He establishes Adam as a real person, not a Rain Man substitute.
On rare occasions, the outcome can be highly-charged drama, most notably with Tom Hanks in Forrest Gump, Russell Crowe in A Beautiful Mind and Dustin Hoffman in Rain Man.
And while autism and Asperger syndrome have played a role in plenty of other movies, Adam isn't some Rain Man redux about a cocksure hot-shot who learns a thing or two from the guy with the alienating social impairments.
To his credit, Dancy doesn't take the showstopping Rain Man route, but, however underplayed, his Adam is all too authentic for most social intercourse.
Cynical cinemagoers will say: “Haven’t we done this before in Rain Man?” Can any actor add anything new, even if behaviourally more accurate, to Dustin Hoffman’s performance?
The mild charm of Adam and what makes it, at times, a piece of borderline kitsch is that it's an affliction movie in which the hero's handicap is so much less severe than it is in, say, Rain Man or Charly that the film frequently seems a bit daffy for placing it so front and center.