When does an abbreviation become a word? and related questions

An experiment is reported in which subjects previously naive to text editing learned to use a set of editing commands. Some subjects used abbreviations from the beginning. Others began by using full command names, then switched to the (optional) use of abbreviations, either of their own devising or of our selection. We found significant differences in the number and nature of the errors produced by subjects in the different conditions. People who created their own abbreviations did most poorly, and did not appear to learn from this experience. Those who used abbreviations from the start were more likely to fall into error through misrecalling the referent names. The results suggest aspects of the underlying cognitive representations, with implications for the design of software interfaces.