Handwriting: Are adults who write in a mixture of upper- and lower-case letters suffering from some kind of learning disability, or simply poorly educated?

This makes me laugh.  I'm guilty, but it's not a learning issue it's just my printing.  My cursive is stronger and preferred, yet there are times that I'm printing.  When I am printing and in a hurry, there are times when I'm trying to balance neatness, concept and letters (as well as not slipping into cursive!)  I've seen it before- at times capital letters show up.  I don't usually bother to correct them. I think it's because many adults learned to write with capital letters alone even though they should learn upper and lower case.

One of my colleagues and I both do this.  We both have PhDs (his is from Purdue, mine UTK).  My findings suggest that when we are writing on the whiteboard or on paper (NOT typing), are that neuroscience field specialists suggest the firing of neurons faster than we can cognitively process. So, to compensate for not missing information to be presented, the item, at least in this case, is the thinking how the words would appear.  The other thing my colleagues and I have in common is that our writing on the board is less than high quality -- but it is legible. I wish I could cite some of my findings, but I don't recall the sites -- I did find the via http://scholar.google.com though.

As a future English teacher, my take on it is that some people, thinking that writing is a more 'serious' than speech, capitalize inappropriately because they don't understand completely that you capitalize proper nouns. They just notice that when something is 'important', it is capitalized, and so their capitalization leaks into other words in an attempt to make their writing seem more professional. I have personally seen this more on social media than in handwriting--particularly when people are arguing over and the mis-capitalization is used in an attempt to give their statement the authority that comes from a bit more formality.

These are great answers! I wanted to point out another possibility. Do you remember the "CAPS lock" debate in internet chat rooms and social media? It was determined that a large percentage of these "shouting" people suffered from poor vision, so having CAPS lock on allowed them to see what they were typing. In some cases, as is the case with my boyfriend (who has poor vision), the use of uppercase letters at the beginning of each word helps to differentiate where one word stops and the next word starts. The same is true with punctuation when a space is put between the word and punctuation mark (do you know how hard it is to tell the difference between a comma and a period at the end of a word when you can't see clearly?) However, I have seen cases where it is an issue with brain chemistry (aka mental disability) and cognitive function (aka learning disability). Most adults have learned to cope by using uppercase at the beginning of each word. Sadly, many people are not tolerant of such coping mechanisms and spew hatred for it's use.

From Lee Dein: Creator of The Magic Link Handwriting ProgrammeHaving taught thousands of pupils I have often seen examples of random capital letters interspersed in sentences. In almost all cases it is simply because letter formation has not been taught in a simple a s structured way resulting in confusion. There are too many complicated fonts and teachers are not consistent about which to use. Highly intelligent people may insert capitals randomly and this can easily be improved through teaching a simple cursive style and encouraging proofreading. http://www.magiclinkhandwriting.com

My dad is quite intelligent. Completed most of master's degree. His handwriting is atrocious and he mixes in capitals freely. He wonders if he might have dysgraphia. He also often feels like he doesn't communicate well otherwise. He does also have very poor vision.

In general writing (sentence/paragraph): We all have different styles of writing, and some (me) choose not to care about upper-lower cases in favor of beautiful scripting, flow of thoughts/words, or different set of rules we apply in our writing. Edit: The amount of time the person spends either writing with the pen or typing on the keyboard is also factor. If a person solely uses typing as the method of communication, his skills as a writer by pen may deteriorate from un-use. Also, the writing instrument is a major factor. ie. If you are given a marker or sharpie, you will most likely write in print. If you are given a fountain pen, you will most likely write in a scripting cursive manner because fountain pens offer littler resistance on paper.