The act or process of discriminating between genuine memories that are acquired through perception from external reality and apparent memories that are generated internally by imagination. It tends to break down in schizophrenia, delusional disorder, Alzheimer's disease, and other mental disorders characterized by hallucinations, delusions, and dementia, and it is temporarily disrupted by intoxication with some types of drugs, especially hallucinogens. Research into constructive memory has shown that the sources of many memories are neither purely external nor purely internal, and the distinction between external and internal memory sources is therefore considered relative rather than absolute. Reality monitoring is a form of metacognition that was named in 1981 by the US psychologists Marcia K. Johnson (born 1943) and Carol L. Raye, who were also the first to study it systematically. The term is widely used in cognitive psychology and is closely related to reality testing in clinical psychology. See also déjà vu, eyewitness misinformation effect, false memory, paramnesia (1), Piaget kidnapping memory, recovered memory, source memory.