AP Psychology · Unit 1
AP Psychology Unit 1: Scientific Foundations of Psychology
Unit 1 is the vocabulary unit everyone underestimates. It sets up the perspectives you'll reference all year and the research-methods language that shows up in the free-response question almost every single exam.
Below is every core term, written the way I'd explain it out loud in class: a definition you can actually parse, plus one concrete example so the idea sticks to something real.
Study tip
If you can label the independent variable, dependent variable, and control group in any study description, you've already secured most of the research-methods points on the exam.
21 terms, defined
Introspection
Looking inward and reporting on your own conscious thoughts, feelings, and sensations — psychology's earliest research method.
Example: Wundt's participants sipping coffee and describing the exact sequence of sensations they noticed.
Structuralism
An early school of thought that tried to break consciousness down into its most basic elements, the way chemistry breaks matter into atoms.
Example: Titchener asking participants to describe an apple purely as color, weight, and texture — never as 'an apple.'
Functionalism
An early school of thought focused on the purpose of mental processes — what behaviors and thoughts do for survival — rather than their parts.
Example: William James asking why fear is useful instead of what fear is made of.
Biological perspective
Explains behavior through genetics, brain structures, neurotransmitters, and hormones.
Example: Attributing depression partly to low serotonin activity rather than only to life events.
Behavioral perspective
Explains behavior as learned responses shaped by rewards, punishments, and associations in the environment.
Example: A student studying harder because good grades have consistently earned praise.
Cognitive perspective
Explains behavior through how people take in, store, interpret, and retrieve information.
Example: Two people leaving the same meeting with different memories because they focused on different details.
Humanistic perspective
Emphasizes free will, personal growth, and the drive to reach one's full potential.
Example: A therapist offering unconditional positive regard so a client can explore who they want to become.
Psychodynamic perspective
Explains behavior through unconscious motives, internal conflict, and early childhood experience.
Example: Interpreting a persistent fear of commitment as rooted in an early loss.
Sociocultural perspective
Explains behavior through the influence of culture, social norms, and group membership.
Example: Why direct eye contact reads as confident in one culture and disrespectful in another.
Hypothesis
A testable, falsifiable prediction about the relationship between two variables.
Example: 'Students who sleep 8 hours score higher on a memory test than students who sleep 4 hours.'
Independent variable
The variable the researcher deliberately manipulates to see what effect it has.
Example: The amount of sleep participants are assigned to get.
Dependent variable
The outcome the researcher measures — it depends on the independent variable.
Example: The number of words recalled on the memory test.
Operational definition
A precise statement of how a variable is measured or manipulated in a specific study.
Example: Defining 'stress' as a score above 20 on the Perceived Stress Scale, not just 'feeling overwhelmed.'
Random assignment
Placing participants into experimental groups by chance so pre-existing differences spread out evenly.
Example: Drawing names to decide who gets the 8-hour and who gets the 4-hour sleep condition.
Random sample
A sample in which every member of the population has an equal chance of being selected, making results generalizable.
Example: Pulling 200 student ID numbers at random from the full enrollment list.
Confounding variable
An uncontrolled third factor that could explain the results instead of the independent variable.
Example: If the 8-hour sleep group also happened to be the honors class, ability is confounded with sleep.
Placebo effect
Improvement caused by a participant's expectations rather than the treatment itself.
Example: Feeling more alert after a sugar pill you were told was caffeine.
Double-blind procedure
A design in which neither participants nor the researchers interacting with them know who is in which condition.
Example: A drug trial where the nurse handing out pills doesn't know which are active.
Correlation coefficient
A number from -1.00 to +1.00 describing the strength and direction of a relationship between two variables. It never proves causation.
Example: Ice cream sales and drowning deaths correlate at about +.70 — because both rise with summer heat.
Informed consent
Participants must be told enough about a study to freely decide whether to take part.
Example: Signing a form describing the tasks, time commitment, and right to withdraw at any point.
Debriefing
Fully explaining a study's true purpose, including any deception, after participation ends.
Example: Telling participants the 'other student' who criticized them was actually a confederate.
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