Because psychology is a science, its findings rely on the systematic application of the scientific method. Researchers typically begin by forming a hypothesis, then designing a study, collecting data, analyzing their results, and drawing conclusions. This structured process ensures that claims about behavior are replicable and not simply based on intuition or anecdote. At the heart of any experiment are two key variables: the independent variable, which is the factor the researcher manipulates or changes and is assumed to be the cause, and the dependent variable, which is the outcome that is measured and may change in response.
A major threat to valid conclusions is the confounding variable, an uncontrolled factor that may also influence the dependent variable, making it difficult to determine whether changes are truly caused by the independent variable. To minimize such threats, researchers use random assignment, ensuring that each participant has an equal chance of being placed in any condition, which helps control for pre-existing differences between groups. Another safeguard is the double-blind study, in which neither the participants nor the researchers interacting with them know who is in the experimental versus control group, thereby reducing bias. Participants' expectations can also affect outcomes, as illustrated by the placebo effect, in which people show improvement simply because they believe they are receiving treatment, even when the treatment is inert.
One of the most important distinctions in psychological research is the difference between correlation and causation. Two variables may be related, or change together, without one causing the other; only well-controlled experiments can establish true causation. For this reason, psychologists are cautious about interpreting correlational findings as evidence that one variable produces another, and they explicitly design experiments to test causal claims.