Abstract
Involuntary musical imagery (INMI) refers to a conscious mental experience of music that occurs without deliberate efforts to initiate or sustain it. This experience often consists of the repetition of a short fragment of a melody, colloquially called an "earworm." Here, we present the first comprehensive, qualitative review of published empirical research on INMI to date. We performed an extensive literature search and discovered, in total, 47 studies from 33 peer-reviewed articles that met the inclusion criteria for the review. In analyzing the content of these studies, we identified four major research themes, which concern the phenomenology, dynamics, individual differences, and musical features of INMI. The findings answer many questions of scientific interest-for instance, what is typical in terms of INMI frequency, duration, and content; which factors influence INMI onset; and whether demographic and personality factors can explain individual differences in susceptibility and responses to INMI. This review showcases INMI as a well-established phenomenon in light of a substantial body of empirical studies that have accumulated consistent results. Although the populations under study show an unfavorable bias towards Western, educated participants, the evidence depicts INMI as a universal psychological phenomenon, the possible function of which we do not yet fully understand. The concluding section introduces several suggestions for future research to expand on the topic.