Whether or not he is familiar with the technical terms currently favored, or aware of the actual processes behind these terms, a speaker or student of Spanish, on some undefined level of consciousness, senses (or acts as if he sensed) the existence of such contrastable inflectional models as sent-ir ‘to feel’ : sient-e ‘(he, she, it) feels’ vs. ped-ir ‘to ask’ : pid-e ‘(he, she, it) asks’. The native speaker may even at some time or other have faced the dilemma of choosing, in the stressed syllable of such a verb form, between ie and i, and the foreign student is certain to have come to grips with such practical difficulties and to have been guilty, upon occasion, of gross errors. Preceptive grammarians and practitioners of language teaching, accordingly, have at all times paid attention to the hazards of the choice between the two conjugational categories.