Literacy between the genders in early 19th century

[jones9]

In one of the families I'm researching, I have found that the father and two sons signed their documents with a cross (hinting at illiteracy?), yet one son and the three daughters all appear to be literate as they have written their own signatures (I have a few examples of their signatures which are in their handwriting) - this remains constant from about 1820s-70s

Has anyone come across anything similar/suggest a reason for this? Would the men be literate but prefer to make a mark or something?

I ask because I'm pretty sure that the father of this man and his family (generation back) was able to read and has signed his signature!

Thanks for suggestions,
jones9

[groom]

I wonder if being able to sign your name makes you literate, it could be that was all they were able to do?

What was the occupation of the men, was it one where they wouldn't have been required to have had much schooling?