common in cases where comprehension as well as expressive language is affected. There is also evidence that scores on tests of nonverbal ability of children with DLD decrease over the course of development. DLD is associated with an elevated risk of social, emotional and mental health concerns. For instance, in a UK survey, 64% of a sample of 11-year-olds with DLD scored above a clinical threshold on a questionnaire for psychiatric difficulties, and 36% were regularly bullied, compared with 12% of comparison children. In the longer-term, studies of adult outcomes of children with DLD have found elevated rates of unemployment, social isolation and psychiatric disorder among those with early comprehension difficulties. However, better outcomes are found for children who have milder difficulties and do not require special educational provision. Prevalence Epidemiological studies of children in the US and the UK converge in estimating the prevalence of DLD in five-year-olds at around 7%. Recently, an Australian population based study demonstrated comparable prevalence of DLD amongst 10 year-old children. Therefore, the prevalence is about one in every 15 children. By these statistics, in a classroom of 30 students, 2 would have DLD. In research by Tomblin et al., prevalence of DLD in racial/ethnic groups was highest in Native Americans, with African Americans being the next highest, followed by Hispanic people, and then White people. No students of Asian descent presented with DLD; however, other research does indicate that DLD is present in children of Asian descent. Research Much research has focused on trying to identify what makes language learning difficult for some children. A major divide is between theories that attribute the difficulties to a low-level problem with auditory temporal processing, and those that propose there is a deficit in a specialised language-learning system. Other accounts emphasise deficits in specific aspects of learning and memory. It can be difficult to choose between theories because they do not always make distinctive predictions, and there is considerable heterogeneity among children with DLD. It has also been suggested that DLD may only arise when more than one underlying deficit is present. Developmental language disorder in adults Relatively little research has been conducted to test the outcomes of DLD in adults. In a study comparing 17 men with DLD to siblings without DLD, researchers found that the DLD men had normal intelligence with higher performance IQ than verbal IQ. The participants still exhibited a severe and