Occasionally, during the stream of thought, people report experiencing no mental content or being unable to access any content, a mental state termed mind-blanking (MB). While MB appears to be a ubiquitous component of our mental lives, there is currently no systematic characterisation of how often MB occurs and under what conditions. The present preregistered systematic review and meta-analysis aimed to determine how often MB is reported in experience-sampling studies. Our search strategy yielded a sample of 59 studies, probing mental reports for more than 8500 participants. Using Bayesian linear modelling, we estimated the meta-analytic MB report rate at 10% of total experience sampling. We did not find any evidence for an effect of experience-sampling parameters on MB report rates. However, we identified that low arousal was associated with higher MB report frequency. Additionally, and contrary to the established literature, ADHD MB rates did not differ from our normative, baseline MB rate. Finally, using our meta-analytically derived posterior estimate, we simulated synthetic experience-sampling studies to determine appropriate sample sizes. In doing so, we provide heuristic sample-size recommendations to ensure high statistical power in prospective investigations. We recommend that prospective experience-sampling studies include 35 participants and 50 probes per participant, which should provide over 95% power to detect medium-sized effects. Overall, the present meta-analysis suggests that MB is fundamentally an infrequent mental state, yet its inclusion in experience-sampling paradigms provides accuracy and granularity into the full scope of mental states during spontaneous thinking.
Boulakis et al. (Thu,) studied this question.