Causality and the experimental method

At the heart of psychology lies a beautifully simple question: What causes what? The experimental method gives us the clearest path to answering this question, and its elegance lies in its straightforward logic.

Causality is the relationship between cause and effect. When we say “X causes Y,” we mean that changes in X directly produce changes in Y. In psychology, establishing causality allows us to move beyond mere correlation and understand the mechanisms behind behavior.

The key requirement for causality is that we must demonstrate that one variable directly produces a change in another variable.

The experimental method is powerful precisely because of its simple logic. The basic formula involves three steps. First, change one thing, which is the Independent Variable or IV. Second, keep everything else the same by controlling all other variables. Third, measure what happens by observing changes in the Dependent Variable or DV.

The beautiful conclusion follows naturally. If the DV changes, and we’ve controlled everything else, then the change in the IV must have caused the change in the DV. That’s it. That’s the entire logic.

Teaching Tip 1: Start with the Logic: Before diving into terminology, help students grasp the fundamental reasoning. If I want to know whether caffeine improves memory, I need to change only the caffeine and see what happens to memory. If I change multiple things at once, I can’t know which one caused the effect.

Teaching Tip 2: Emphasize Control: The power of the experimental method isn’t in what we change, it’s in what we don’t change. Every variable we control strengthens our claim of causality.

Teaching Tip 3: Connect to Real Research: When teaching studies like Loftus and Palmer on leading questions and memory, or Bandura’s Bobo doll experiment on observational learning and aggression, highlight the beautiful simplicity. Identify the IV, which is the variable the researcher manipulated. Identify the DV, which is what they measured. Note the controls, which is everything they kept the same. Then draw the conclusion: because everything else was controlled, the IV caused the change in the DV.

The Three Essential Components: Help students remember these three pillars. First is manipulation, where the researcher deliberately changes the IV. Second is control, where all other variables are kept constant. Third is measurement, where the DV is carefully observed and recorded.

When all three are present, we can claim causality. When any are missing, we cannot.

Some students believe that correlation shows causation. This is incorrect. Only the experimental method establishes causality because only experiments control for alternative explanations.

Others think that any study with numbers shows causation. This is also incorrect. Surveys and correlational studies provide valuable data but cannot establish cause and effect.

Some confuse control with control group. This is partially correct. Control means keeping variables constant and may include a control group for comparison.

Making It Stick: Use this simple framework when analyzing any study. (i) What did they change? That’s the IV. (ii) What did they measure? That’s the DV. (iii) What did they control? Those are the other variables. (iv.) Can we claim causation? Only if it’s a true experiment.

The experimental method’s beauty lies in its logical simplicity. Change one variable, control all others, measure the outcome. If the outcome changes, you’ve found your cause. This simple logic is psychology’s most powerful tool for understanding the mechanisms of human behavior.

Here’s a powerpoint presentation that you can use for teaching a lesson on the true and quasi experiment.

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