Individual Differences in Comprehension across the Lifespan

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The ability to communicate using spoken language is a core human ability. Language provides the foundation for social and educational development and without strong language skills, people struggle to participate positively in society. Spoken language allows us to rapidly transfer ideas from the mind of the speaker to the mind of the listener. This transfer relies on the ability of the listener to quickly access the meaning of each word that they hear: they must make 'best guesses' about the intended meaning of each word. The ability to rapidly and accurately understand the meanings of spoken words is vital, not only for communication using spoken language, but also to provide the foundation for skilled reading comprehension.Accessing the meanings of words is made more difficult by the presence of 'lexical ambiguity': words that can refer to more than one concept. For example, when accessing the sentence "What an enormous trunk!" the listener must work out whether the speaker was referring to an elephant's nose, a large suitcase, a car's boot, or the main stem of a tree.The ability to accurately and rapidly disambiguate word meanings is vital for communication: approximately 80% of common words in English have multiple dictionary definitions. Take for example the first sentence of the text given to 11-year-old children across England as part of the national curriculum tests: "Dawn was casting spun-gold threads across a rosy sky over Sawubona game reserve". The words in this sentence have on average 8.8 dictionary definitions: children must, for example, work out that "Dawn" does not refer to a girl's name and that "game" does not refer to a competitive sport. In addition, "cast" and "threads" do not refer to physical actions or objects, but have more metaphorical interpretations.While many of us are able to accurately disambiguate most words without obvious effort, research has revealed large individual differences in this skill: some people are slower and more error prone and the same people also tend to perform poorly tests of comprehension more generally. This project aims to uncover the causes of these difficulties as a first step to identifying how best to help them in the classroom or clinic. This is important as poor language comprehension is associated with difficulty learning to read, with social and emotional unhappiness and with poor behaviour.The current research will develop novel child-friendly methods for assessing the ability to understand spoken sentences containing ambiguous words. We will use these methods to discover the factors that contribute to individual differences in the ability to understand words. We will test two types of explanation. The first sees linguistic factors as critical - qualitative or quantitative differences in the stored knowledge a person has about word meanings. The second type of explanation is that people differ in how flexible they can be in selecting and switching between alternative meanings, rather than their knowledge of the meanings themselves. We will use computational models and experimental methods to assess how these factors work together to bring about comprehension. Finally, we will move from the laboratory to the classroom to conduct an intervention study in primary age children to assess whether comprehension can be enhanced by playing word games while listening to carefully constructed stories.Answers to these questions are critical for efforts to improve comprehension skills in school aged children. The National Curriculum sees language and communication as essential for educational achievement, and considerable teaching time is devoted to improving performance in national tests. Unfortunately, evidence-based teaching strategies for improving comprehension are not well-developed, certainly in comparison with those in place for word reading. This research will provide the theoretical framework and empirical basis for larger scale interventions.