Word finding – Children with word finding difficulties may know a word, but have difficulty accessing it for production – similar to the tip of the tongue phenomenon. Pragmatics – Pragmatics refers to the ability to select the appropriate message, or interpret what others say, in relation to context. Pragmatic difficulties can give an impression of oddity, with the content of language not fitting the environmental or social context; comprehension may be over-literal; the child may chatter incessantly, be poor at turn-taking in conversation and maintaining a topic
Discourse – Discourse refers to a level of organization of language beyond the sentence. Child with limitations in this domain may have limited ability to tell a story or describe a set of events in a logical sequence
Verbal memory and learning – Problems with remembering words or sentences can affect both the learning of new vocabulary, and the understanding of long or complex sentences. Young children with DLD may say their first words later than other children. It may also take children with DLD longer to learn and remember novel words. Phonology – Phonology is the branch of linguistics concerned with the way sounds are combined in words. Children with difficulties with phonology may fail to distinguish between certain speech sounds, such as t and k, so that cake is produced as tate. Such difficulties are not unusual as part of typical development in toddlers, but they would usually resolve by the time children are 4–5 years old.
However, subsequent studies have found that, though DLD runs in families, it is not usually caused by a mutation in FOXP2 or another specific gene. Current evidence suggests that there are many different genes that can influence language learning, and DLD results when a child inherits a particularly detrimental combination of risk factors, each of which may have only a small effect. Nevertheless, study of the mode of action of the FOXP2 gene has helped identify other common genetic variants involved in the same neural pathways that may play a part in causing DLD.Language disorders are associated with aspects of home environment, and it is often assumed that this is a causal link, with poor language stimulation leading to weak language skills. Twin studies, however, show that two children in the same home environment can have very different language outcomes, suggesting we should consider other explanations for the link. Children with DLD often grow up into adults who have relatively low educational attainments, and their children may share a genetic risk for language disorder.One non-genetic factor that is known to have a specific impact on language development is being a younger sibling in a large family. Associated factors
It has long been noted that males are more affected by DLD than females, with a sex ratio of affected males-to-females around 3 or 4:1. However, the sex difference is much less striking in epidemiological samples, suggesting that similar problems may exist in females but are less likely to be detected.