Craniology and the Size of Helen Keller's Head

I'm reading The Story of My Life by Helen Keller and just came across an interesting couple of passages. This part is taken from Anne Sullivan's letters.

Helen's head measures twenty and one-half inches, and mine measures twenty-one and one-half inches. You see. I'm only one inch ahead!

I thought at first I misread it and she was referring to height, but no, it was just as you see above.

Then, just a little further on, in a different letter, she writes:

She will be seven years old the twenty-seventh of this month. Her height is four feet one inch, and her head measures twenty and one-half inches in circumference, the line being drawn round the head so as to pass over the prominences of the parietal and frontal bones. Above this line the head rises one and one-fourth inches.

And then she just goes on, no further explanation needed--at least not for her intended reader.

I was amused and thought this might be phrenology, a debunked pseudoscience popular back in Helen Keller's times, but my recollection was that phrenology was the study of the bumps on the head. Looking a little further, I'm guessing it is actually craniology, explained in Wikipedia as "A large skull meant a large brain and high intellectual capacity, and a small skull indicated a small brain and decreased intellectual capacity."

Do you ever wonder what people in the future will look back on in this age and laugh about?