Concluding Speculations

This final chapter is speculative. It addresses the entrainment assumptions of universality and resonance by reviewing the natural environments of a range of different species, from crickets to whales. The idea is that sensitivity to both rate and rhythm across different species is support for assuming natural driving rhythms exist that facilitate entrainment in a wide range of other species. Also discussed are two artifactual environments experienced by humans: namely, that of laboratory studies that artificially control stimulus timing and the contemporary machine-driven environment of computers and iPhones. The latter are speculated to lead to a sporadic habitat based on fast irregular (artifactual) driving rhythms.

Learning Speech

This culminating chapter is divided into five parts. Following an initial background are sections related to time spans of phonemes, syllables, words, and phrases, respectively. A historical background, lodged in both linguistics and psychology, presents domain-specific explanations of perceptual learning of speech versus music. In contrast, this chapter continues a domain-general argument by assuming that learning of speech (as well as music) depends on grasping abstract time relationships (attractors) at various time scales in speech as well as in music. This portrait brings together many familiar dynamic attending constructs from earlier chapters. It outlines three stages of phoneme learning in infants. With age, learning develops to include learning of attractor profiles in syllables and words. Ultimately, word learning is shown to rely on both traditional and transient mode-locking.

Learning Time Patterns

This chapter is important in that it lays a foundation for claims throughout this book that entrainment serves a platform for learning. In this chapter, this idea is developed in the context of learning categories of meter (e.g., duple meter vs. triple meter). The key difference is that entrainment depends on coupling parameters supplied by external driving rhythm force, whereas learning depends on a binding parameter which is strengthened simply by repeated synchronous activity of two or more oscillations. Against a backdrop of evidence indicating that musicians especially possess skill in recognizing metric categories, this chapter develops the coupling–binding distinction with the aim of showing that what people learn when exposed to metrical time patterns are global attractors instilled by learning a variety of different instances in a given metric category.

Parallelism

The ability to “keep time” refers to the momentary tracking of a dynamic environmental event; sometimes our natural tendencies for “keeping” time are apparent, while the underlying synchronies of attending may be less obvious. This chapter has three goals. The first is to demonstrate a parallelism between the production of an event (e.g., a spoken phrase or sentence) and one’s expectancy or perception of that event. Expressing such parallels requires specifying underlying factors in production and expectancies, such as the attractors and referent oscillation responsible for producing a tempo curve. The second goal is to propose the respective roles of voluntary and involuntary factors that figure into these expressions. The third goal is to present readers with a sample of studies that embody parallelism.

Speech Timing

Against a historic background which features an early interest in isochrony in speech production or perception, some contemporary approaches to speech timing shifted to feature segmented durations, rather than rhythms, as the basis of speech timing. Recently, another turnabout revived heightening interest in speech rhythms. This is documented with research suggesting that listeners exhibit sensitivities not only to quasi-isochronous speech but also to relative timing reminiscent of metrical relationships. The latter is indicative of the traditional mode-locking entrainment protocol. This chapter traces this evolution. Also introduced are other dynamic attending constructs, such as transient mode-locking, that are proposed to operate while attending to speech timing. Finally, classic descriptions of sequential grouping tendencies (i.e., the Iambic/Trochaic law) are translated into entrainment rules for the formation of temporal groups.

Musical Melodies

This chapter has three major sections. The first section introduces musical scales together with psychological implications. The second section focuses on theory and research surrounding musical tonality. The third section presents issues surrounding the perception of melodic contours. A number of theories are explored, some including Gestalt concepts, as well as concepts based on dynamic attending theory (DAT). The latter theory is shown to address attending to both musical tonality and contour. In general, percepts of tonal melodies lend themselves to DAT interpretations based on attractor profiles, whereas melodic contour perceptions can be explained in terms of exogenous entrainment to a changing frequency.

Tuning in to Slow Events

This chapter addresses entrainments in various slow events. It challenges the idea that only slow events that are isochronous are capable of entraining neural oscillations. It tackles entrainments in events that afford quasi-isochronous driving rhythms as well as in events that are markedly non-isochronous (but coherent). Coherent sequences have time patterns as in short-short-long or long-short-short sequences. This is an important chapter as it differentiates two entrainment protocols: traditional mode-locking versus transient mode-locking. Traditional mode-locking is familiar; it describes entrainment when neither the driving rhythm nor the driven rhythm change significantly (fluctuations are all right). Traditional mode-locking is governed by a single (global) attractor. By contrast, transient mode-locking refers to fleeting entrainments to changing driving rhythms, given the persisting period of driven oscillation. This form of mode-locking delivers a series of (local) attractors. This chapter develops these ideas and provides many examples.

Tuning in to Very Fast Events

This chapter demonstrates that entrainment applies to very fast events, namely sounds with high frequencies. To illustrate this, prominent approaches to pitch perception are sketched along with basic pitch perception phenomena (e.g., virtual pitch perception). In this chapter, multiple frequency components comprise a single complex sound, and people must judge the pitch of this collection of frequencies. Both a successful psychoacoustic theory of pitch perception and a dynamic attending approach offer valid explanations of various phenomena surrounding the pitch of such sounds. This suggests the potential of entrainment in describing pitch perception (i.e., entrainments at fast time scales). The perception of consonance and dissonance is also considered, where dissonance is linked to complex synchronicities termed attractors. Finally, this chapter introduces oscillator clusters, a group of endogenously entrained oscillations.

Melodies of Speech

The focus in this chapter is on fast speech events. Specifically, it centers upon the melodies of speech created by vocal modulations of micro-driving rhythms associated with a speaker’s fundamental frequency. Briefly, it is about vocal intonation patterns in speech. Theoretically, it concentrates on a listener’s ability to engage pitch tracking (i.e., frequency following) to follow a speaker’s changing vocal pitch. To describe pitch tracking, pitch contrasts arising from vocal modulations are formalized using the important entrainment construct of a detuning curve. This methodology is described in detail. A derivative of this curve is the isolation of pitch accents as extreme pitch contrasts. The remainder of this chapter focuses on the role of pitch accents in outlining slower macro-rhythms of intonation that invite either traditional mode-locking (hence global attractors) or transient mode-locking (hence attractor profiles).

The Temporal Niche

Members of the same species share categorically similar rhythmic events in their communicative activities. In this fashion, conspecifics are bound in time. And this dependence on time during communicative interactions is at the heart of dynamic attending. The chapter develops the hypothesis that the resonance and entrainment capacities of an individual change over a life span. Resonance between driving rhythm and its neural correlate predicts slowing of driven oscillator periods over the life span. A corollary holds that entrainment predicts optimal phase-coupling of the driven (oscillator) with the driving (event) rhythm over the life span. Together, these two trends form the aging hypothesis. Evidence supporting the aging hypothesis is reviewed in this chapter.