AP Psychology Unit 1 Notes: Scientific Foundations, Research Design, and Data Reasoning

Psychology

The scientific study of behavior (what organisms do) and mental processes (how organisms think, feel, perceive, and remember), using systematic observation and measurement.

Wilhelm Wundt

Founder of the first psychology laboratory (Leipzig, 1879); helped establish psychology as a field that studies the mind systematically.

Introspection

Early method in which trained participants reported their conscious experiences; important historically but limited because reports are subjective and hard to verify.

Behaviorism

Perspective arguing psychology should focus on observable behavior and how the environment shapes learning, emphasizing measurable variables and strong experimental design.

Cognitive approach

Approach that studies mental processes such as attention, memory, language, and problem-solving.

Biological approach

Approach explaining behavior and mental processes in terms of the brain, nervous system, hormones, and genetics.

Biopsychosocial approach

Framework viewing behavior as the product of interacting biological, psychological, and social-cultural influences.

Theory

A broad explanation that organizes observations and predicts outcomes.

Hypothesis

A testable prediction derived from a theory.

Operational definition

A clear, measurable definition of a variable (specifying exactly how it will be measured or manipulated).

Case study

An in-depth analysis of one individual (or a small group), useful for rare phenomena but limited in generalizability.

Naturalistic observation

Observing behavior in real-world settings without interference; provides realistic behavior but can be affected by bias/reactivity.

Hawthorne effect (reactivity)

A change in behavior that occurs because people know they are being observed.

Random sample

A sampling method in which every member of the population has an equal chance of being selected, supporting generalization to the population.

Random assignment

Placing participants into experimental conditions by chance to reduce preexisting differences between groups (supports causal inference).

Correlation

A measure of how strongly two variables vary together; useful for prediction but cannot establish cause-and-effect.

Experiment

A method that manipulates an independent variable (IV) and measures its effect on a dependent variable (DV) while controlling other factors; best for establishing causation.

Independent variable (IV)

In an experiment, the factor the researcher manipulates (e.g., caffeine vs. placebo).

Dependent variable (DV)

In an experiment, the outcome the researcher measures (e.g., reaction time).

Confounding variable

A factor that varies with the IV and could also affect the DV, threatening internal validity (the ability to conclude the IV caused the DV change).

Double-blind study

A study in which neither participants nor the researchers interacting with them know who is in which condition, reducing experimenter and participant expectation effects.

Standard deviation

A measure of variability indicating the typical distance of scores from the mean; larger values mean more spread-out scores.

Reliability

The consistency of a measure; a reliable test produces similar results under consistent conditions.

Validity

The extent to which a measure tests what it claims to measure (a test can be reliable without being valid).

Informed consent

Ethical requirement that participants understand the study’s purpose, procedures, risks, and their right to refuse or withdraw (within practical limits).