Chapter 10 begins with the author’s discovery that a phrase she had enunciated—“Sometimes behave so strangely”—when presented repeatedly, came to be heard as sung rather than spoken. This illusion is presented as a sound example. It shows that speech can be perceptually transformed into song without altering the sounds in any way, or by adding any musical context, but simply by repeating a phrase several times over. The speech-to-song illusion, as Deutsch named it, has no obvious explanation in terms of current scientific thinking about the neural underpinnings of speech and music. Many researchers believe that speech and music are each analyzed in independent modules, based on their physical characteristics. This view was supported by studies of stroke patients, some of whom lost their power of speech while their musical abilities remained intact, whereas others lost aspects of musical ability while their speech remained normal. In contrast, philosophers and composers throughout the ages have argued that a continuum extends from ordinary speech at one end to song at the other, with emotional and heavily intoned speech in between. Some recent brain-scanning studies have supported the idea that speech and song are subserved by the same circuitry, while others have shown that song involves more brain regions than speech. Evidence for these different views are currently being debated, but the exact explanation for the speech-to-song illusion remains a mystery.

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.

Abstract Repeated exposure to a spoken phrase can give rise to the perception of the speech-to-song illusion (STS), whereby speech gains musical qualities and begins to sound like singing. STS is known to rely on acoustic cues and may depend on an individual’s ability to extract musical qualities (such as melody and rhythm) from speech acoustics. So far, most research has examined listeners of non-tonal languages, with preliminary evidence indicating that tonal-language listeners experience STS differently, if at all. This study investigated STS in Mandarin Chinese listeners who rated song-likeness of Mandarin sentences before and after repetition and completed the Musical Ear Test. Test sentences were designed to promote the acoustic transmission of either melody or rhythm. Results demonstrated a modest STS effect in Mandarin listeners at the group level, which was independent of sentence acoustics. Individual abilities in rhythm perception had no impact on STS while, somewhat surprisingly, weaker melody perception abilities were found to facilitate STS. This suggests that STS in Mandarin Chinese may be linked to a perceptual distortion of pitch. Overall, the findings indicate that STS mechanisms are shaped by linguistic background of listeners and provide new evidence that language experience can influence music perception and cognition.