New research suggests that humans may recognize complexity across different sensory experiences, according to a study published in Nature Human Behaviour. Conducted by Tal Boger and Chaz Firestone of Johns Hopkins University, the study involved 11 experiments aimed at uncovering whether people could identify patterns of complexity across different types of stimuli, such as shapes, sounds, and text. In one of the experiments, participants played a game where they had to choose between two items to earn virtual coins. Some were rewarded for selecting the simpler option, while others were rewarded for choosing the more complex one. After learning the rules through repeated trials, the researchers changed the type of item—such as switching from shapes to sounds. Participants were then asked to apply the same strategy without any additional guidance. Surprisingly, about 72% of the 96 participants followed the learned rule, significantly higher than the 50% expected by chance. The study also found that this recognition of complexity extended beyond shapes and sounds to other categories, such as unfamiliar letter strings, mathematical expressions, and colored dot arrays. In 9 out of 10 pairings tested, participants reliably applied the same complexity rule across different types of stimuli. Even when the task switched from vision to touch—such as feeling 3D-printed outlines and then choosing between visible dot patterns—about 82% of the 99 participants carried the rule over, showing that the concept of complexity could be recognized across different senses. To ensure that participants weren’t just choosing based on obvious features like brightness or size, the researchers designed additional games. They found that the rule did not consistently apply to objects with exaggerated characteristics, reinforcing the idea that complexity, rather than size or color, was the key factor. However, when complexity was presented in confusing or mismatched ways—such as pairing a complex shape with a simple word—participants made more mistakes and responded more slowly, indicating that the connection between complexity and reward was automatic and not necessarily deliberate. Finally, the study explored whether this sense of complexity influenced subjective preferences. In an experiment with 150 participants, people were asked to choose which items they found more or less beautiful, comparing pairs from one category at a time. While there were no rewards or right answers, those who preferred complex shapes also tended to favor complex patterns in melodies, letter strings, and mathematical expressions. Although the preferences weren’t perfectly aligned across categories, they were more consistent than would be expected by chance. This suggests that our perception of complexity across different sensory experiences may be linked by a shared, underlying sense of complexity.