Bruxism during the day. The ICDS-R defined sleep bruxism as "a stereotyped movement disorder characterized by grinding or clenching of the teeth during sleep", classifying it as a parasomnia. The second edition (ICSD-2) however reclassified bruxism to a "sleep related movement disorder" rather than a parasomnia. Alternatively, bruxism can be divided into "primary bruxism" (also termed "idiopathic bruxism"), where the disorder is not related to any other medical condition, or "secondary bruxism", where the disorder is associated with other medical conditions. Secondary bruxism includes iatrogenic causes, such as the side effect of prescribed medications. Another source divides the causes of bruxism
Involuntary memory diary method was also applied to the study of involuntary memory chaining. The main hypothesis was that chaining would also occur on autobiographical memory tasks. Participants were asked to report the presence of involuntary memories while performing an autobiographical memory task. Results showed that participants did experience involuntary memory recall when they were recalling the past deliberately (also known as voluntary memory). This implies that involuntary memory production occurs as a product of chaining from voluntary memory—deliberate recall of the past. A common question in the study of involuntary memory is related to priming; what is it that activates such