dreaming, and brainwave patterns similar to wakefulness; crucial for memory consolidation.

Insomnia

Chronic difficulty falling or staying asleep, leading to daytime impairment; can be treated with sleep hygiene or CBT‑I.

Narcolepsy

Neurological disorder characterized by uncontrollable sleep attacks and sudden loss of muscle tone (cataplexy), often linked to hypocretin deficiency.

Sleep apnea

Repeated cessation of breathing during sleep, leading to daytime fatigue and cardiovascular risks; treated with CPAP.

Manifest content

According to Freud, the literal storyline of a dream as remembered by the dreamer.

Latent content

Freud's underlying, symbolic meaning of dream elements, reflecting unconscious drives and wishes.

Tolerance

Diminishing effect of a drug with repeated use, requiring larger doses to achieve the same effect, often leading to dependence.

Addiction

Compulsive craving of drugs or behaviors despite negative consequences, characterized by withdrawal symptoms when use stops.

Withdrawal

Physical and psychological distress following abrupt discontinuation of a psychoactive substance.

Stimulant

Drug that increases neural activity and speeds up body functions (e.g., caffeine, amphetamines).

Depressant

Drug that reduces neural activity and slows body functions (e.g., alcohol, benzodiazepines).

Psychoactive drugs

Chemicals that alter perceptions, mood, consciousness, and behavior by affecting neurotransmission.

Hallucinogens

Drugs that produce perceptual distortions and hallucinations (e.g., LSD, psilocybin).

Agonist

Molecule that increases a neurotransmitter's action, either by mimicking its structure or blocking reuptake (e.g., SSRIs).

Encoding

First step in memory: transforming sensory input into a form that can be stored. Can be visual (images), acoustic (sounds), or semantic (meanings).

Storage

Maintaining encoded information over time, from fleeting sensory registers to potentially permanent long‑term repositories.

Retrieval

Bringing stored information into conscious awareness, measured via recall, recognition, or relearning tasks.

Parallel processing

Brain's ability to process multiple streams of information simultaneously (e.g., color, motion, depth) rather than in sequence.

Sensory memory

Brief (≤1 sec) retention of sensory input: iconic (visual) and echoic (auditory) memory allow momentary holding of stimuli.

Short‑term memory

Active memory that holds a few items (7 ± 2 chunks) for about 20-30 seconds, unless rehearsed.

Long‑term memory

Relatively permanent storage with seemingly unlimited capacity; organized by meaning and associations.

Explicit memories

Conscious memories of facts and experiences; depend on the hippocampus for encoding and consolidation.

Implicit memories

Unconscious retention of learned skills and procedures (e.g., riding a bike); rely on cerebellum and basal ganglia.

Iconic memory

Momentary sensory memory for visual stimuli lasting less than 1 second.

Chunking

Organizing information into meaningful units (e.g., remembering a 10‑digit phone number as three chunks).

Mnemonics

Memory aids that use vivid imagery or organizational devices (e.g., method of loci) to improve recall.

Flashbulb memory

Exceptionally vivid "snapshot" of an emotionally charged event, though sometimes prone to reconstruction errors.

Recall

Retrieval of information without explicit cues (e.g., essay tests).

Recognition

Identifying previously learned items when presented (e.g., multiple‑choice tests).

Mood‑congruent memory

Tendency to recall experiences consistent with current mood (e.g., recalling sad events when depressed).

Serial position effect

Better recall for items at the beginning (primacy) and end (recency) of a list.

Anterograde amnesia

Inability to form new long‑term memories after brain injury while still recalling events prior to injury.

Retrograde amnesia

Loss of memories for events that occurred before a traumatic injury.

Repression

Psychoanalytic defense mechanism of burying anxiety‑arousing thoughts and feelings into the unconscious.

Misinformation effect

Incorporating misleading post‑event information into memories, distorting recall.

Cognition

Mental processes involved in acquiring, storing, retrieving, and using information.

Convergent thinking

Narrowing multiple choices down to determine the single best solution; tested on intelligence and aptitude tasks.

Divergent thinking

Generating creative ideas by exploring many possible solutions; measured by tests of creativity.

Bottom‑up processing

Analysis beginning with sensory receptors, building up to the brain's integration of stimulus features.

Top‑down processing

Perception guided by higher‑level mental processes (expectations, prior knowledge) that interpret sensory data.

Change blindness

Failure to notice large changes in one's visual field when attention is elsewhere.

Inattentional blindness

Failure to notice unexpected objects because attention is engaged on another task (e.g., "gorilla" experiment).

Cocktail party effect

Ability to focus auditory attention on a single stimulus while filtering out a range of other stimuli, yet still notice salient information (like your name).

Selective attention

Focusing conscious awareness on a particular stimulus while ignoring others, allowing us to tune out unimportant background noise.

Selective inattention

Ignoring stimuli that are present, even if they may be important, because attention is elsewhere.

Sensory adaptation

Diminished sensitivity to a constant stimulus over time, freeing attention for more changing stimuli.

Depth perception

Ability to judge distance and see objects in three dimensions, enabled by binocular and monocular cues.

Visual cliff

Laboratory apparatus to test infants' depth perception; most infants refuse to crawl over the "cliff" side, indicating innate depth sensitivity.

Retinal disparity

Binocular cue arising from the slight difference between images projected on each retina; greater disparity indicates closer objects.

Convergence

Binocular cue in which the eyes turn inward to focus on near objects; the degree of muscle tension signals distance.

Relative size

Monocular cue: when two objects are similar, the smaller image is perceived as farther away.

Interposition

Monocular cue: when one object blocks another, the blocked object is perceived as farther away.

Linear perspective

Monocular cue: parallel lines appear to converge in the distance, with greater convergence indicating greater distance.

Perceptual constancy

Perceiving objects as unchanging (size, shape, color) despite shifts in illumination, distance, and angle.

Perceptual set

Mental predisposition to perceive one thing and not another, influenced by expectations and context.

Schema

Mental frameworks that organize and interpret information, affecting perception (e.g., seeing an ambiguous figure as either old woman or young girl).

Gestalt psychology

Emphasizes our tendency to integrate pieces of information into meaningful wholes, summarized by principles like proximity and closure.

Proximity

Gestalt principle: we group nearby figures together.

Habituation

Decrease in response to a stimulus after repeated exposure, allowing organisms to tune out unimportant stimuli.

Associative learning

Learning that certain events occur together; includes classical and operant conditioning.

Classical conditioning

Learning to link two stimuli, producing a new learned response (Pavlov's dogs learned to salivate at a bell).

Operant conditioning

Learning to associate behavior with its consequences; behaviors followed by reinforcers increase, by punishers decrease.

Acquisition

Initial phase of classical conditioning when the neutral stimulus becomes a conditioned stimulus eliciting a conditioned response.