Scientific Foundations of Psychology: every key term you need (+ practice quiz)

More AP Psychology guides

• Biological Bases of Behavior
• Sensation and Perception
• Learning
• Cognitive Psychology
• Developmental Psychology

Wilhelm Wundt

Founded the first psychology laboratory in Leipzig, Germany, in 1879; marked psychology's start as a science.

Structuralism

Early school (Titchener) that used introspection to break consciousness into basic elements of sensation and feeling.

Functionalism

School (William James) that studied the purpose (function) of consciousness and how behaviors help organisms adapt.

Psychoanalytic Perspective

Freud's view that behavior stems from unconscious drives and childhood conflicts.

Behavioral Perspective

Focuses on observable behavior learned through conditioning (Watson, Skinner); rejects study of the mind.

Humanistic Perspective

Emphasizes free will, personal growth, and self-actualization (Maslow, Rogers).

Cognitive Perspective

Studies how people think, remember, and process information.

Biological Perspective

Explains behavior through genetics, brain structures, neurotransmitters, and physiology.

Evolutionary Perspective

Explains behavior and mental traits as adaptations shaped by natural selection.

Sociocultural Perspective

Examines how culture, social norms, and environment shape thought and behavior.

Hypothesis

A testable, falsifiable prediction about the relationship between variables.

Operational Definition

A precise statement of how a variable is measured or manipulated, allowing replication.

Independent Variable

The factor the experimenter manipulates to observe its effect on the dependent variable.

Dependent Variable

The outcome that is measured; it may change in response to the independent variable.

Random Assignment

Placing participants into groups by chance, equalizing traits and allowing cause-effect conclusions.

Confounding Variable

An uncontrolled factor other than the IV that could explain changes in the DV.

Experimental vs Control Group

Experimental group receives the treatment; control group does not, serving as the comparison baseline.

Placebo Effect

Improvement caused by expectations rather than the treatment itself; addressed with a placebo control.

Double-Blind Procedure

Neither participants nor researchers know group assignments, reducing bias and demand characteristics.

Correlation vs Causation

Correlation shows two variables relate, but only a controlled experiment can establish cause and effect.

Correlation Coefficient

A number from -1 to +1 showing the strength and direction of a relationship between two variables.

Naturalistic Observation

Watching behavior in its natural setting without intervention; high realism, no causal claims.

Descriptive vs Inferential Statistics

Descriptive summarize data (mean, SD); inferential test whether results generalize to a population.

Informed Consent & IRB

Participants must knowingly agree to take part; an Institutional Review Board reviews ethics of studies.

Hindsight Bias

The 'I-knew-it-all-along' tendency to see outcomes as predictable after they occur; one reason intuition is not a substitute for research.

Overconfidence

Tendency to overestimate the accuracy of our knowledge and judgments; leads people to trust hunches over data.

Replication

Repeating a study with different participants or settings to see whether the basic finding holds; central to the reproducibility crisis debate.

Meta-Analysis

A statistical procedure that combines results of many studies on the same question to estimate an overall effect size.

Effect Size

A measure of how large a difference or relationship is, independent of sample size; complements statistical significance.

Statistical Significance (p < .05)

Result unlikely (less than 5% chance) to have occurred if the null hypothesis were true; does not by itself mean the effect is large or important.

Standard Deviation

Average distance of scores from the mean; a larger SD means more spread. In a normal curve about 68% of scores fall within 1 SD of the mean.

Skewed Distribution

An asymmetric distribution; a few extreme high scores pull the mean above the median (positive skew), extreme low scores pull it below (negative skew).

Illusory Correlation

Perceiving a relationship where none exists, often because we notice and remember confirming instances (e.g., 'full moon and strange behavior').

Regression Toward the Mean

Extreme scores tend to be followed by scores closer to the average; can make an ineffective intervention look like it worked.

Random Sampling vs Random Assignment

Random sampling selects participants so the sample represents the population (external validity); random assignment places them into conditions to equalize groups (internal validity).

Sampling Bias

A flawed sampling process that produces an unrepresentative sample, such as surveying only volunteers or only college students.

Wording Effects

Subtle changes in how a survey question is phrased can dramatically change responses ('aid to the needy' vs 'welfare').

Social Desirability Bias

Respondents answer in ways that make them look good rather than truthfully; a threat to self-report validity.

Hawthorne Effect

Participants change behavior simply because they know they are being observed.

Single-Blind Study

Only the participants are unaware of which condition they are in; controls placebo effects but not experimenter bias.

Debriefing

After a study, participants receive a full explanation, including any deception used; required by APA ethics.

Longitudinal vs Cross-Sectional

Longitudinal follows the same people over time (costly, attrition); cross-sectional compares different age groups at once (fast, cohort effects).