Music shapes the content of spontaneous thought

Spontaneous thought is often considered an unconstrained, internally generated mode of thinking that is independent of the present perceptual environment, making it difficult to study empirically. However, recent accounts have raised the possibility that the generation and content of spontaneous thought can be shaped by even weak perceptual constraints. We leveraged this new perspective to develop a novel approach using music, a ubiquitous stimulus that permeates our everyday environments, as a window into the mechanisms supporting spontaneous thought content. Adults spanning four age groups listened to music from ten different genres and completed the open-ended task of writing descriptions of any thoughts that arose. By applying natural language processing analysis to the spontaneous thought descriptions, we found that thoughts sustained while hearing music from the same genre shared greater semantic similarity than those sustained while hearing music from different genres, and participants from the same age group experienced more similar thoughts than those from different age groups. Properties that varied naturally with genre, including the music’s auditory features, expressed emotions, and contextual associations, all contributed significantly to explaining the greater semantic similarity of thoughts within genres. These results demonstrate that spontaneous thought is jointly shaped by perceptual and experiential constraints, opening new avenues for understanding when and why particular thoughts come to mind, with implications for creativity and mental health.