A confederate in psychology is a person who appears to be a regular participant in an experiment but is actually working with the researcher. Their behavior is planned and rehearsed ahead of time, and the real participants have no idea the person next to them is part of the setup. Confederates allow researchers to create specific social situations and observe how people genuinely respond.
How Confederates Work in Experiments
The core idea is deception. A confederate pretends to be just another volunteer, but every word they say and every action they take follows a script designed by the researcher. This lets the experimenter control one side of a social interaction while measuring the real participant’s natural reaction. The term “stooge” is sometimes used interchangeably with confederate, though “confederate” is the standard in modern psychology.
Confederates differ from research assistants in an important way. A research assistant openly works for the study and participants know it. A confederate’s entire purpose depends on the real participant not knowing they’re part of the experiment. The moment a participant suspects someone is a plant, the data from that session becomes unreliable, because the participant stops behaving naturally.
The Asch Conformity Experiment
One of the most famous uses of confederates comes from Solomon Asch’s conformity studies in the 1950s. Asch brought people into a lab for what seemed like a simple visual task: look at a line and match it to one of three reference lines of different lengths. The correct answer was obvious. But sitting in the room were six to eight confederates who had been told to give the wrong answer out loud before the real participant had a chance to respond.
The real participant sat near the end of the group, hearing person after person confidently choose a line that was clearly incorrect. The question wasn’t whether people could judge line lengths. It was whether social pressure from a group of strangers would push someone to abandon what their own eyes told them. A striking number of participants went along with the group’s wrong answer at least some of the time. Without confederates creating that unanimous, confident, incorrect consensus, there would have been no way to study conformity this precisely.
The Milgram Obedience Study
Stanley Milgram’s obedience experiments used confederates in an even more elaborate way. Real participants were told they were “teachers” in a learning study. Their job was to administer an electric shock to a “learner” every time he got a question wrong, increasing the voltage each time. The learner was a confederate. No real shocks were ever delivered.
The confederate followed a carefully scripted sequence of responses. At 75 volts, participants heard a small grunt through the wall. The grunts grew louder with each shock. At 150 volts, the confederate yelled that he wanted to stop and mentioned a heart condition he’d brought up before the experiment began. After 300 volts, the confederate refused to answer any more questions. After 330 volts, there was only silence, implying the person on the other side of the wall might be unconscious or worse.
In some versions of the experiment, a second confederate played another “teacher” who modeled refusal. This confederate showed hesitation at 75 volts, expressed doubt at 90 volts, and eventually pushed back from the table and refused to continue. Then the real participant had to decide: keep going, or follow the example of someone who said no? By scripting these moments precisely, Milgram could measure how authority and peer behavior each influenced obedience.
Why Deception Is Necessary
Confederates exist because many of the most important questions in psychology involve spontaneous human reactions to social pressure, emergencies, or authority. You can’t study how people respond to a group of strangers giving wrong answers if those strangers are actually giving wrong answers by accident. You can’t study obedience to harmful orders if the participant knows no one is really being hurt. The controlled deception is what makes the measurement possible.
This creates a tension with research ethics. Participants are being lied to, sometimes in ways that cause real stress. Modern research ethics boards require that any study using confederates justify the deception, minimize psychological harm, and include a thorough debriefing afterward where participants learn what actually happened and why. The ethical scrutiny is significantly stricter now than it was during the Milgram era.
When Participants Get Suspicious
The biggest practical risk with confederates is that participants figure out something is off. If a confederate’s acting is unconvincing, or if the scenario feels staged, the participant may change their behavior in ways that have nothing to do with the variable being studied. Research on eyewitness memory has shown that the number of confederates present affects how people respond: participants gave fewer correct answers and felt less confident when three confederates were present compared to one. But those effects only hold if participants genuinely believe the confederates are real people giving their honest opinions.
Researchers take this seriously. Confederates are typically trained extensively, and sessions where a participant reports suspicion are often flagged or excluded from the final data.
Virtual Confederates in Modern Research
Running studies with human confederates is expensive, hard to standardize, and ethically complicated. A growing area of research replaces human confederates with virtual agents in immersive virtual reality environments. Researchers have replicated Asch’s conformity experiment using computer-generated characters, and participants still showed a tendency to go along with the group’s wrong answers, even when they knew the other “people” in the room were virtual.
One study placed participants in an immersive virtual environment with six virtual agents who gave incorrect responses, just as Asch’s original confederates did. The participants were led to believe these agents were controlled by other real people. This approach gives researchers precise control over variables like eye contact, tone of voice, and group size, while avoiding the inconsistency that comes with human actors performing the same script dozens or hundreds of times. It also sidesteps some of the ethical concerns around face-to-face deception, though it introduces new questions about whether virtual social pressure operates the same way real social pressure does.