Introduction Rater-based assessment has resulted in high cognitive demands for assessors within the education of health professionals. Rating quality may be influenced by the mental workload required of assessors to complete rating tasks. The objective of this review was to explore interventions or strategies aimed at measuring and reducing mental workload for improvement in assessment outcomes in health professions education.

Methods A critical narrative review was conducted for English-language articles using the databases PubMed, EMBASE, and Google Scholar from conception until November 2018. To be included, articles were eligible if they reported results of interventions aimed at measuring or reducing mental workload in rater-based assessment.

Results A total of six articles were included in the review. All studies were conducted in simulation settings (OSCEs or videotaped interactions). Of the four studies that measured mental workload, none found any reduction in mental workload as demonstrated by objective secondary task performance after interventions of assessor training or reductions in competency dimension assessment. Reductions in competency dimensions, however, did result in improvements in assessment quality across three studies.

Discussion The concept of mental workload in assessment in medical education needs further exploration, including investigation into valid measures of assessors’ mental workload. It appears that adjusting raters’ focus may be a valid strategy to improve assessment outcomes. Future research should be designed to inform how to best reduce load in assessments to improve quality, while balancing the type and quantity of data needed for judgments.