One of the most enduring narratives of sideshow culture, for good or ill, is the 1932 Tod Browning movie "Freaks." Featuring real performers from popular circus acts or sideshows, the film introduced several characters with abnormally small heads. And let's just get it out of the way right now: The "pinhead" description used in the movie is not acceptable nomenclature these days.
The condition is called microcephaly, which occurs when the head is smaller than would be expected in normal development. It's important to note that primary microcephaly might result in intellectual disabilities or developmental issues, but it can also be a symptom (secondary microcephaly) of another condition like Down syndrome [source: Mayo Clinic].
Primary microcephaly is rare: It's estimated to occur in one in 40,000 live births [source: Minnesota Dept. of Health]. And while it's true that microcephaly could lead to cognitive impairment, it doesn't preclude normal or high-functioning development. Children born with microcephaly have a huge range of long-term outcomes and overall function.