Pinheads!--I saw the movie Freaks the other day!

I saw the 1932 cult classic Freaks the other day and
it raised a couple of questions.

What exactly is “pinheadism”? Is it the same as microcephaly? (For what follows I’m assuming that it is.) And how intelligent roughly speaking would
these unfortunates be? Most of us are fairly familiar with
Down’s Syndrome, but you almost never hear of microcephaly.
I note that the comic strip Zippy the Pinhead is published
in many papers, without any microcephalic-advocacy group
complaining. This tells me that they must be practically nonexistent today.

In the movie I was interested to note that the genuine microcephalics who appeared in the movie could talk. Granted they couldn’t discuss the common thread of English humor from P.G. Wodehouse through Douglas Addams, but they
could talk well enough to communicate. This interested me
because their crania couldn’t have been much bigger than
that of a Homo habilis or Homo erectus, and
no one is really sure if those two species had the power of speech. What I saw in the movie indicates that if these prehistoric species had the anatomical equipment to speak,
then they probably had the brain power as well.

Comments? Any experts in the field out there?