By learning to read and write upside down, what did I do to myself? If you've ever read Encyclopedia Brown books, you'll be familiar with the backwards writing in the back of the book that explains the solution to the case.

When I was in my mid-late teens (I don't remember the age exactly) I decided to teach myself to read/write upside down (and backwards?). I can read most text fairly well when the page is upside down (and have no problems with the upside down unicode text people post on Facebook), and I am able to write upside down with relative ease.

However, since developing that skill I have fairly extreme difficulties remembering how to write lowercase b's and d's, and I've had to use a trick I've heard dyslexics use and I remind myself that a 'b' points towards the end of a word.

I have no problems reading words with the characters, or typing them on the computer when I want a 'b' or a 'd', only when I'm writing it.

Did I give myself a very limited form of dyslexia?
Negative Transfer

A common scientific term to describe what you are talking about is called negative transfer. I.e., where learning one skill actually results in lower performance on another skill. This is contrasted with positive transfer, when learning one skill facilitates performance on another skill. In general (although I don't have refs on hands) positive transfer is generally a greater effect than negative transfer. Negative transfer tends to be localised to particular aspects of the task (e.g., b's and d's).

For a extended encyclopedia entry see Perkins and Salomon's (1992) article on transfer of learning.

Research on Mirror Reading and Writing

There's even research specifically on reading and writing upside down and back to front (e.g., see google scholarfor 'mirror writing' and 'mirror reading'). I haven't read much of this literature.

To take but one article, Gottfried, Sancar, and Chatterjee (2003) discuss acquired mirror writing.

They note, perhaps relevant to your question, that:


  Young children, developmental dyslexics, and some healthy left-handed
  adults may produce mirror text.


I assume that in the above cases (as opposed to your case where it is acquired with deliberate practice), writing in reverse is involuntary, in which case I suppose you could describe writing a few letters back to front involuntarily as representing a symptom shared with some developmental dyslexics.

As an interesting historical aside, they note that


  Perhaps the most celebrated mirror writer, Leonardo da Vinci,
  generated over 5000 notebook pages in reverse.


So, you're in good company.

References


Gottfried, J., Sancar, F., and Chatterjee, A. (2003). Acquired mirror
writing and reading: evidence for reflected graphemic representations.
Neuropsychologia, 41(1):96-107. FREE PDF
Perkins, D. and Salomon, G. (1992). Transfer of learning. International
encyclopedia of education. FREE LINK