Musical rhythm and affect: Comment on "The quartet theory of human emotions: An integrative and neurofunctional model" by S. Koelsch et al.

The Quartet Theory of Human Emotion (QT) proposed by Koelsch et al. [1] adds to existing affective models, e.g. by directing more attention to emotional contagion, attachment-related and non-goal-directed emotions. Such an approach seems particularly appropriate to modelling musical emotions, and music is indeed a recurring example in the text, used to illustrate the distinct characteristics of the affect systems that are at the centre of the theory. Yet, it would seem important for any theory of emotion to account for basic functions such as prediction and anticipation, which are only briefly mentioned. Here we propose that QT, specifically its focus on emotional contagion, attachmentrelated and non-goal directed emotions, might help generate new ideas about a largely neglected source of emotion – rhythm – a musical property that relies fundamentally on the mechanism of prediction. Musical rhythm is usually defined as patterns of discrete durations which are usually (but not always) perceived in relation to a pulse, i.e. an underlying framework of regularly occurring beats, also called metre. It is the online prediction of this pulse that enables the synchronisation of body-movements in dance, a musical activity that is uniquely human, enjoyed across history and a wide range of cultures. Entrainment – the process by which an oscillating process is coupled and synchronised with another oscillating process – is believed to provide the mechanism for such sensorimotor synchronisation [2]. Perceptual and motor entrainment relies heavily on temporal expectation and prediction in order for successful coupling to occur, and recently researchers have begun to address its affective significance. One hypothesis claims that through shared sense of time, rhythmic entrainment enables the transfer of emotions between music listeners, dancers and performers [3]. In QT, Koelsch et al. mention that such emotional contagion is afforded by music as well as affective prosody, which provide more direct translations of emotion than semantic language. We would like to emphasise that it is the rhythmic aspects and the associated entrainment in music (and likely also affective prosody) that provides the mechanism for such transfers of emotion. Although there is not yet evidence on the neural basis of entrainment-related emotional contagion, some researchers have suggested that the mirror neuron system and the insula could be involved [4].