Language adapts: exploring the cultural dynamics of iterated learning

Human languages are not just tools for transmitting cultural ideas, they are themselves culturally transmitted. This single observation has major implications for our understanding of how and why languages around the world are structured the way they are, and also for how scientists should be studying them. Accounting for the origins of what turns out to be such a uniquely human ability is, and should be, a priority for anyone interested in what makes us different from every other lifeform on Earth. The way the scientific community thinks about language has seen considerable changes over the years. In particular, we have witnessed movements away from a purely descriptive science of language, towards a more explanatory framework that is willing to embrace the difficult questions of not just how individual languages are currently structured and used, but also how and why they got to be that way in the first place. Seeing languages as historical entities is, of course, nothing new in linguistics. Seeing languages as complex adaptive systems, undergoing processes of evolution at multiple levels of interaction however, is. Broadly speaking, this thesis explores some of the implications that this perspective on language has, and argues that in addition to furthering our understanding of the processes of biological evolution and the mechanisms of individual learning required specifically for language, we also need to be mindful of the less well-understood cultural processes that mediate between the two. Human communication systems are not just direct expressions of our genes. Neither are they independently acquired by learners anew at every generation. Instead, languages are transmitted culturally from one generation to another, creating an opportunity for a different kind of evolutionary channel to exist. It is a central aim of this thesis to explore some of the adaptive dynamics that such a cultural channel has, and investigate the extent to which certain structural and statistical properties of language can be directly explained as adaptations to the transmission process and the learning biases of speakers. In order to address this aim, this thesis takes an experimental approach. Building on a rich set of empirical results from various computational simulations and mathematical models, it presents a novel methodological framework for exploring one type of cultural transmission mechanism, iterated learning, in the laboratory using human participants. In these experiments, we observe the evolution of artificial languages as they are acquired and then transmitted to new learners. Although there is no communication involved in these studies, and participants are unaware that their learning efforts are being propagated to future learners, we find that many functional features of language emerge naturally from the different constraints imposed upon them during transmission. These constraints can take a variety of forms, both internal and external to the learner. Taken collectively, the data presented here suggest several points: (i) that iterated language learning experiments can provide us with new insights about the emergence and evolution of language; (ii) that language-like structure can emerge as a result of cultural transmission alone; and (iii) that whilst structure in these systems has the appearance of design, and is in some sense ‘created’ by intentional beings, its emergence is in fact wholly the result of non-intentional processes. Put simply, cultural evolution plays a vital role in language. This work extends our framework for understanding it, and offers a new method for investigating it

Iterated learning with human subjects : an empirical framework for the emergence and cultural transmission of language

The study of language evolution has benefited enormously from the contribution made by computational simulations of the cultural transmission of language over the past ten years. However, we still have not explored or confirmed these findings empirically in a human population. This thesis presents a novel experimental method for investigating the emergence and cultural transmission of language under controlled laboratory settings. By integrating techniques from the modelling of iterated learning, with techniques used to investigate language acquisition via artificial language learning, a suitable empirical framework is created, opening up new avenues of research for understanding human language and culture

Identifying innovation in laboratory studies of cultural evolution: rates of retention and measures of adaptation

In recent years, laboratory studies of cultural evolution have become increasingly prevalent as a means of identifying and understanding the effects of cultural transmission on the form and functionality of transmitted material. The data sets generated by these studies may provide insights into the conditions encouraging, or inhibiting, high rates of innovation, as well as the effect that this has on measures of adaptive cultural change. Here we review recent experimental studies of cultural evolution with a view to elucidating the role of innovation in generating observed trends. We first consider how tasks are presented to participants, and how the corresponding conceptualisation of task success is likely to influence the degree of intent underlying any deviations from perfect reproduction. We then consider the measures of interest used by the researchers to track the changes that occur as a result of transmission, and how these are likely to be affected by differing rates of retention. We conclude that considering studies of cultural evolution from the perspective of innovation provides valuable insights which help to clarify important differences in research designs, which have implications for the likely effects of variation in retention rates on measures of cultural adaptatio

Compression and communication in the cultural evolution of linguistic structure

Language exhibits striking systematic structure. Words are composed of combinations of reusable sounds, and those words in turn are combined to form complex sentences. These properties make language unique among natural communication systems and enable our species to convey an open-ended set of messages. We provide a cultural evolutionary account of the origins of this structure. We show, using simulations of rational learners and laboratory experiments, that structure arises from a trade-off between pressures for compressibility (imposed during learning) and expressivity (imposed during communication). We further demonstrate that the relative strength of these two pressures can be varied in different social contexts, leading to novel predictions about the emergence of structured behaviour in the wild

Sequence memory constraints give rise to language-like structure through iterated learning

Human language is composed of sequences of reusable elements. The origins of the sequential structure of language is a hotly debated topic in evolutionary linguistics. In this paper, we show that sets of sequences with language-like statistical properties can emerge from a process of cultural evolution under pressure from chunk-based memory constraints. We employ a novel experimental task that is non-linguistic and non-communicative in nature, in which participants are trained on and later asked to recall a set of sequences one-by-one. Recalled sequences from one participant become training data for the next participant. In this way, we simulate cultural evolution in the laboratory. Our results show a cumulative increase in structure, and by comparing this structure to data from existing linguistic corpora, we demonstrate a close parallel between the sets of sequences that emerge in our experiment and those seen in natural language

Disability, violence, and mental health among Somali refugee women in a humanitarian setting

Background There is limited evidence on the relationship between disability, experiences of gender-based violence (GBV), and mental health among refugee women in humanitarian contexts. Methods A cross-sectional analysis was conducted of baseline data (n = 209) collected from women enrolled in a cohort study of refugee women accessing GBV response services in the Dadaab refugee camps in Kenya. Women were surveyed about GBV experiences (past 12 months, before the last 12 months, before arriving in the refugee camps), functional disability status, and mental health (anxiety, depression, post-traumatic stress), and we explored the inter-relationship of these factors. Results Among women accessing GBV response services, 44% reported a disability. A higher proportion of women with a disability (69%) reported a past-year experience of physical intimate partner violence and/or physical or sexual non-partner violence, compared to women without a disability (54%). A higher proportion of women with a disability (32%) experienced non-partner physical or sexual violence before arriving in the camp compared to women without a disability (16%). Disability was associated with higher scores for depression (1.93, 95% confidence interval (CI) 0.54–3.33), PTSD (2.26, 95% CI 0.03–4.49), and anxiety (1.54, 95% CI 0.13–2.95) after adjusting for age, length of encampment, partner status, number of children, and GBV indicators. Conclusions A large proportion of refugee women seeking GBV response services have disabilities, and refugee women with a disability are at high risk of poor mental health. This research highlights the need for mental health and disability screening within GBV response programming

A "novel" reading therapy programme for reading difficulties after a subarachnoid haemorrhage

Background: Although several treatments for acquired reading difficulties exist, few studies have explored the effectiveness of treatment for mild reading difficulties and treatment for reading difficulties associated with cognitive impairment. Aims: This study explored the effectiveness of an individual strategy-based reading treatment of 11 sessions given to a female participant (IW) who had mild reading difficulties following a subarachnoid haemorrhage (SAH). The impact of treatment on reading ability, confidence and emotions associated with reading were investigated. Methods & Procedures: Treatment focussed on the use of strategies to support IW’s memory when reading books, the use of a checklist to select appropriate reading materials, and increasing IW’s confidence in discussing the book she was reading with others. A person-centred approach and personally relevant materials were used throughout the treatment. Reading ability was assessed using the Gray Oral Reading Tests (GORT-4; Lee Wiederholt & Bryant, 2001), and IW’s perspective was obtained using the Reading Confidence and Emotions Questionnaire (RCEQ; see Cocks et al., 2010. Pre-treatment, post-treatment and maintenance (7 weeks post) assessments were undertaken, with an additional exit interview at the final time point. Outcomes & Results: Gains were noted in reading rate, accuracy, comprehension, and confidence, with parallel increased pleasure gained from reading and reduced negative emotions and frustration. Self-reported gains included conversing with others about material read, verbal communication, and re-engagement with the identity of being a reader. Conclusions: Strategy-based treatment resulted in positive gains in reading for pleasure, conversation, and identity, for an individual with mild chronic reading difficulties. Participant self-report and interview reveal the true value of this treatment for the individual. The positive results suggest that further research is warranted that investigates the effectiveness of strategy-based reading therapy approaches for others with acquired reading difficulties

Systems from Sequences: an Iterated Learning Account of the Emergence of Systematic Structure in a Non-Linguistic Task

Systematicity is a basic property of language and other culturally transmitted behaviours. Utilising a novel experimental task consisting of initially independent sequence learning trials, we demonstrate that systematicity can unfold gradually via the process of cultural transmission