2.2 Looking for Causes: Experimental Research

Independent and Dependent Variables

• Experiment's purpose:
• how X (independent variable) affects Y (dependent variable).
• In psychology, dependent variable is usually some aspect of subjects' behavior

Experimental and Control Groups

• The two groups are alike in all respects (only on dimensions relevant to dependent variable) except for the variation created by the manipulation of the independent variable.
• Any differences between the two groups on the dependent variable must be due to the manipulation of the independent variable.

Extraneous Variables

• Extraneous variables can lead to confounding of variables (can't tell which is having effect) can result
• Need to be able to foresee these and control them to avoid confoundings. Ex. of safeguard is random assignment

Variations in Designing Experiments

• * Can use one group of subjects who serve as their own control group. Effects of X are evaluated by exposing single group to two conditions: experimental condition and control condition
• * Can manipulate more than 1 independent variable or measure more than one dependent variable in a single experiment. Main advantage is see whether 2 variables interact

Experimental Research Pros & Cons

• Advantage: Conclusions about cause-and-effect relationships between variables
• Limitations:
• Experiments are artificial - doubts can arise about applicability to world outside the lab
• Can't be used to explore some research questions due to ethical concerns or practicality