Abstract
The ability to control one’s thoughts is important for mental wellbeing, attention, focus, future planning and ideation. While there is a long history of research into thought control, the inherent subjectivity of thoughts has made objective investigation, and thus mechanistic understanding difficult. Here, we report a novel method to empirically investigate thought control success and failure by objectively measuring the sensory strength of visual thoughts. We use the perceptual illusion binocular rivalry to assess emergent images in mind during two common thought control strategies: thought suppression and thought substitution. Thought suppression was ineffective, suppressed thoughts primed subsequent rivalry dominance at the same level as intentionally imagined thoughts. This priming effect was disrupted by concurrent uniform luminance and changes in retinotopic location, suggesting early visual representations/traces. While individuals showed some metacognition of thought suppression, strikingly, the perceptual effects remained even when thoughts were reported as successfully suppressed, indicating these thoughts may exist outside of reportable awareness. In contrast, thought substitution was more effective in controlling the perceptual effects and showed good metacognition. A thought control index predicted greater levels of trait mindfulness, while high levels of anxiety and schizotypy were related to poor thought control. Overall, our findings offer a novel method to track thoughts before and after they emerge into awareness and suggest that non-reportable and involuntary thoughts form visual representations pivotal to thought control failure.