Fluid intelligence correlates with working memory capacity for both real-world objects and simple-feature stimuli

• Visual working memory for real-world objects is correlated with fluid intelligence. • Crystallized intelligence is not correlated with visual working memory capacity. • Working memory for features and objects may share cognitive processes related to fluid intelligence. Previous research has shown that individual differences in visual working memory performance strongly correlate with measures of fluid intelligence. In these studies, visual working memory was assessed using simple feature stimuli, such as oriented lines or colored squares, as traditionally done. However, recent studies have shown that working memory performance is higher for meaningful stimuli (i.e., real-world objects) relative to simple features. How does working memory capacity for real-world objects relate to fluid intelligence? To test this, participants (103 young adults) completed different visual working memory tasks that used images of real-world objects or simple colored circles as well as fluid and crystallized intelligence tests. The results showed reliable correlations between all working memory tasks and fluid intelligence scores, and no significant differences between these correlations across stimulus types. Interestingly, fluid intelligence scores were correlated with the difference in working memory performance between real-world objects and colored circles, suggesting that the increase in working memory capacity for meaningful stimuli relates to fluid intelligence abilities. Working memory performance was not reliably correlated with crystallized intelligence in any of the tasks. Collectively, these findings suggest that maintaining real-world objects and colored circles largely rely on shared cognitive processes that may, in part, underlie individual differences in fluid intelligence.