On the distinction between involuntary musical imagery, musical hallucinosis, and musical hallucinations

This article seeks to combine medical reports on musical hallucinations with more recent insights into the everyday occurrence of "earworms" or involuntary musical imagery, which has become the equivalent and widely accepted academic notion for this phenomenon. Despite the fact that the casual term was originally derived from the German word Ohrwurm, one of the earliest references to this phenomenon draws on the notion of hallucinations. In a footnote to the interpretation of dreams, Freud (1900/ 1978) mentions a female client who "involuntarily, and against her will, hears-i.e. hallucinates-songs or fragments of them" (p. 418). In addition, Freud points out that this person is "certainly not paranoic" (p. 419), so there is no reason to assume medical disorders. Freud, however, was in favor of the term hallucination (which was commonly used to describe symptoms of schizophrenia), because these led to the development of psychoanalysis in the first place.In our time, hallucinations are usually associated with pathological conditions (besides occurrences as a religious, psychedelic, etc. phenomenon), whereas involuntary musical imagery is an accepted everyday phenomenon. It seems to occur in an otherwise healthy, vast majority of the population (Liikkanen, 2008). The main distinction between hallucinations and involuntary musical imagery (INMI) can be described by how real the music seems to be. Hallucinations occur as if they were real, as if the music were playing somewhere (some individuals realize the nonexistence of the sound source; others do not), whereas INMI is not a real perception-that is, the music seems to be a shadow or an image of a musical piece heard before. People experiencing INMI are consistently aware that the music is only playing in their heads. Meanwhile, available research displays a fine-grained spectrum of phenomena on the continuum between involuntary musical imagery on one end and clinical hallucinations on the other. We now introduce these distinctions and the according terminology by discussing four typical occurrences.Involuntary Musical Imagery or the Everyday EarwormThe term involuntary musical imagery was first used by Sacks (2007, p. 33) to describe the mental capacity of "filling in" music when the volume is turned down or gaps are inserted. The term is thus not related to medical disorders. Later, Liikkanen (2008) introduced the abbreviation INMI and defined the phenomenon as follows: "imagined musical experiences that originate without the subjects' intention and are not pathological" (Liikkanen, 2012a, p. 218). In a survey with German natives on the everyday occurrence of earworms (Hemming, 2009),1 the term involuntary musical imagery was not yet taken up but exactly matches the focus of the study: primary data source was 59 guided interviews with participants who had listened to a CD with 20 potentially "catchy" tunes for several weeks. As is common in research on musical preferences, the 20 titles on the CD covered 20 different genres, including popular, jazz, and classical, as well as vocal and instrumental music. Participants were asked to provide ratings for the respective genres as well as for the specific titles on a supplementary questionnaire. In addition, their amount of musical training and activity were investigated. Many of the results displayed a one-third to two-thirds relationship: INMI occurred with preferred titles/genres in about two thirds of the cases and in about one third with disliked titles/genres. Once established, INMI was considered pleasant in two thirds of the cases and unpleasant in one third of the cases. Some people reported the start of INMI while the stimulus was still playing; in other cases, INMI occurred with a delay of up to several weeks. INMI may persist from several minutes to several weeks; 2.5 weeks was the maximum found. Quite often, INMI starts in periods of mental relaxation, sometimes paired with physical activity. There was no (significant) difference in the number of INMIs between people inactive or active in music. …