Cognitive Psychology Experiments

Why This Matters

Cognitive psychology experiments form the foundation for everything you'll encounter in cognitive science. These studies reveal the mechanisms behind attention, memory encoding, learning, and social behavior, and they show up repeatedly on exams because they demonstrate core principles in action. When you understand why Sperling used partial report or what made Milgram's participants obey, you're grasping the architecture of the mind itself.

You're being tested on your ability to connect experimental methods to theoretical frameworks. Don't just memorize that Pavlov rang a bell; know that his work demonstrates associative learning and the difference between conditioned and unconditioned stimuli. Each experiment on this list illustrates a specific cognitive mechanism, and your job is to identify which principle each one proves.

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Attention and Cognitive Control

These experiments reveal how the brain manages competing information and why some processes override others. Automatic processing happens without conscious effort, while controlled processing requires deliberate attention. When they conflict, the results tell us a lot about how cognition is organized.

Stroop Effect Experiment

The Stroop task is one of the most replicated findings in cognitive psychology. Participants are shown color words printed in mismatched ink colors (e.g., the word "RED" printed in blue ink) and asked to name the ink color, not read the word. This turns out to be surprisingly hard.

• Automatic vs. controlled processing conflict: Reading is so well-practiced that it happens automatically, and it interferes with the slower, controlled process of naming the ink color. The result is longer reaction times and more errors on incongruent trials.
• Why reading wins: Reading is a skill most people have practiced for years, making it faster and more deeply automatized than color naming. Suppressing that automatic response takes real cognitive effort.
• What it measures: The Stroop task is widely used as a measure of executive function, specifically your ability to inhibit a dominant response. Difficulty on this task can indicate problems with cognitive flexibility and attentional control.

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Memory Systems and Encoding

Memory isn't a single system. It's a collection of specialized processes with different capacities and durations. These experiments map out sensory memory, working memory, and long-term memory, showing how information moves between them.

Sperling's Iconic Memory Experiment

Before Sperling's work (1960), researchers knew people could only report about 4-5 items from a briefly flashed display. But was that because they only saw 4-5 items, or because the rest faded before they could report them? Sperling's experiment answered this question.

• Iconic memory is a visual sensory store that holds a large amount of information but decays rapidly, within roughly 250-500 milliseconds.
• Partial report technique: Sperling flashed a grid of letters for about 50 ms, then played a tone cueing participants to report only one row. Participants could accurately report whichever row was cued, proving they had briefly stored the entire display.
• Why it matters: This established that sensory memory has high capacity but extremely short duration. The bottleneck isn't in what we perceive; it's in how quickly we can transfer that information to a more durable store.

Baddeley's Working Memory Model Experiments

Baddeley replaced the old idea of a single "short-term memory" with a multi-component system. His evidence came primarily from dual-task paradigms, where participants performed two tasks simultaneously.

• Multi-component architecture: The model includes the phonological loop (handles verbal and acoustic information), the visuospatial sketchpad (handles spatial and visual information), and the central executive (directs attention and coordinates the subsystems).
• The key finding: Two verbal tasks interfere with each other, and two spatial tasks interfere with each other, but a verbal task and a spatial task can run in parallel with minimal interference. This pattern only makes sense if separate subsystems handle each type of information.
• Practical impact: This work gave rise to cognitive load theory, which explains why, for example, reading dense text while listening to a lecture overwhelms the phonological loop and degrades performance on both tasks.

Ebbinghaus Forgetting Curve Experiment

Hermann Ebbinghaus used himself as his only participant and memorized lists of nonsense syllables (like "DAX" or "BUP") to strip away the influence of meaning and prior knowledge. This let him study pure retention.

• Exponential decay: Forgetting is steepest right after learning. Ebbinghaus found that most information is lost within the first hour, after which the rate of forgetting levels off considerably.
• The spacing effect: He also discovered that spreading study sessions out over time (distributed practice) produces far stronger retention than cramming everything into one session (massed practice). This remains one of the most robust findings in all of learning science.

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Memory Reconstruction and Reliability

Memory isn't a video recording. It's a reconstructive process vulnerable to distortion. These experiments demonstrate how post-event information and suggestive questioning can alter what we think we remember.

Loftus and Palmer's Car Crash Experiment

Participants watched a film of a car accident and then answered questions about it. The critical manipulation was a single verb in the question: "How fast were the cars going when they _____ each other?"

• Misinformation effect: Participants who heard "smashed" gave higher speed estimates than those who heard "contacted." Even more striking, those in the "smashed" condition were more likely to falsely report seeing broken glass in the film (there was none).
• Schema-driven reconstruction: The verb activated different schemas (expectations about what a "smash" looks like vs. a "contact"), and participants' memories were reconstructed to fit those schemas. Memory, in other words, is shaped by the framework we use to retrieve it.
• Real-world implications: This research transformed how courts and law enforcement think about eyewitness testimony and the wording of interview questions.

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Learning Mechanisms

How do organisms acquire new behaviors? These foundational experiments established two major learning paradigms: classical conditioning (learning through association) and operant conditioning (learning through consequences). Bandura then expanded the picture by showing that direct experience isn't always necessary.

Pavlov's Classical Conditioning Experiments

Pavlov noticed that his dogs began salivating not just to food, but to cues that predicted food. He turned this observation into a systematic research program on associative learning.

• The basic procedure: A neutral stimulus (bell) is repeatedly paired with an unconditioned stimulus (US; food, which naturally triggers salivation). After enough pairings, the bell alone becomes a conditioned stimulus (CS) that triggers a conditioned response (salivation).
• Extinction: If the CS is presented repeatedly without the US, the conditioned response gradually weakens and disappears.
• Generalization and discrimination: Organisms tend to respond to stimuli similar to the CS (generalization) but can learn to respond only to the specific CS and not to similar stimuli (discrimination).

Skinner's Operant Conditioning Experiments

While Pavlov studied involuntary reflexes, Skinner studied voluntary behavior. Using the Skinner box (an enclosed chamber with a lever or key and a food dispenser), he showed that animals adjust their behavior based on its consequences.

• Core principle: Behaviors followed by reinforcement increase in frequency; behaviors followed by punishment decrease.
• Reinforcement schedules produce different patterns of behavior. Variable-ratio schedules (reinforcement after an unpredictable number of responses) generate the highest, most persistent response rates. This is the same principle behind slot machines.
• A common confusion: Negative reinforcement is not punishment. Positive reinforcement adds something pleasant; negative reinforcement removes something unpleasant. Both increase the target behavior. Punishment, by contrast, decreases behavior.

Bandura's Bobo Doll Experiment

Bandura's experiment (1961) challenged the behaviorist assumption that learning requires direct reinforcement. Children watched an adult model interact with a large inflatable Bobo doll, either aggressively or non-aggressively.

• Observational learning: Children who watched the aggressive model later imitated specific aggressive behaviors toward the doll, even though they were never reinforced for doing so.
• Vicarious reinforcement: Later variations showed that children were more likely to imitate aggression when the model was rewarded for it and less likely when the model was punished. The children learned the behavior either way, but whether they performed it depended on observed consequences.
• Social learning theory bridges behaviorism and cognitivism by showing that internal cognitive processes (attention, memory, motivation) mediate between observing a behavior and reproducing it.

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Social Influence and Authority

These controversial experiments reveal how powerfully situations shape behavior, sometimes overriding personal values and moral judgment. They demonstrate obedience, conformity, and role adoption under social pressure.

Milgram Obedience Experiment

Milgram (1963) told participants they were in a "learning study" and instructed them to deliver increasingly intense electric shocks to a confederate (who was actually an actor and received no shocks) each time the confederate answered a question incorrectly.

• The finding: About 65% of participants went all the way to the maximum 450-volt shock when prompted by an experimenter in a lab coat, despite hearing the confederate's protests and apparent distress.
• Situational factors dramatically affected obedience rates. Obedience dropped when the participant was in the same room as the "victim," when the experimenter gave instructions by phone, or when other confederates refused to continue.
• Agentic state theory: Milgram proposed that people enter an "agentic state" in which they see themselves as agents carrying out someone else's wishes, shifting moral responsibility to the authority figure.

Stanford Prison Experiment

Zimbardo (1971) randomly assigned college students to play either "guards" or "prisoners" in a simulated prison in the basement of Stanford's psychology building. The study was planned for two weeks.

• Role adoption: Guards quickly began using authoritarian and sometimes abusive tactics. Prisoners became increasingly passive, anxious, and distressed. These behavioral changes emerged without any explicit instructions to act this way.
• Deindividuation: Uniforms, numbers instead of names, and assigned roles eroded individual identity, making it easier for participants to act in ways they normally wouldn't.
• Ethical concerns: The study was terminated after just six days due to the psychological harm being inflicted on participants. It's now discussed as much as a case study in research ethics as it is a study of social psychology. (It's also worth noting that the study has faced significant methodological criticisms, including small sample size and possible experimenter demand effects.)

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Quick Reference Table

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Self-Check Questions

1. Both Pavlov's and Skinner's experiments involve learning, but they differ in a fundamental way. What type of response does each study, and why does this distinction matter for understanding behavior modification?

2. If a question asks you to explain why eyewitness testimony is unreliable, which experiment provides the strongest evidence, and what specific mechanism does it demonstrate?

3. Compare Sperling's iconic memory experiment with Baddeley's working memory model. How do they address different stages of memory processing, and what methods did each use to isolate their target system?

4. The Milgram and Stanford Prison experiments both reveal the power of situations over individual behavior. What is the key difference in how social influence operated in each study?

5. A student claims that Bandura's Bobo Doll experiment proves the same thing as Skinner's operant conditioning research. How would you explain why this is incorrect, and what unique contribution does Bandura's work make to learning theory?