Where does synchrony collide?

In 1665 Christiaan Huygens, confined to bed and watching two pendulum clocks hung from the same wooden beam, noticed that their swings always settled into opposite step and stayed locked there, an effect he traced to faint vibrations passing through the shared support. Kuramoto's 1975 Self-entrainment of a population of coupled non-linear oscillators gave the modern mathematical account, showing how a large population of oscillators with different natural rhythms can spontaneously fall into a common rhythm once the coupling between them is strong enough. Here the referent is the physical locking of rhythms among interacting oscillators, from clocks to fireflies to power grids, and it has nothing in common with a coordinated exchange between a parent and infant, a crowd moving as one in a rite, or a language described at a single point in time.[1][2]

Unit

One pair or population of oscillators sharing a common frequency and a fixed phase relation

Recovery means

Not applicable

Measured by

Quantified by the phase difference between oscillators and by an order parameter that runs from zero when rhythms are scattered to one when they are fully locked

Émile Durkheim's 1912 Les formes élémentaires de la vie religieuse described how people gathered in a rite, moving, chanting, and gesturing together, generate a shared emotional charge he called collective effervescence, which binds the group and renews their common bonds. Konvalinka and colleagues' 2011 study of a fire-walking ritual measured the effect directly, recording heart rhythms that rose and fell in step between the performers and the relatives watching them. The referent is the moment-to-moment matching of bodies and feeling across many people in a shared rite, and it is distinct from two clocks falling into step, a single caregiver and baby trading signals, or a snapshot of a language at one time.[3][4]

Unit

One gathering of people whose movements and arousal rise and fall together during a rite

Recovery means

Not applicable

Measured by

Assessed by observation of coordinated movement and, in recent work, by physiological signals such as synchronized heart rate across participants

Ferdinand de Saussure's Cours de linguistique générale, published in 1916 from his lecture notes, drew a sharp line between two ways of studying a language: synchrony, the description of a language as a working system at one moment, and diachrony, the study of how it changes across time. For Saussure the synchronic view treats the language as a network of relations that speakers actually use, held still at a single date, without regard to its history. The referent is a state of a language captured at one point in time, a matter of method in the study of words, and it bears no relation to clocks locking step, hearts beating together in a rite, or a caregiver and infant coordinating their exchanges.[5]

Unit

One description of a language treated as a complete system at a single point in time

Recovery means

Not applicable

Measured by

Established by analysing the relations among a language's elements as they stand at one date, set apart from their historical development

Condon and Sander's 1974 Neonate movement is synchronized with adult speech reported that newborns, within their first day, move their bodies in fine time with the rhythm of adult talk directed at them, evidence of coordination between caregiver and child from the very start. Feldman's 2007 review Parent-infant synchrony and the construction of shared timing drew the many later findings together, describing how a parent and infant match the timing of gaze, touch, voice, and even heart rhythm in their back-and-forth exchanges, and linking that matching to later development. The referent is the moment-by-moment coordination within a single caregiver and infant pair, and it is a different thing from oscillators locking frequency, a crowd unified in ritual, or a language held still for description.[6][7]

Unit

One caregiver and infant pair whose behaviours align in timing during interaction

Recovery means

Not applicable

Measured by

Coded from video of face-to-face interaction by the timing overlap of gaze, affect, touch, and voice, and increasingly by matched physiological signals