How is a natural experiment defined?

A natural experiment is characterized by the presence of an independent variable that occurs naturally, rather than being manipulated by the researcher. This means researchers take advantage of a pre-existing situation or event that divides participants into different groups based on varying levels of exposure to that independent variable. Such conditions allow for the investigation of causal relationships while maintaining a certain level of ecological validity since the experiment is grounded in real-world scenarios.

In contrast, a manipulated independent variable implies an experimenter-driven design where the researcher actively alters conditions to observe effects, which does not align with the concept of a natural experiment. Random assignment to conditions is typical of controlled experiments, which aim for an equal distribution of characteristics across groups to isolate the effect of the independent variable. Lastly, strictly controlled conditions refer to laboratory experiments that maintain a high level of control over variables to minimize extraneous influences, which is not applicable in the context of natural experiments that capitalize on naturally occurring variations.