The psychological construct of memory illustrates why clear conceptual definitions are essential for measurement. Broadly aiming to measure memory leaves a researcher unable to decide whether participants should recall vocabulary words, recognize photographs, or remember a future action. Because memory actually consists of multiple semi-independent systems, a precise definition is required to guide measurement decisions. For example, explicitly defining the construct as long-term episodic memory clarifies that the researcher should use a task involving the recall of past experiences, such as remembering a previously learned list of words, rather than tasks measuring other memory systems.