Psychometric evaluation of the Involuntary Musical Imagery Scale (IMIS) in a South African sample

Involuntary musical imagery (INMI) is a common variety of musical imagery (MI) that has been a key research interest in the psychology of music over the last ten years. The Involuntary Musical Imagery Scale (IMIS), a closed-ended self-report instrument that offers a standardized means of assessing different aspects of earworm experience, has previously been evaluated psychometrically in at least two predominantly Euro-American samples. This report extends the study of INMI, and of the IMIS in particular, into a multicultural and multilingual African context. Responses to the IMIS from a South African student sample were subjected to factor analysis, reliability analysis, and a series of correlational analyses in order to assess its robustness and suitability for cross-cultural research. Results suggest the IMIS has a robust factor structure, reliability characteristics, and internal intercorrelation patterns when compared to previous findings, even outside a Global North setting. Item and subscale scores generally converged with other indicators of MI and INMI frequency, as well as INMI pleasantness and levels of disturbance. In contrast to the findings of much previous research, IMIS Negative Valence correlated negatively with earworm frequency, section length, and episode length, providing support for the claim that earworms are generally a positive rather than aversive experience. Although IMIS earworm frequency was strongly and positively correlated with INMI frequency, they shared only 36.8% variance – a result consistent with concerns that MI/INMI definitions have considerable impact on self-reports of these phenomena, and specifically that the earworm experience should not be equated with or considered prototypical of INMI experience.