A phrase in a loop: A rethink of verbatim repetition in the speech-to-song illusion and a new approach to the study of involuntary auditory imagery

The human mind engages with repetition both in the form of external stimulation and as an internal psychological phenomenon. I studied these two facets of repetition in 111 musically untrained participants. The investigation was in two parts. In the first part, I looked at the speech-to-song (STS) illusion by comparing ratings of musicality for identical looped (repeated) spoken phrases and for looped spoken phrases including pitch transpositions. Contrary to previous evidence, the stimuli containing transposed presentations were rated more song-like. I attribute this finding to the particular patterns of transpositions used and the fact that the interval of transposition was a major second as opposed to the fractions of semitones used in previous studies. In the second part of the investigation, I partially adopted the stimulus design of the STS illusion paradigm, presenting participants with looped phrases and single phrases. Participants were asked to suppress them and click a button if they thought of them. An increase in button clicks suggests that participants found it significantly harder to suppress the looped phrases than the single phrases. As the stimuli in the second part had been shown in previous research not to induce the STS illusion when repeated, I attribute the differences between participants’ responses to the two kinds of stimuli to the repetition of the phrases rather than their being perceived as song-like. I consider these findings in the light of research on earworms, or involuntary musical imagery. Future directions for a more in-depth exploration of the STS illusion in conjunction with auditory imagery are also briefly discussed.