Reward and motivation mechanisms supporting language learning: a cross-syndrome investigation of Developmental Language Disorder (DLD) and autism

Developmental language disorder (DLD) and autism are two common neurodevelopmental conditions in which language acquisition is disrupted. Autism affects how children communicate and interact with the world. One in every 100 children has autism, and 70% of autistic children face lifelong language difficulties. DLD is a neurodevelopmental condition characterised by persistent difficulties with understanding and using language. Two children in every classroom are estimated to have DLD. Language difficulties have a severe impact on these children's life outcomes, limiting academic achievement, job prospects, and social and emotional well-being. One factor that could facilitate learning - or exacerbate impairments - is motivation. Children with these conditions often do not enjoy, or pursue, language-based tasks such as reading. This creates a vicious cycle: those who are not good at language disengage from language, and consequently, they struggle to get better at language. Yet, current cognitive models of these two conditions largely neglect the role of motivation. Understanding how to enhance language learning by improving motivation could help us achieve better outcomes from existing or novel interventions. In this project, I focus on the links between motivation and language learning, and their disruption in DLD and autism.

Recent advances in methods, particularly in brain imaging and mathematical modelling, now allow us to understand motivation in far greater depth. We can ask which things people find intrinsically rewarding, and quantify how much effort they will exert to obtain them. Crucially, these studies reveal motivation can enhance learning. I plan to use these advanced approaches to study motivation for language learning in DLD and autism for the first time. I will examine if children with DLD and autism find language learning intrinsically rewarding, and if states of intrinsic motivation can be used to improve learning. I will also examine the role of external social and non-social rewards for language learning, assessing if conferred benefit differs in DLD and autism. Finally, I will develop a new task to quantify effort, and assess whether people with DLD or autism perceive language learning as less worthy of effort than neurotypical people. This work will help us understand what changes we might need to make to the learning environment to support language learning for these children.

In other populations (e.g. ADHD, Parkinson's disease), differences in motivation have been linked to specific circuits in the brain. We propose to use similar imaging techniques to examine brain structure and function in the neural regions involved in language processing and motivation. This will help us understand which regions or networks might be disrupted in DLD and autism, and give us greater insight into the differences between groups (for instance, different regions may be disrupted in DLD and autism). Additionally, both children with DLD and those with autism who have language difficulties are understudied from a neuroscientific standpoint, so this work will also yield important information about language processing in these groups.

In summary, reward and motivation play a crucial role in learning, across a variety of tasks and across species. Yet, their role in language learning is under-studied. Using state-of-the-art methods, I will study the interaction between language processing and reward and motivation systems in DLD, autism, and typical development. This will give us insight into motivation for language learning, shedding light on whether methods that are effective for neurotypical children hold in DLD and autism. Further, by understanding specific brain disruptions in these groups, we will be able to advance our knowledge of the biological differences underlying these two conditions. Ultimately, we can develop more targeted intervention to boost language learning, improving life outcomes in these groups.

Research has traditionally focused on cognitive and linguistic factors that might cause the language difficulties faced by children with DLD or autism. However, an important everyday factor that could affect language outcome is motivation. Motivation is known to improve short-term learning and long-term retention. Current language intervention assumes the effects of rewards and motivation do not vary across children, yet strategies that are effective for neurotypical children may not work well for children with neurodevelopmental disorders. Understanding motivation-learning links in these groups is an important first step towards optimising language interventions. Here, I will take a multimodal approach to understanding motivation for language learning in DLD and autism, using state-of-the-art behavioural paradigms, brain imaging, and computational modelling. By systematically conducting cross-syndrome comparisons across autism and DLD, I will be able to determine mechanistic alterations in the links between motivation and language learning in these two groups, and understand how difficulties are related to language processing. First, I will study the effects of motivation on language learning in DLD and autism, focusing on the role of extrinsic and intrinsic reward. Second, I will quantify the cost-benefit valuations people engage in when performing language tasks through developing an effort-based discounting task with linguistic stimuli. Finally, I will characterise how motivation affects brain systems for language, to gain specific insight into the processes that may be disrupted in autism and DLD (valuation, acting on valuations, reward-memory links). Ultimately, this comprehensive programme can help us identify incentives that boost language learning, and determine if incentives need to differ across different developmental populations.