The word entrainment originates in the mid 16th century, meaning ‘bring on as a consequence’ (OED), from French entrainer, en (in) + trainer (to drag). When applied to biology, it means that the biology ‘of a rhythm or something which varies rhythmically’ causing ‘another to gradually fall into synchronization with it’.
In the model of entrainment formed in ethnomusicology (Clayton, Sager and Will 2005), rhythmic processes endogenous to the listener entrain to cues in the musical sound (Large and Kolen 1994). Research into interpersonal interaction extends this entrainment model, e.g. the aforementioned studies of motherese and the evolution of musical behaviour in the human species (Merker 2000). Clayton et al. (Op. cit.) define entrainment as a process whereby two rhythmic processes interact with each other in such a way that they adjust towards and eventually ‘lock in’ to a common phase and/or periodicity (p. 3).
Research into music in cognition (Jones 1976; Jones and Boltz 1989; McCauley et al. 2006; Himberg 2006) has shown that the ways in which musical time tends to unfold predictably helps optimize the ways in which participants deploy their attentional resources in making sense of the music. Large and Jones (1999) developed a theory of attentional dynamics to explain how listeners respond to systematic change in everyday events whilst retaining a general sense of their rhythmic structure. The approach describes attending as the behaviour of internal oscillations, called attending rhythms, that are capable of entraining to external events and targeting attentional energy to expected points in time.
Entrainment has been of particular interest to music researchers as it provides a framework for explaining and measuring how we temporally perceive music and how we are able to move in time together with music. ‘What is unique and in a sense a diagnostic for music in the time domain, is its capacity to serve as a vehicle for the temporal synchronization of identical or different behavioural patterns, to extraordinary levels of temporal precision.’… ‘behavioural timing unique to music—the even subdivision of time by the musical pulse, also called beat or tactus ‘(Arom 1991)’.
In his study of beat entrainment, Himberg (2011) found that when two people are tapping to a metronome (the artificial beat), their tapping drifts from the metronome as they tap to the beat of each other. After some time, their tapping realigns with the metronome and then it drifts off again to each others’ beat. All this happens with no awareness on the part of the ‘tappers’ who think they have been tapping to the metronome (the artificial beat) all along. Himberg’s study compares tapping in human dyads and non-responsive computer partners and finds that interpersonal entrainment, with mutual adaptation, produces a tighter connection than tapping to a computer partner. His research reveals that we can discern the difference between a computer-generated beat. His experiment on tappers entraining to each other shows how in our everyday mutual synchronization and entrainment behaviours our attending rhythms come to entrain each other.