21 June: Piera Filippi

From emotional arousal to interactive communication: A comparative approach to prosody in language evolution and acquisition

Piera Filippi (Vrije Universiteit Brussel)

Tuesday 21 June 2016, 11:00–12:30
1.17 Dugald Stewart Building

Writing over a century ago, Darwin hypothesized that vocal emotional expression had ancient evolutionary roots, perhaps dating back to some of our earliest terrestrial ancestors. This suggests that fundamental characteristics of vocal emotional expressions are widely shared among terrestrial vertebrates. Recent studies support this possibility, showing that acoustic attributes of aroused vocalizations are shared across many mammalian species, and that humans can use these attributes to infer emotional content. In a recent empirical study, we showed that human participants use specific acoustic correlates (differences in fundamental frequency and spectral center of gravity) to judge the emotional content of vocalizations of nine vertebrate species: hourglass treefrog, American alligator, black-capped chickadee, common raven, domestic pig, giant panda, African elephant, Barbary macaque, and human. These species represent three different biological classes – amphibia, reptilia (non-aves and aves), mammalia – that diverge in size, ecological habitat, and social structure. These results suggest that fundamental mechanisms of vocal emotional expression are widely shared among vertebrates and could represent an ancient signaling system. But what’s the evolutionary link between the ability to interpret emotional arousal across vertebrate species and the ability for human linguistic communication? I suggest to identify this link in the ability to actively modulate emotional sounds within communicative interactions. Specifically, within a comparative approach to sound modulation in human and nonhuman vocal communication systems, I propose a new perspective on the ability for interactional prosody (AIP) which includes the following processes: (i) to actively control and modulate frequency, tempo and amplitude of vocalizations; (ii) to coordinate sound production with one or more individuals; (iii) to express or evoke emotional information. I hypothesize that AIP paved the way for the evolution of language and continues to play a vital role in the acquisition of language. In support of this hypothesis, I review empirical studies on the adaptive value of AIP in nonhuman primates and mammals and on the beneficial effects of AIP in scaffolding verbal language acquisition. I emphasize the key role of the social and interactive aspect of AIP in relation to the evolution and ontogenetic development of language. Finally, I describe recent empirical data on humans, showing that the prosodic modulation of the voice is dominant over verbal content and faces in emotion communication. This finding aligns with the hypothesis that prosody is evolutionarily older than the emergence of segmental articulation, and might have paved the way to its origins.

24 May: Jérôme Michaud

The utterance selection model and the cultural evolution of languages

Jérôme Michaud (Edinburgh)

Tuesday 24 May 2016, 11:00–12:30
1.17 Dugald Stewart Building

In this talk, I discuss the cultural evolution of languages in the light of the utterance selection model (USM) for language change developed in 2006 by Baxter et al.

I start by discussing the process of cultural evolution in general and then recall the USM definition. This is a relatively simple agent-based model simulating the communicative interactions between interconnected agents on a network. Since a language can be defined at the population level, it is important to be able to understand the dynamics of the complete population. I present a stochastic (heterogeneous) mean field approximation of the USM that allows me to discuss the influence of different parameters, such as the connectivity of agents, the rate of production error, the learning rate, the importance of different agents and the size of the population. I show that the global behaviour of the population can be mainly understood in terms of two independent parameters and that there is a critical parameter at which the behaviour of the of the population qualitatively changes.

To complete the discussion, I introduce a modification of this model that includes a mechanism for agents to explicitly develop preferences for particular variants and investigate the consequences of this modification.

17 May: Richard Futrell

Crosslinguistic quantitative syntax: Dependency length minimization and beyond

Richard Futrell (MIT)
Work with Kyle Mahowald and Ted Gibson

Tuesday 17 May 2016, 11:00–12:30
1.17 Dugald Stewart Building

Recently available crosslinguistic dependency corpora, such as those from the Universal Dependencies project, have made it possible to investigate the quantitative syntactic properties of dozens of languages. We use these corpora to test the quantitative predictions of communicative functional explanations for typological universals.

One such prominent theory is dependency length minimization: various psycholinguistic theories have suggested that language is easier to produce and comprehend when distances between words linked in syntactic dependencies are short, and a functional pressure for short dependencies has been advanced as a theory to explain word order universals. In order to investigate this effect at a large scale in dependency corpora, we compare the dependency length of attested sentences to random baseline reorderings of those sentences under a series of linguistically motivated constraints. First, we establish that a dependency length minimization effect exists in over 40 languages by showing that real sentences have shorter dependency lengths than random projective reorderings with fixed and free word order. Next, we address the question of whether the observed minimization is the result of utterance-specific speaker choice (usage) or constraints on possible orders in a language (grammar). To investigate this, we develop probabilistic models to induce linearization grammars from dependency corpora, and compare the attested orders for sentences in the corpora to random grammatical orders for the same sentences under these models. In most languages, attested dependency length is shorter than this baseline as well. Subject to the limitations of the linearization models, this result suggests active dependency length minimization in usage. Finally, we discuss some of the residual variance between languages in dependency length, which cannot be explained by a simple dependency length minimization account. We show that languages have less dependency length minimization when they are head-final, morphologically complex, and/or have high degrees of word order freedom. Explaining these phenomena is a challenge for functional typology.

10 May: Ellen Garland

Cultural transmission of humpback whale song

Ellen Garland (St Andrews)

Tuesday 10 May 2016, 11:00–12:30
1.17 Dugald Stewart Building

Cultural transmission, the social learning of information or behaviors from conspecifics, is believed to occur in a number of groups of animals, including primates, cetaceans, and birds. Cultural traits can be passed vertically (from parents to offspring), obliquely (from the previous generation via a nonparent model to younger individuals), or horizontally (between unrelated individuals from similar age classes or within generations). Male humpback whales (Megaptera novaeangliae) have a highly stereotyped, repetitive, and progressively evolving vocal sexual display or “song” that functions in sexual selection (through mate attraction and/or male social sorting). All males within a population conform to the current version of the display (song type), and similarities may exist among the songs of populations within an ocean basin. Here we present a striking pattern of horizontal transmission: multiple song types spread rapidly and repeatedly in a unidirectional manner, like cultural ripples, eastward through the populations in the western and central South Pacific over an 11-year period. This is the first documentation of a repeated, dynamic cultural change occurring across multiple populations at such a large geographic scale.