What is consciousness? Can we study consciousness scientifically or is consciousness beyond empirical science, as many philosophers have claimed throughout the ages? This chapter provides a short history of the topic, including philosophical and scientific milestones, and gives an overview of what is to come in subsequent chapters.

Many studies in the linguistic literature have tried to explain the rhythmic component of speech by resorting to the notion of isochrony. The problems with such approaches have been demonstrated in various recent works, owing to the fact that natural speech is highly irregular and quasi-periodic at best. Rhythm also plays a role in the link between brain oscillations and linguistic constituents, where entrainment is often assumed to be the underlying mechanism. Here too, the non-isochronous nature of the speech signal led recent works to call for a more nuanced understanding of entrainment in the context of language. We suggest that rhythm is the timescale within which temporal relationships between isolated events are perceived (about 0.5–12 Hz). We claim that while music tends to use this timescale to promote phase-locking to an external clock, language exploits it to achieve an effective distinction between fast and slow rates in prosody.

The temporal signatures that characterize speech – especially its prosodic qualities – are observable in the movements of the hands and bodies of its speakers. A neurobiological account of these prosodic rhythms is thus likely to benefit from insights on the neural coding principles underlying co-speech gestures. Here we consider whether the vestibular system, a sensory system that encodes movements of the body, contributes to prosodic processing. Careful review of the vestibular system’s anatomy and physiology, its role in dynamic attention and active inference, its relevance for the perception and production of rhythmic sound sequences, and its involvement in vocalization all point to a potential role for vestibular codes in the neural tracking of speech. Noting that the kinematics and time course of co-speech movements closely mirror prosodic fluctuations in spoken language, we propose that the vestibular system cooperates with other afferent networks to encode and decode prosodic features in multimodal discourse and possibly in the processing of speech presented unimodally.

The developmental community is beginning to embrace the idea of exaggerated rhythm in infant- and child-directed speech providing critical information during early language acquisition. Here, we consider I/CDS as a special case of language, with enhanced multimodal temporal and prosodic cues, attuned to the needs of the listener. The evidence supporting this idea is largely based on language disorders (e.g., dyslexia, DLD), with relatively sparse extant literature on typical language development. However, the field is rapidly growing, with methodological advances in cortical and behavioral rhythmic tracking allowing us to better understand the organizing principles of speech and language processing. We address the multiple approaches adopted across research communities, providing a commentary on both the reach and suitability of these methods. From a nascent literature, the chapter aims to paint a coherent picture of the field’s current state, providing recommendations for future research.

Intonation units (IUs) are a fundamental prosodic unit of all known human languages, and as such they likely constitute an absolute universal property of language. IUs are chunks defined by a specific pattern of syllable delivery, together with resets in pitch and articulatory force. In this chapter we discuss IUs from four different perspectives and introduce them within the context of rhythms of speech, language, and the brain. First, we provide a detailed description of how IUs are defined. Second, we review linguistic research on the roles of IUs in communication, including their cross-linguistic applicability. This body of research suggests that IUs provide a universal structural cue for the cognitive dynamics of speech production and comprehension at a timescale of ~1 Hz. Third, we synthesize the linguistic perspective with findings from the study of brain rhythms and cognition. Finally, we review the existing algorithmic tools for IU identification from speech acoustics, to facilitate the incorporation of IUs in experimental and quantitative research.

The temporal structure of speech provides crucial information to listeners for comprehension: In particular, the slow modulations in the amplitude envelope constitute important landmarks to discretize the continuous signal into linguistic units. Contemporary models of speech perception attribute a major functional role to brain rhythmic activity in this process: By aligning their phase to the quasi-periodic patterns in speech, neural oscillations would facilitate speech decoding. We here review evidence from EEG/MEG studies showing neural theta-range (~4–8 Hz) tracking of syllabic rhythm, with a special interest in speech rate variations. We also discuss to what extent neural oscillatory coupling contributes to, and is in turn modulated by, speech intelligibility, namely whether it is only acoustically or also linguistically guided. We finally review some findings showing that in addition to auditory cortex, motor regions play an active role in the oscillatory dynamic underlying speech processing.

The prosody of spoken language is characterized by quasi-rhythmic features, which are perceivable by the fetus already from the third trimester of gestation. Recent research studying infant cognition is increasingly focusing on oscillations as a reliable measure of brain responses to quasi-rhythmic auditory stimuli, such as speech at different levels of granularity. There is indeed increasing evidence for a match between the frequency of neural oscillations and the rates of different linguistic units, such as phonemes, syllables, and phrases, both in adults and children. Here we review recent advances in how neural activity aligns with language input at different levels of language structure and organization, at different developmental stages in the first year of life. Importantly, we discuss how this neural architecture may support the development of grammar.

Why do so many people believe the 2020 U.S. election was rigged or that vaccines might cause autism, despite a lack of credible evidence? Chapter 3 explores this question through four key concepts: (1) psychological needs and goals, (2) cognitive heuristics and biases, (3) motivated reasoning, and (4) the viral spread of memes and misinformation. I argue that these false beliefs persist because they satisfy deep psychological needs—for identity, meaning, control, status, or affiliation. The beliefs obtained credibility through social referencing and conformity to ingroup opinions, as well as from constant repetition. Cognitive biases—including availability, stereotyping, confirmation bias, and myside bias—further entrench these views. Another cause of the problem was the sharing of memes and conspiracy theories over the Internet, which reinforces a sense of affiliation and indirect control.¶ Together with identity politics, the selective exposure to information, and weakened trust in epistemic institutions, these forces have accelerated political polarization, endangered public health, and contributed to the “pollution” of the epistemic environment.

Recent studies have shown that neural activity tracks the syntactic structure of phrases and sentences in connected speech. This work has sparked intense debate, with some researchers aiming to account for the effect in terms of the overt or imposed prosodic properties of the speech signal. In this chapter, we present four types of arguments against attempts to explain putatively syntactic tracking effects in prosodic terms. The most important limitation of such prosodic accounts is that they are architecturally incomplete, as prosodic information does not arise in speech autonomously. Prosodic and syntactic structure are interrelated, so prosodic cues are informative about the intended syntactic analysis, and syntactic information can be used to aid speech perception. Rather than trying to attribute neural tracking effects exclusively to one linguistic component, we consider it more fruitful to think about ways in which the interaction between the components drives the neural signal.

One of the riddles of human communication is interlocutors’ ability to adapt to “noisy” inputs. It is argued that it is the interpersonal coordination of rhythmic structure underlying this ability, which can be selectively activated. This process is described as a set of mechanisms operating on linguistic and phonetic structures: Interaction Phonology. Interaction phonology provides the necessary scaffold for enabling an alignment of phonetic-phonological and potentially also higher-order linguistic representations. This coordination process relies on the rhythmic structure of the individual language or register pertaining to the ongoing communication. That way, interlocutors can attend to relevant phonetic detail unveiling higher-order symbolic information and adapt their own rhythmic pattern to enhance mutual comprehension. The testable predictions of Interaction Phonology are discussed in the light of recent empirical evidence, and the initial version of Interaction Phonology is modified: Perception–production coupling is marked as optional, and the automaticity between rhythmic entrainment and higher-order symbolic alignment is questioned.

Temporal properties, such as duration, rate, and rhythm, are crucial aspects influencing the perception and production of speech. To study how these properties affect speech processing, researchers can create retimed experimental stimuli with varying temporal patterns. However, retiming speech also poses significant challenges, such as preserving naturalness, intelligibility, and prosody. In this chapter, we present three methods of altering the acoustic speech signal to achieve a desired rhythmic structure. Each method differs in how it adjusts the timing of the utterance and its segments. The methods are used to create stimuli with regular isochronous stress. We evaluate the methods in terms of how much they disrupt the speech signal and how effective they are in achieving isochrony. Finally, we demonstrate how retiming can be used to produce stimuli with more naturalistic rhythmic characteristics. We show that retiming can be a powerful tool for exploring perceptual effects of timing in speech.

Despite their genetic relatedness, Romance languages and dialects exhibit considerable differences in their phonological systems. In rhythm typology, Spanish was long considered a textbook example of the so-called syllable-timing type, while the classifications for French and Portuguese were often disputed. Rhythmic differences were also found between the more accent-based European varieties of Portuguese and the more syllable-based Brazilian dialects. Our contribution first endeavors to carry out a phonological assessment of the degree of syllable prominence and accent prominence in European French, Spanish, and Portuguese, as well as in varieties of Spanish and Portuguese spoken in the Americas. In a second step, we conduct a phonetic case study using comparable spoken language data of the varieties under investigation.

Chapters Four through Nine portray the most well-known theories of consciousness. Each portrayal was written by an eminent proponent of that particular theory, and thus the portrayals provide accurate and unbiased information. Chapter Four introduces the topic, provides the tools for analyzing the theories logically, and shows that a theory needs to jointly address conscious and non-conscious brain activity which, as it turns out, many theories do not do. The chapter features the learning and consciousness theory (SOMA).

We provide an in-depth analysis of the theories portrayed in the previous chapters. As it turns out, all theories except illusionist theories are monofactorial theories, proposing that one thing is crucial for consciousness, such as a workspace. The monofactorial nature of such theories is the main reason why the theories face the challenges that we outlined. A further consequence is that consciousness is epiphenomenal according to these theories, i.e. consciousness has no impact on actions, feelings, or anything physical. Epiphenomenalism is hard to reconcile with empirical science. We argue that these problems are avoided by a multifactorial framework, in which consciousness is treated as a supra-ordinate term picking out a specific constellation of interacting mechanisms. On this view, progress hinges on identifying the computational or biological problem(s) that this constellation solves.

Spoken language is a complex signal that evolves over time and conveys rhythm across multiple timescales. Beyond the signal level, there is rhythm in social aspects of speech communication such as joint attention, gestures, or turn-taking. Neural oscillations have in many cases been shown to directly reflect the rhythmic features of speech. However, the knowledge about origins, specific functions, and potential interactions of different rhythms and their neural signatures is far from complete. An integrative perspective that builds on phylogenetic and ontogenetic developments can provide some of the missing components. Here we propose that speech production and perception engage evolutionary ancient temporal processing mechanisms that guide sensorimotor sequencing and the allocation of cognitive resources in time. Slow-wave (delta-to-theta band) oscillations are the designated common denominator of these mechanisms, which interact in a speech-specific variant of the perception–action cycle with the goal to achieve optimal temporal coordination and predictive adaptation in speech communication.