Mind wandering occurs when one’s attention shifts from its current thoughts, which is usually focused on an external task, to internal self-generated thoughts that are unrelated to the task at hand. Several studies have shown a link between working memory and mind wandering. Researchers have theorized that perceptual decoupling plays a role in mind wandering. Perceptual decoupling is an attentional shift and occurs when the mind starts to wander to self-generated thoughts and therefore becomes disengaged from the external task it was previously focusing on. Perceptual decoupling exhibits a shift of cognitive focus from extrinsic to intrinsic inputs and is accompanied by a reduction of attention of the external task. Researchers have also found that self-generated thoughts that have been reported to occur during mind wandering are frequently associated with episodic thought and emotion. The content of self-generated thoughts during mind wandering are usually focused on events that have occurred at a distinct time period such as the past or future. These kinds of thoughts are believed to depend on episodic memory processes in order to create this mental content. This shows that the episodic memory system plays a partial role in mind wandering when it comes to the creation of certain self-generated thoughts. Emotion has also been found to bring about mind wandering and self-generated thoughts. Studies have found that those with dysphoria have a higher chance of mind wandering. It has also been discovered that people are more likely to mind wander when their mood is low. This shows that emotion and mood play a role in the occurrence of mind wandering. In addition, executive control has been found to be a factor in mind wandering. Individuals who have high cognitive control have the ability to limit mind wandering when the external task is demanding. On the other hand, these same individuals are likely to experience an increase in mind wandering when the task is less challenging. This shows that the occurrence of mind wandering in those who exhibit a greater degree of executive control varies based on how demanding they believe an external task to be.