The Milgram experiment used a controlled laboratory experiment as its research method. Conducted at Yale University between 1961 and 1963, Stanley Milgram designed a structured lab setting where he could manipulate specific variables and measure their effect on obedience to authority. This makes it a true experimental method, not merely an observation or survey.
Why It Qualifies as a Laboratory Experiment
A laboratory experiment has three defining features: it takes place in a controlled environment, the researcher manipulates one or more independent variables, and participants are measured on a dependent variable. Milgram’s study checks all three boxes.
The controlled environment was a lab at Yale, where every detail of the setup was standardized. The independent variables were the conditions Milgram changed across his 21 experimental variations, including the physical proximity between the participant and the person receiving “shocks,” the authority and directiveness of the experimenter, and whether peer pressure was present. The dependent variable was obedience, operationally defined as whether the participant continued administering shocks all the way to the maximum 450 volts.
Across all 21 conditions involving 740 participants, the overall rate of full obedience (progressing to maximum voltage) was 43.6%. By systematically changing one condition at a time, Milgram could isolate which factors made people more or less likely to obey.
How the Procedure Worked
Participants were recruited through newspaper ads and told they were taking part in a study about learning and memory. When they arrived at the lab, they met another person who appeared to be a fellow volunteer but was actually a confederate working with the research team. A rigged drawing ensured the real participant always ended up in the role of “teacher,” while the confederate always became the “learner.”
The participant was seated in front of a shock generator with switches labeled in 15-volt increments, starting at 15 volts and climbing to 450 volts. The learner was taken to an adjacent room and connected to what appeared to be electrodes. In reality, no shocks were ever delivered. The participant’s job was to test the learner on word pairs and deliver an increasingly powerful shock for every wrong answer.
As the voltage increased, the learner (following a script) began to cry out in pain. At 150 volts, the learner’s first protests were loud enough that nearly every participant paused and expressed reluctance to continue. This 150-volt mark turned out to be the critical decision point: 82.5% of participants who continued past it went all the way to 450 volts.
Standardized Prods as Experimental Controls
One element that made this a tightly controlled experiment was the use of scripted verbal prods. Whenever a participant hesitated or refused to continue, the experimenter responded with a sequence of four standardized prompts:
- Prod 1: “Please continue” or “Please go on.”
- Prod 2: “The experiment requires that you continue.”
- Prod 3: “It is absolutely essential that you continue.”
- Prod 4: “You have no other choice, you must go on.”
These prods were always delivered in order, escalating from a polite request to a direct command. If the participant still refused after the fourth prod, the experiment ended. This standardization ensured that every participant experienced the same level of pressure, which is essential for drawing valid comparisons across conditions.
What Milgram Changed Across Conditions
Milgram didn’t run just one experiment. He ran 21 variations, each changing a specific factor to see how it affected obedience. A large meta-analysis of these conditions identified eight factors that significantly influenced whether participants obeyed to the maximum voltage:
- Experimenter’s directiveness: A more commanding experimenter produced higher obedience.
- Experimenter’s legitimacy: When the authority figure seemed less credible, obedience dropped.
- Experimenter’s consistency: If two experimenters gave contradictory instructions, participants were more likely to stop.
- Group pressure to disobey: When other “teachers” (confederates) refused to continue, participants followed their lead.
- Proximity to the learner: The closer the participant was to the person being shocked, the harder it was to obey.
- Intimacy with the learner: Any personal connection reduced compliance.
- Indirectness of harm: When participants only had to assist while someone else pressed the switch, obedience increased.
- Distance from the experimenter: When the experimenter gave orders by phone rather than standing in the room, obedience fell sharply.
This systematic manipulation of variables is what separates a laboratory experiment from a simple demonstration. Milgram wasn’t just showing that people obey. He was measuring exactly which conditions increase or decrease obedience, and by how much.
Strengths and Limitations of This Method
The laboratory setting gave Milgram a level of control that would be impossible in a field study. Every participant heard the same scripted responses from the learner, received the same prods from the experimenter, and sat in front of the same shock generator. This makes the results highly replicable, and researchers have in fact replicated them. In 2009, psychologist Jerry Burger ran a modified version that capped shocks at 150 volts to meet modern ethical standards and found strikingly similar compliance rates.
The main criticism of this method is ecological validity. A lab at Yale, with a scientist in a gray coat giving instructions, is not a situation most people encounter in daily life. Critics have argued that participants may have behaved differently because they trusted that a prestigious university wouldn’t allow real harm. The artificial setting raises questions about whether the findings translate directly to real-world obedience, though the consistency of results across replications and cultural contexts suggests the underlying patterns are genuine.
There’s also the issue of deception. Participants were told the study was about learning, not obedience. They believed they were delivering real shocks. This level of deception is what makes the experiment powerful as a research tool but also what makes it ethically controversial. Modern institutional review boards would not approve the original protocol, which is why Burger’s 2009 replication introduced safeguards like screening out participants who might be psychologically vulnerable and stopping at the 150-volt threshold rather than allowing escalation to 450.