4 July: James Winters & Thomas Müller

Asynchronous information transfer as a constraint on the emergence of graphic codes

James Winters & Thomas Müller (MPI Jena)

Tuesday 4 July 2017, 11:00–12:30
1.17 Dugald Stewart Building

Humans commit information to graphic symbols for three basic reasons: as a memory aid, as a recording device, and as a means of communication. Yet, despite the benefits afforded by transmitting information graphically, writing stands out as a unique and compelling mystery: it emerged relatively late in human evolution, and it is the only graphic code which matches the power, precision, and versatility of signed and spoken languages. We argue in this talk that the difficulty of arriving at a graphic code like writing is because asynchronous communication imposes hard constraints on information transfer: access to shared contextual information is circumscribed and recourse to conversational repair mechanisms is removed. To investigate this claim, we present two referential communication experiments. The first experiment shows that graphic codes only reach a stable, accurate and optimal state when used for synchronous communication. By contrast, codes fail to emerge for asynchronous communication, with the systems becoming stuck in a unstable, inaccurate, and sub-optimal configuration.The second experiment singles out the aspect of shared perceptual context from the general characteristics of synchronous communication, and demonstrates its importance for accurate graphic codes. Taken together, these results suggest that the paucity and late-arrival of stable, powerful, and accurate graphic codes in human history is (partly) due to strong constraints on information transfer.

27 June: Cathleen O’Grady

The dot perspective task revisited: Do we automatically process what other people see?

Cathleen O’Grady (Edinburgh)

Tuesday 27 June 2017, 11:00–12:30
1.17 Dugald Stewart Building

The ability to reason about other individuals’ mental states (“mindreading”) is thought to be a central component of social cognition in humans, and particularly essential for language. In order for mindreading to be useful in social interaction, it seems necessary that it is also highly efficient. Samson et al.’s (2010) dot perspective task (DPT) provides evidence that taking another individual’s visual perspective (a very simple form of mindreading) is both rapid and involuntary.

However, variants of the DPT suggest that the task’s headline effect is due not to perspective-taking, but rather to simpler processes that do not entail mindreading. In this talk, I will discuss these competing explanations, and present a new variant of the task that replicates the central finding of the DPT, but suggests that involuntary perspective-taking is not the best explanation for this effect. I will argue that the non-mentalistic account of the DPT may still be useful for understanding the apparent role of mindreading in communication.

13 June: Myrte Vos

Word order, naturalness and conventionalisation: Evidence from silent gesture

Myrte Vos (University of Amsterdam)

Tuesday 13 June 2017, 11:00–12:30
1.17 Dugald Stewart Building

Of the six possible ways to order Subject, Object and Verb, two – SOV and SVO – account for the constituent word order in nearly 80% of the world’s languages. Why? The pragmatic principle ‘Agent first’ accounts for the dominance of S-initial word orders; and recent work in word order typology, creoles, emerging sign languages, and improvised silent gesture suggests that SOV is the natural ‘default’ in nonverbal event representation and early language structure. But if that is so, why is SVO word order nearly as prominent as SOV?

One improvised silent gesture study, from Schouwstra & de Swart (2014), suggests that in improvised communication, the usage of SOV versus SVO is conditioned on the semantic content of the verb. Another study, by Marno, Langus and Nespor (2015) posits that SVO is preferred by the syntax-governing ‘computational system’ of cognition, and that while improvised communication favours SOV, access to a lexicon frees up the cognitive resources needed to employ syntax, and “consequently SVO, the more efficient word order to express syntactic relations, emerges.” In their improvised silent gesture task, wherein half the participants had to improvise their gesturing of simple transitive events and the other half were first taught a gesture lexicon before being asked to communicate, participants trained on a lexicon did indeed favour SVO. We replicated this experiment with stimuli restricted to event-types found to elicit SOV, as well as running an adapted condition using a lexicon of randomly assigned, arbitrary gestures, to further investigate Marno et al.’s hypothesis.

23 May: Sean Roberts

Language adapts to interaction

Sean Roberts (Bristol)

Tuesday 23 May 2017, 11:00–12:30
1.17 Dugald Stewart Building

Language appears to be adapted to constraints from many domains such as production, transmission, memory, processing and acquisition. These adaptations and constraints have formed the basis for theories of language evolution, but arguably the primary ecology of language is face-to-face conversation. Taking turns at talk, repairing problems in communication and organising conversation into contingent sequences seem completely natural to us, but are in fact highly organised, tightly integrated systems which are not shared by any other species.

In this talk I discuss how one might link features of real time interaction to different levels of language evolution: the evolution of a capacity for language; the initial emergence of linguistic systems; and the ongoing cultural evolution of languages. I will illustrate the links in each level using computational models, lab experiments and corpus analyses. I argue that a full explanation of the origin and structures of languages needs to take into account the ecology in which language is used: face to face interactive communication.

9 May: Kenny Smith

Acquiring variation in artificial languages

Kenny Smith (Edinburgh)

Tuesday 9 May 2017, 11:00–12:30
1.17 Dugald Stewart Building

I will present 4 experiments using artificial language learning paradigms to study the ability of adults and children to acquire conditioned and unconditioned variation, in particular looking at their ability and predisposition to condition variation on social and semantic cues.

2 May: Olga Fehér

The effect of semantic cues on the regularisation of unpredictable variation

Olga Fehér (Edinburgh)

Tuesday 2 May 2017, 11:00–12:30
1.17 Dugald Stewart Building

Variation in natural language is constrained: languages tend to lose competing variants over time, and where variation persists its use is conditioned on linguistic or sociolinguistic context. When learners acquire languages that exhibit unpredictable variation (unnatural, unconditioned probabilistic variation), they often eliminate the variation by regularising to one of the competing variants or conditioning on context. We previously found that, in addition to individual learning and transmission, interaction can lead to regularisation through convergence and priming between interlocutors. In this experiment, we investigated the influence of semantic cues on regularisation and conditioning during interaction and transmission. We had adult participants learn and communicate with artificial languages which exhibited unconditioned variation in plural marking. The languages described images that belonged to one or two semantic categories. We found that interacting Dyads regularised in the one category condition by eliminating one of the markers. However, in the two category condition, Dyads maintained variation but without conditioning it on semantic categories. Semantic conditioning occurred only in Singles, gradually during episodes of transmission. The lack of conditioning in Dyads was probably due to strong priming between communicating partners that was present within and across semantic categories. This suggests that the pattern of restricted, conditioned variation in natural language reflects the combined influences of biases in learning, recall and interaction.

25 April: Rebecca Morley

Representational considerations in models of sound change

Rebecca Morley (Ohio State)

Tuesday 25 April 2017, 11:00–12:30
1.17 Dugald Stewart Building

One view of phoneme split takes it to be the result of divergent phonetic variants (e.g., Janda and Joseph 2003). Closely tied to this view is the hypothesis of iterativity: socially motivated phonetic exaggeration accumulating over successive generations (e.g., Labov 1972, Guy 1980), or progressive reduction of frequent words over time (Phillips 1984, Bybee 2002). Iterativity is often assumed to be an inherent property of exemplar models. In a typical scenario production starts with the selection of a token from the desired category. The token is then reduced, lenited, or otherwise altered in some way, resulting in a new phonetic token. The new token is added back to the cloud of stored tokens, and the process starts over again (see Pierrehumbert (2001)). Via this production-perception loop words can be reduced two or more times with respect to the originating token. As more frequent words are more often produced, the chances of multiply reduced tokens are higher. However, contrary to expectation, the mechanism described does not consistently result in shorter word lengths for high-frequency vs. low-frequency words. If frequency of occurrence is expressed in number of tokens, and sampling for production is random, then producing a less reduced token is also more likely in high, than low, frequency categories. And regardless of whether tokens decay, or are replaced, the low-frequency category will eventually ‘catch up’ with the higher-frequency category, and all words will achieve some optimal length. In fact, the production side of this model makes even more problematic predictions. If phoneme-level tokens are selected at random from a phonetically detailed exemplar cloud then egregious mismatch is possible; e.g., an [æ] originally followed by an [m] being selected for a pre-[b] context. It is the same at the word level: a word token originally produced in a frequent collocation, selected for a low-frequency context, etc. Indexing exemplar clouds with all the necessary contextual information, however, results in an explosion of categories, and a depletion of category members. In the limit, each category would contain a single member.

Developing a model for the interaction of synchronic variation and diachronic change requires resolving these and other representational issues, some of which only surface when the entire trajectory of change is considered. Thus, while existing models can capture category shift and merger (Pierrehumbert 2001), or contrast stability and dispersion (Garrett and Johnson 2013, Wedel 2004), there are few that can capture both. The model of Sóskuthy (2013) can generate phoneme split, no-change, and no-split with phonetic shift, as the result of vowel lengthening before voiced obstruents. However, these outcomes require a representational structure in which vowel categories contain at least two sub-categories: pre voiced-obstruent, and pre voiceless-obstruent. Crucially, these subcategories are semi-permeable, and greater frequency of occurrence can cause one sub-category to subsume the other. This scenario raises another unresolved question in exemplar modeling: the interaction between higher and lower level categories. Most models work exclusively at one level, and assume the others. But the process by which the necessary categories at the sub-word level are generated from the word level (or vice versa) is non-trivial, and may not be consistent with model assumptions. A category as abstract as “vowels occurring in environments followed by a voiced obstruent” requires a massive amount of generalization over words with different syllable structures, over obstruents at different places of articulation, etc. And if speakers create categories such as this, then they can be expected to create categories such as “vowels before coronals”, etc. It is not at all clear that existing models will be able to ‘scale up’ adequately under this added complexity.

This work gives a formal account of the representational commitments and assumptions of a range of models, and an assessment of their self-consistency. The claim is that the resolution of outstanding problems lies in determining the division between representations and processes. I argue, on the one hand, that phonetic effects such as “vowel lengthening”, or “vowel nasalization” are not processes themselves, but reside at the representational level. On the other hand, speaking rate must be able to apply after exemplar selection to compress or expand tokens as necessary to match speed of production. I consider prosodic effects, such as phrase-final lengthening to be necessarily processual as well. The ramifications of these representational choices are discussed with respect to the necessary constraints on a model deriving categorical sound change from existing synchronic variation.

18 April: Marieke Schouwstra, Simon Kirby & Jenny Culbertson

Word order universals reflect cognitive biases: Evidence from silent gesture and corpus statistics

Marieke Schouwstra, Simon Kirby, & Jenny Culbertson (Edinburgh)

Tuesday 18 April 2017, 11:00–12:30
1.17 Dugald Stewart Building

We investigate a hypothesized cognitive bias for isomorphic mappings between conceptual structure and linear order in the noun phrase. This bias has been proposed as a possible explanation for a striking asymmetry in the typology of the noun phrase – linear orders which place the adjective closest to the noun, then the numeral, then the demonstrative, are over-represented in the world’s languages.

Previous experimental work has provided evidence that an isomorphism bias affects English-speaking learners’ inferences about the relative order of modifiers in an artificial language. Here, we use the silent gesture paradigm to explore whether the isomorphism bias influences spontaneous gestures innovated by participants in a modality with which they have relatively little prior experience. We find that gesture order largely conforms to the same striking pattern found in noun phrase typology, supporting the role of the isomorphism bias in shaping the emergence of language (and language-like) systems.

Having shown that spontaneous production of gestures reveals a bias for isomorphism with conceptual structure we are left with an important question about the source of this bias. Is it “imposed by the nature of the human language capacity” as Adger (2017) suggests, or is this bias a result of a domain general constraint for simplicity interacting with a conceptual structure that is in principle learnable by the child from the structure of the world? To test this, we present preliminary results of an investigation of the relationships between objects, properties, numerosity, and locations using corpus statistics.

29 March: Kazuo Okanoya & Miki Takahasi

Wednesday 29 March 2017, 15:00–16:00
G15, 7 Bristo Square

Domestication and evolution of signal complexity in Bengalese finches

Kazuo Okanoya (University of Tokyo)

Among vocalizations birds make, a class of sounds that are consisted of more than two types of sound patterns arranged in a certain temporal sequence is called as a ‘birdsong’, not only because of the organization of sound patterns, but also because our musical aesthetics intuitively allow such an analogy. Scientific investigations of birdsong to date suggest that certain properties of birdsong extend beyond the musical to the developmental analogies Bengalese finches (BFs) are domesticated strains of wild white-rumped munias (WRMs) imported from China to Japan 250 years ago. BF songs are composed of multiple chunks and each chunk is a combination of 2-4 song notes. Furthermore, chunks are arranged in a finite-state probabilistic automaton. We studied how and why BFs sing such complex songs. We found the following facts. 1) The ancestral strain sing simpler songs. 2) There is high learning specificity in WRMs but not in BFs. 3) BFs have larger song control nuclei and higher level of glutamate receptor gene expressions than WRMs. 4) Both BF and WRM females prefer complex songs as measured by the nest string assay and males with complex songs are physically fitted than the males with simpler songs. These results promoted sexual selection scenario of song complexity in BFs. We further examined factors related with domestication. We examined songs of WRMs in subpopulations of Taiwan. Where there is a sympatric species to WRMs, songs were simpler. This leads to a hypothesis that in the wild songs needed to be simple to secure species identification, but under domestication this constrains was set free. We also examined socio-emotional indexes including neophobic tendency, tameness, behavioral stress reactions, and corticosterone levels. All indexes suggested that WRMs have higher level of stress and social shyness, which should be adaptive under natural environment, but could be limiting opportunities for learning complex songs. Thus, evolution of song complexity involves not only factors related with strengthen of sexual selection and relaxation of species identification, but also socio- emotional factors due to domestication. Furthermore, recent suggestion of ‘neural crest’ hypothesis that might account for the domestication syndrome fits well with the properties of Bengalese finches. These results on Bengalese finches must be useful in discussing possible biological origin of human speech in terms of proximate and ultimate factors.

The plasticity of song learning and tutor choice by cross-fostering and multiple tutor experiments in Bengalese finches.

Miki Takahasi (University of Tokyo)

The Bengalese finch (Lonchura striata var. domestica) is a domesticated strain of wild white-rumped munias (Lonchura striata). Through the domestication, the courtship songs of Bengalese finches have been differentiated from those of wild munias. The songs have tonal phonology and complex syntax in Bengalese finches, although munia songs have noisy sound with stereotyped syntax. The cross-fostering experiment revealed that there was significantly different in the accuracy of song learning between Bengalese finches and white-rumped munias. The proportion of shared elements with tutors was about 90 % regardless of tutor strain in Bengalese finches. In munias, they shared 75% song elements from the foster tutor (Bengalese finches) although they could copied almost 100% from own strain. Bengalese finches lost the accurate song learning, it will lead to increase the plasticity of song learning instead. We set a colony with eleven males and ten females of Bengalese finches and let them bred freely. Under the multiple tutor condition, most out of 32 juveniles learned parts of songs from two tutors. They segmented the songs by transition probability and combined some parts into own song. We also conducted a multiple tutor experiment in munias. 11 munia juveniles learned their father songs and only one juvenile learned from two tutors. While munias learned songs from several tutors, munias tended to learn from their familiar songs (their father). These results suggest that the accuracy of song learning is related to how many tutors juveniles select.