Language-wise, it's kind of a mixed bag. How much do social things like sarcasm matter for 'language skills'? And how Williams syndrome leads to sociability and lack of racism is very interesting; following extract dump from https://www.nytimes.com/2007/07/08/magazine/08sociability-t.html?reddit

People with Williams tend to lack not just social fear but also social savvy. Lost on them are many meanings, machinations, ideas and intentions that most of us infer from facial expression, body language, context and stock phrasings. If you’re talking with someone with Williams syndrome and look at your watch and say: “Oh, my, look at the time! Well it’s been awfully nice talking with you . . . ,” your conversational partner may well smile brightly, agree that “this is nice” and ask if you’ve ever gone to Disney World. Because of this — and because many of us feel uneasy with people with cognitive disorders, or for that matter with anyone profoundly unlike us — people with Williams can have trouble deepening relationships. This saddens and frustrates them. They know no strangers but can claim few friends....Like most people with Williams, Nicki loves to talk but has trouble getting past a cocktail-party-level chatter. Nicki, however, has fashioned at least a partial solution. “Ever since she was tiny,” Verna Hornbaker told me, “Nicki has always especially loved to talk to men. And in the last few years, by chance, she figured out how to do it. She reads the sports section in the paper, and she watches baseball and football on TV, and she has learned enough about this stuff that she can talk to any man about what the 49ers or the Giants are up to. My husband gets annoyed when I say this, but I don’t mean it badly: men typically have that superficial kind of conversation, you know — weather and sports. And Nicki can do it. She knows what team won last night and where the standings are. It’s only so deep. But she can do it. And she can talk a good long while with most men about it.”...In Williams the imbalance is profound. The brains of people with Williams are on average 15 percent smaller than normal, and almost all this size reduction comes from underdeveloped dorsal regions. Ventral regions, meanwhile, are close to normal and in some areas — auditory processing, for example — are unusually rich in synaptic connections. The genetic deletion predisposes a person not just to weakness in some functions but also to relative (and possibly absolute) strengths in others. The Williams newborn thus arrives facing distinct challenges regarding space and other abstractions but primed to process emotion, sound and language....This window is longer than that for most infants, as Williams children, oddly, start talking a year or so later than most children...Cognitive scientists argue over whether people with Williams have theory of mind. Williams people pass some theory-of-mind tests and fail others. They get many jokes, for instance, but don’t understand irony. They make small talk but tend not to discuss the subtler dynamics of interpersonal relationships. Theory of mind is a slippery, multilayered concept, so the debate becomes arcane. But it’s clear that Williamses do not generally sniff out the sorts of hidden meanings and intentions that lie behind so much human behavior....“And the most important abnormalities in Williams,” he says, “are circuits that have to do with basic regulation of emotions.” The most significant such finding is a dead connection between the orbitofrontal cortex, an area above the eye sockets and the amygdala, the brain’s fear center. The orbitofrontal cortex (or OFC) is associated with (among other things) prioritizing behavior in social contexts, and earlier studies found that damage to the OFC reduces inhibitions and makes it harder to detect faux pas. The Berman team detected a new contribution to social behavior: They found that while in most people the OFC communicated with the amygdala when viewing threatening faces, the OFC in people with Williams did not. This OFC-amygdala connection worked normally, however, when people with Williams viewed nonsocial threats, like pictures of snakes, sharks or car crashes.