AP Psych SUPER ALL UNITS Combined List 2025

hindsight bias

The tendency to believe, after learning an outcome, that one would have foreseen it (AKA the I-knew-it-all-along phenomenon).

critical thinking

Mental effort that does not blindly accept arguments and conclusions, but instead examines assumptions, assesses the sources, discerns hidden biases, and evaluates evidence and conclusions.

peer reviews

Scientific experts who evaluate a research article's theory, originality, and accuracy.

overconfidence

The tendency to be more self-assured than correct—to overestimate the accuracy of our beliefs and judgments.

theory

An explanation using an integrated set of principles that organizes observations and predicts behaviors or events.

hypothesis

A testable prediction, often implied by a theory.

falsifiability

The possibility that an idea, hypothesis, or theory can be disproven by observation or experiment.

operational definition

A carefully worded statement of the exact procedures used in a research study. These make vague or ill-defined concepts more measurable (AKA operationalization).

replication

Repeating the essence of a research study, usually with different participants in different situations, to see whether the basic finding can be reproduced.

case study

A non-experimental technique in which an individual or group is studied in depth (using interviews) in the hope of revealing universal principles.

naturalistic observation

A non-experimental technique of observing and recording behavior in naturally occurring situations without trying to manipulate and control the situation.

survey

A non-experimental technique for obtaining the self-reported attitudes or behaviors of people, usually by questioning a representative, random sample of the group.

social desirability bias

Skewing of data that results from people responding in ways that they think the researcher expects or wishes.

self-report bias

Skewing of data that results from people reporting their behavior inaccurately.

sampling bias

A flawed selection process that produces a less than representative sample (when parts of the target population are over or under represented).

sample

Part of a population.

population

All those in a group being studied, from which random samples may be drawn.

random sample

A sample that fairly represents a population because each member has an equal chance of inclusion.

convenience sample

A non-probability sampling method (i.e. not random) where participants are selected for inclusion in the sample because they are the easiest for the researcher to access.

framing

The way an issue or question is phrased; wording or presentation can significantly affect decisions and judgments.

correlation

A measure of the extent to which two variables change together, and thus of how either variable predicts the other (NOT about cause and effect).

scatterplot

A graphed cluster of dots, each of which represents the values of two variables. The slope of the points suggests the direction of the relationship between the two variables, and the amount of scatter suggests the strength of the correlation (less scatter indicates higher correlation).

positive correlation

A relationship between two variables in which both rise or fall together.

negative correlation

A relationship between two variables in which the value of one variable increases as the value of the other decreases.

correlation coefficient

A measurement or mathematical expression of the relationship between two variables (often symbolized as "r"). A range from -1 to +1 is used to show the strength of a relationship between the two (but NOT cause and effect). The closer to +1 or -1, the stronger the relationship.

variable

Anything that can change and is feasible and ethical to measure.

directionality problem

In correlational research, the situation in which it is known that two variables are related although it is not known which variable is having the primary influence on the other.

third variable problem

An undiscovered causal variable. When a relationship is found between variables x and y, variable x may be mistakenly thought to be caused by y. However, the cause of y may be a hidden variable z that is correlated with variable x.

illusory correlation

Perceiving a relationship where none exists or perceiving a stronger-than-actual relationship.

regression toward the mean

The tendency for extreme or unusual scores or events to fall back toward the average.

experiment

A research method in which an investigator manipulates one or more factors (independent variables) to observe the effects on some behavior or mental process (the dependent variable). By random assignment of participants, the researcher aims to control other relevant variables.

experimental group

In experiments, the group that DOES receive the independent variable (exposed to the treatment) being tested.

control group

In experiments, the group that DOES NOT receive the independent variable (NOT exposed to the treatment) being tested.

random assignment

Assigning participants to experimental and control conditions by chance (like "drawing names out of a hat"), thus minimizing preexisting differences between those assigned to the different groups.

single blind procedure

An experimental procedure in which the research participants are ignorant about whether they have received the treatment or the placebo.

double blind procedure

An experimental procedure in which both the research participants and the research staff are ignorant about whether the research participants have received the treatment or a placebo; commonly used in drug-evaluation studies.

placebo

An inert substance or condition (which the recipient assumes is or could be genuine) used to compare the effect of an actual substance (the active agent).

placebo effect

Any experimental result that seems to be a consequence of an inert substance or condition, which the recipient assumes is an active agent; any experimental results that are caused by expectations alone.

dependent variable

In an experiment, the outcome factor, this is the variable in an experiment that may change in response to manipulations of another variable; often identified by the value "y."

confounding variables

In an experiment, factors other than the independent variable that might produce an effect in an experiment (AKA threats to validity). When properly controlled, these are known as control variables.

independent variable

In an experiment, the factor or condition in an experiment that is manipulated so that its effects may be observed; often identified by "x," this is the variable whose effect is being studied.

experimenter bias

A skewing or data or results caused when researchers unintentionally influence those results to confirm their own beliefs.

validity

The extent to which a test or experiment measures or predicts what it is supposed to.

quantitative research

A research method that relies on numerical data.

qualitative research

A research method that relies on in-depth, narrative or descriptive data that are not translated into numbers.

Likert scale

A rating system (as in a span of 1-5) used in research to evaluate attitudes, opinions and perceptions by making them more measurable (quantitative).

descriptive statistics

Numerical data used to measure and describe characteristics of groups (including measures of central tendency and variation).

histogram

A bar graph depicting a frequency distribution.

mode

The most frequently occurring score(s) in a distribution (a measure of central tendency).

mean

The arithmetic average of a distribution, obtained by adding the scores and then dividing by the number of scores (a measure of central tendency).

percentile rank

The percentage of scores that are lower than a given score.

skewed distribution

A representation of scores that lack symmetry around their average value.

range

The difference between the highest and lowest scores in a distribution.

bimodal distribution

A frequency distribution having two different values that are heavily populated with cases

median

The middle score in a distribution; half the scores are above it and half are below it (a measure of central tendency).

standard deviation

A computed measure of how much scores vary around the mean score

normal curve

A symmetrical, bell-shaped curve that describes the distribution of many types of data; most scores fall near the mean (about 68% fall within one standard deviation of it) and fewer and fewer near the extremes (AKA normal distribution).

meta-analysis

A statistical procedure for analyzing the results of multiple studies to reach an overall conclusion.

null hypothesis

A prediction that there is NO relationship between two variables.

alternative hypothesis

A prediction that there Is a relationship between two variables.

statistical significance

A numerical statement of how likely it is that a result (such as differences between samples) has occurred by chance - assuming there is no difference between the populations being studied; this would show that the IV made a real difference in the DV. (AKA significant difference).

effect size

The strength of a relationship between two variables. The larger this is the more one variable can be explained by the other.

informed consent

An ethical principle requiring that research participants be told enough to enable them to choose whether they wish to participate

debriefing

The post-experimental explanation of a study, including its purpose and any deceptions, to its participants

informed assent

A method for including minors in research. The process involves explaining the trial to the minor in a way they can understand, and encouraging them to ask questions. If the minor signals willingness to participate, consent must then be obtained from the minor's parent or guardian.

inferential statistics

Numerical data that allow one to generalize from sample data the probability of something being true of a population.

institutional review board (IRB)

A committee at each college/university where research is conducted to review every experiment for ethics and methodology.

p-value

The probability that the difference between two samples could occur by chance alone

generalizability

The extent to which research results apply to a range of individuals not included in the study.

research confederate

An actor who participates in a psychological experiment pretending to be a subject but in actuality working for the researcher (also known as a "stooge").

biological psychology

A branch of psychology concerned with the links between biology (genes, neurons, hormones, etc.) and behavior.

neuron

A nerve cell; the basic building block of the nervous system

nervous system

The body's speedy, electrochemical communication network, consisting of all the nerve cells of the peripheral and central nervous systems

central nervous system (CNS)

The brain and spinal cord.

peripheral nervous system (PNS)

The sensory and motor neurons that connect the central nervous system to the rest of the body

nerves

Bundled axons that form neural "cables" connecting the central nervous system with muscles, glands, and sense organs.

sensory neurons

Neurons that carry incoming information from the sensory receptors to the brain and spinal cord (AKA afferent neurons).

motor neurons

Neurons that carry outgoing information from the brain and spinal cord to the muscles and glands (AKA Efferent neurons).

interneurons

Neurons within the brain and spinal cord that communicate internally and intervene between the sensory inputs and motor outputs.

somatic nervous system

The division of the peripheral nervous system that controls the body's skeletal muscles.

autonomic nervous system

The part of the peripheral nervous system that controls the glands and the muscles of the internal organs (such as the heart). Its sympathetic division arouses; its parasympathetic division calms.

sympathetic nervous system

The division of the autonomic nervous system that arouses the body, mobilizing its energy in stressful situations (fight or flight).

parasympathetic nervous system

The division of the autonomic nervous system that calms the body, conserving its energy (rest and digest).

reflex

A simple, automatic response to a sensory stimulus, such as the knee-jerk response.

myelin sheath

A fatty tissue layer encasing the axons of some neurons; enables vastly greater transmission speed as neural impulses travel down the axon; a lack of this is associated with Multiple Sclerosis.

action potential

A neural impulse; a brief electrical charge that travels down an axon

neurotransmitters

Chemical messengers that cross the synaptic gaps between neurons. When released by the sending neuron, these chemicals travel across the synapse and bind to receptor sites on the receiving neuron, influencing whether that neuron will generate a neural impulse.

reuptake

A neurotransmitter's reabsorption by the sending neuron

endorphins

Think "morphine within"—natural, opiate-like neurotransmitters linked to pain control and to pleasure.

hormones

Chemical messengers that are manufactured by the endocrine glands, travel through the bloodstream, and affect other tissues

pituitary gland

The endocrine system's most influential gland ("the MASTER gland'). Under the influence of the hypothalamus, regulates growth and controls other endocrine glands.

lesion

Tissue destruction. It can occur naturally (via disease or injury) or experimentally.

electroencephalogram (EEG)

An amplified recording of the waves of electrical activity that sweep across the brain's surface. These waves are measured by electrodes placed on the scalp.

fMRI (functional MRI)

A technique for revealing blood flow and, therefore, brain activity by comparing successive brain scans.

brainstem

The oldest part and central core of the brain, beginning where the spinal cord swells as it enters the skull; the brainstem is responsible for automatic survival functions

medulla

The base of the brainstem; controls heartbeat and breathing

reticular activating system

A nerve network in the brainstem that plays an important role in controlling arousal

thalamus

The brain's sensory switchboard, located on top of the brainstem; it directs messages to the sensory receiving areas in the cortex and transmits replies to the cerebellum and medulla - all senses, but smell are processed here.

cerebellum

The "little brain" at the rear of the brainstem; functions include processing sensory input and coordinating movement output an balance

limbic system

The doughnut-shaped neural system (including the hippocampus, amygdala, and hypothalamus) located below the cerebral hemispheres; associated with emotions and drives