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"The origins of gestural imitation: insights from evolution, development and cultural transmission"

Final Report Summary - GESTRANSCULT (The origins of gestural imitation: insights from evolution, development and cultural transmission)

The ability to copy others lies at the heart of our capacity to learn languages, social rules and acquire material culture. While imitation is a core feature of human life, understanding how it evolved, how it develops and the role cultural transmission plays are not fully understood. The goal of this research was to investigate the origins of gestural imitation from evolutionary, developmental and cultural perspectives.

To address this question, the research was divided into three main objectives:

Objective 1: Investigating the evolution of gestural imitation: Can bonobos, a species of great ape, imitate gestural actions?
Imitation represents a core component of what it means to be human; it underlies our capacity for acquiring and transmitting cultural behaviours, which includes language, material culture, social rituals and conventions. An unresolved debate is whether humans are unique in their skills for imitation or whether these capacities are shared with our closest living relatives, the great apes. In this study, we addressed this by investigating the copying abilities of our closest living great ape relatives, the bonobos, in comparison to that of human children.
We compared the gestural imitation behaviour of bonobos living in a forested Sanctuary in Africa, to that of 3-5 year old human children that were visitors to a UK Science Museum. Participants observed a demonstrator perform gestural actions over a box, before it was opened to reveal a reward. We explored whether bonobos and/or children would spontaneously imitate what they had seen. The results show striking species differences: children readily copied the actions, whereas the great apes did not copy at all. The tendency for children to imitate likely represents a critical piece of the puzzle as to why human cultures differ so profoundly from those of great apes. By copying even actions that we don’t fully understand, humans can rapidly acquire and spread new forms of culture and adopt group behaviours, such as rituals and conventions. This study provides key insights into the evolution of imitation and why human cultures differ profoundly from those of animals.

Objective 2. The development of gestural imitation in young children
Imitation represents a core component of the human cultural capacity and underlies many of traits that are thought to characterise our species, including learning languages. Learning a language or communication system requires faithful transmission of communicative conventions, as unless these are shared between users, they are meaningless. Although imitation develops early in childhood, much of the focus on understanding children’s imitation has been focussed on object related behaviour involving tools, or more recently, social rules and conventions. These studies have shown that children readily imitate behaviours that have no obvious function. This phenomenon, known as over-imitation is thought to explain some of the key differences between human cultures and animal cultures. Although imitation is involved in language learning, there is surprisingly little work on how communication is shaped through the imitative tendencies of children and how this relates to other forms of imitation. To address this, we used a single integrative paradigm to investigate several factors proposed to shape children’s imitation within communicative and cultural contexts. We compared 4-6 year old children in a gestural imitation task involving actions that were verbally-framed as being communicative, instrumental, socially conventional in function. We also explored whether context influenced which types of actions children would copy. Results showed that children were overall more likely to imitate actions that were framed as being ‘socially conventional’, and were equally likely to copy actions that were framed as being communicative or instrumental. Young children were more likely to imitate actions that were rooted to objects rather than in the air. Our results show that children of all ages are highly sensitive to even minimal cues as to the context, and flexibly adapt their imitation accordingly. We found a close relation between the copying of actions framed as gestures as those framed as instrumental, highlighting the close interplay in the development of tool use and language. Overall, this study suggests that a complex composite of factors shape children’s imitation, which varies across the age span.

Objective 3. How does cultural transmission shape the structure of gesture: A diffusion chain experiment
Recent studies have highlighted the role that the transmission process itself plays in shaping the evolution of language and culture. One recent study examined how the structure of an artificial written language evolved as it was progressively learned and transmitted along a chain of learners. When the language was transmitted across generations, it spontaneously became more structured, language-like and easier to learn. Although the findings are important, this study focused on the transmission of a ‘written’ language, which is a modern medium to communicate, compared to more evolutionary ancient forms, such as vocalisations and gestures. In this study, we address this by using a diffusion chain experiment to examine whether language-like structure also emerges within a gestural system. By doing so, this study provides a sounder framework to explore how transmission shapes language evolution.
In the diffusion chain experiment, the first participant observed target stimuli which were randomly paired with a set of gestures. The stimuli had three features – shape, colour and movement direction. After training, the participant was asked to replicate the gestures that they thought matched the stimuli. Their responses were videoed and used as the stimuli for a second participant, and so on. This process enabled the diffusion of behavior to be observed as it passed along a chain. The results indicated that, unlike written language, the gestural language did not readily acquire systematic structure or become easier to learn. The results are important as they suggest that the transmission of gestural languages may require scaffolding from other contextual features, such as social interaction, in order for complex information to be reliably transmitted. In a follow up, we plan to re-run this study in order to find the minimal level of complexity possible for a gestural system to be faithfully transmitted as well as the intervening role of social interaction. Although we did not find that the gestures evolved into a language-like form, the results provide important insight into what features are required to be in place for languages to evolve.

In addition to achieving these research objectives, this Fellowship has represented a fantastic training opportunity for the Fellow’s professional development. As a result of this project, the Fellow has acquired a vast array of valuable and transferable skills to help develop her future research career. This includes, but is not limited to, developing new expertise in experimental design, developing rigorous and ethical protocols for conducting developmental research with children and adults, establishing new collaborations, acquiring skills in teaching and mentoring and developing a strong skill-set in public outreach and dissemination.
Contact: zanna.e.clay@durham.ac.uk