The Uncontrollable Mind: The Relationship between Mind Wandering and Thought Suppression Failure.

Intrusion of unwanted thoughts (IUTs) is supposed to occur during mind wandering when mental resource is of short. However, few studies, if any, have empirically tested the relation between IUTs and mind wandering. A typical thought suppression paradigm, the white bear task, and mind wandering paradigm were applied to test the relationship between mind wandering and IUTs. In addition, we test the relationships between two individual traits, working memory capacities (WMC) and mindfulness traits and mind wandering or IUTs. In experiment 1, we found participants who have more daydreams (i.e., the frequency of shift in thoughts) at rest were prone to have IUTs. In experiment 2, participants’ tendency toward mind wandering was further reduced to different degrees by instructing them to focus on different targets (participants’ own breathes or a mental object) while doing thought suppression task. It was found that, compared to focus-object group, focusing-breath group, who had fewer mind wandering, did had fewer IUTs. In addition, results showed that relationships between two individuals’ traits and mind wandering or IUTs would change with different focusing targets. In focused-breath group, participants mind wandering and IUTs were negatively correlated with their mindfulness trait but were not correlated with WMC; whereas in focused-object group, their mind wandering and IUTs were negatively correlated with their WMC but were not correlated with their mindfulness trait. This study, for the first time, confirmed the conjectured relationship between mind wandering, both daydreaming and task-unrelated one, and IUTs. It also revealed that participants’ performance on thought suppression task was influenced by individuals’ WMCs and mindfulness traits in an opposite way, depending on the strategy they used to control mind wandering.