nguage Changes and the Principle of Least Effort
"One explanation for linguistic change is the principle of least effort. According to this principle, language changes because speakers are 'sloppy' and simplify their speech in various ways. Accordingly, abbreviated forms like math for mathematics and plane for airplane arise. Going to becomes gonna because the latter has two fewer phonemes to articulate. . . . On the morphological level, speakers use showed instead of shown as the past participle of show so that they will have one less irregular verb form to remember.