In an experiment, the control group is the set of participants who do not receive the treatment (the independent variable manipulation), serving as a baseline so researchers can compare results and conclude whether the treatment actually caused a change in the dependent variable.
A control group is the group in an experiment that does not receive the treatment. Everything else about their experience is kept identical to the experimental group. That's the whole point. If both groups are the same except for the independent variable, then any difference in the dependent variable must come from the treatment.
Think of it as the "compared to what?" group. Say a researcher claims a study app boosts test scores. Boosts them compared to what? Without a control group of participants who studied without the app, there's no baseline, and the researcher can't rule out other explanations (maybe everyone improves just from taking the test twice). In drug studies, the control group often gets a placebo, a fake treatment, so the researcher can separate the drug's real chemical effect from people's expectations. Combine a control group with random assignment and you have the core machinery that lets psychologists make cause-and-effect claims.
Control groups live in Topic 1.2 (Research Methods in Psychology) and Topic 1.3 (Defining Psychological Science: The Experimental Method), the science-practices backbone of the whole course. The experiment is the only research method that can establish causation, and a control group is what makes that possible. This concept also resurfaces in Unit 8: Topic 8.7 covers treatment of psychological disorders, and the only way researchers know a therapy or an antipsychotic drug actually works is by comparing treated patients against a placebo control group. On the exam, research methods isn't just one unit. The Evidence-Based Question (EBQ) and the research-design SAQ both expect you to read a study, spot whether it has a control group, and explain what that means for the conclusions you can draw.
Keep studying AP Psychology Unit 1
Experimental Group (Unit 1)
The control group only makes sense as half of a pair. The experimental group gets the independent variable, the control group doesn't, and the difference between their outcomes is the experiment's actual finding.
Independent and Dependent Variables (Unit 1)
The control group is defined by the independent variable. It's the level where the manipulation is absent. Both groups are measured on the same dependent variable, which is how you see whether the IV mattered.
Psychoactive Drugs and Neural Transmission (Unit 1)
Topic 1.3 explains how drugs act as agonists, antagonists, or reuptake inhibitors. Proving any of that requires drug trials where a control group gets a placebo, so the chemical effect can be separated from expectation effects.
Treatment of Psychological Disorders (Unit 8)
Topic 8.7 asks how we know therapies like CBT or antipsychotic medications are effective. The answer runs straight back to Unit 1. Outcome studies compare treated groups to control groups, often using placebos and double-blind procedures.
Multiple-choice questions hit this term directly with stems like "What are control groups primarily used for in experimental research?" The expected answer is always some version of providing a baseline for comparison so the effect of the independent variable can be isolated. The bigger payoff is in the free-response section. The 2024 SAQ described Professor Gonzalez testing whether yellow paper improves memory for a course description, and the 2024 EBQ featured Dr. Dawson comparing students who read motivational statements with students who read neutral statements. In scenarios like these, you need to identify which group is the control (the white-paper group, the neutral-statement group) and explain why it's there. You may also be asked to design a study yourself, and forgetting to include a control group is one of the fastest ways to lose that point.
The experimental group receives the treatment (the independent variable); the control group does not. Students mix these up under time pressure, especially when the "control" condition still involves doing something, like reading neutral statements instead of motivational ones. The test is simple. Ask which group experiences the thing the researcher is studying. That's the experimental group. The other group, held constant as the baseline, is the control.
The control group does not receive the treatment and serves as the baseline that the experimental group is compared against.
Without a control group, you cannot conclude that the independent variable caused the change in the dependent variable.
In drug and therapy studies, the control group often receives a placebo so researchers can separate real treatment effects from participants' expectations.
Random assignment puts participants into control and experimental groups by chance, which keeps the two groups equivalent before the treatment starts.
Control groups connect Unit 1 research methods to Unit 8, because evidence that treatments like CBT or antipsychotics work comes from controlled outcome studies.
On FRQs, identify the control group in the scenario by name (for example, "the students who read neutral statements") rather than just saying "the control group."
It's the group in an experiment that does not receive the treatment. It acts as a baseline, so researchers can compare it to the experimental group and determine whether the independent variable caused any change in the dependent variable.
No. Control groups often get a placebo (like a sugar pill) or a neutral version of the task, such as reading neutral statements in the 2024 EBQ scenario. The point is they don't get the actual treatment being tested, not that they sit around doing nothing.
The experimental group receives the independent variable manipulation; the control group does not. Comparing the two groups' scores on the dependent variable is how the experiment answers its question.
No, they're separate tools that work together. Random assignment is how participants get sorted into groups by chance, which makes the groups equivalent at the start. The control group is one of the groups itself, the baseline condition.
Because people often improve just from believing they're being treated. Giving the control group a placebo lets researchers subtract that expectation effect and see whether the drug's effect on neurotransmitters, like an agonist or reuptake inhibitor, actually changes behavior.