Mind-wandering is a broad term with no currently universal definition. According to McMillan, Kaufmann and Singer (2013) mind-wandering consists of 3 different subtypes: positive constructive daydreaming, guilty fear of failure, and poor attentional control. Whereas Smallwood and Schooler (2015) suggest that mind-wandering consists of thoughts that are task-unrelated and stimulus-independent. In general, a folk explanation of mind-wandering could be described as the experience of thoughts not remaining on a single topic for a long period of time, particularly when people are engaged in an attention-demanding task. One context in which mind-wandering often occurs is driving. This is because driving under optimal conditions becomes an almost automatic activity that can require minimal use of the task positive network, the brain network that is active when one is engaged in an attention-demanding activity. In situations where vigilance is low, people do not remember what happened in the surrounding environment because they are preoccupied with their thoughts. This is known as the decoupling hypothesis. Studies using event-related potentials (ERPs) have quantified the extent that mind-wandering reduces the cortical processing of the external environment. When thoughts are unrelated to the task at hand, the brain processes both task-relevant and unrelated sensory information in a less detailed manner. Mind-wandering appears to be a stable trait of people and a transient state. Studies have linked performance problems in the laboratory and in daily life. Mind-wandering has been associated with possible car accidents. Mind-wandering is also intimately linked to states of affect. Studies indicate that task-unrelated thoughts are common in people with low or depressed mood. Mind-wandering also occurs when a person is intoxicated via the consumption of alcohol. Studies have demonstrated a prospective bias to spontaneous thought because individuals tend to engage in more future than past related thoughts during mind-wandering. The default mode network is thought to be involved in mind-wandering and internally directed thought, although recent work has challenged this assumption. History The history of mind-wandering research dates back to 18th century England. British philosophers struggled to determine whether mind-wandering occurred in the mind or if an outside source caused it. In 1921, Varendonck published The Psychology of Day-Dreams, in which he traced his "'trains of thoughts' to identify their origins, most often irrelevant external influences". Wallas (1926) considered mind-wandering as an important aspect of his second stage of creative thought – incubation. It wasn't until the 1960s that the first documented studies were