Semantic Pragmatic Disorder is what Pragmatic Language Impairment (PLI) used to be called, It’s still considered a communication disorder in DSM-V. There was some scientific quarrelling about whether or not ‘Semantic’ was an appropriate inclusion:
In reality, speech and language therapists (SLTs) rarely use the term SPD to describe a distinct condition any more, as it is now generally agreed that there is little correlation between semantic and pragmatic behaviours as such: they can exist together but not necessarily. Therefore many people have dropped the “semantic” part of the label in favour of “pragmatic language impairment” (PLI) which describes the difficulty of using communicative language appropriately.
PLI is an impairment often associated with Autism Spectrum Disorder where someone lacks a ‘pragmatic’ understanding of the language. The pragmatics of the language are how context contributes to meaning and how certain things can be implied rather than actually said. Even without an impairment sometimes these turns of phrase or metaphors can be difficult to pick up on, especially if they are foreign. For example, if I tell you “Mary was given a horse” you’re brain probably won’t think that Mary is pregnant because the phrase is archaic and out of fashion.
Someone suffering from a PLI might take everything you say quite literally and not understand the subtext. So if you tell someone “You have the green light” they’re more likely to think a green lantern has manifested nearby than realised you mean that they are allowed to do the thing. God forbid you tell them it is “Raining cats and dogs”.
Many children suffering from PLI are described as using verbose language. Something that may remind you of Hans Asperger’s ‘Little Professors’. They can often speak quite well and only run into difficulties when it comes to jokes, metaphors, idioms, and puns, which when literally interpreted are often meaningless and nonsensical.
Previous ‘Semantic Pragmatic Disorder’ was not a separate entity to autism at all. This changed after a substantial number of children exhibited symptoms of the disorder but without meeting the threshold for ASD.
See Also:
What is alexithymia? What causes it and what treatments are available?