THIS PAPER WRITTEN IN FRENCH, PRESENTS A HYPOTHESIS CONCERNING THE DECODING OF SPEECH IN SECOND LANGUAGE LEARNING. THE THEORETICAL BACKGROUND OF THE DISCUSSION CONSISTS OF WIDELY ACCEPTED LINGUISTIC CONCEPTS SUCH AS THE PHONEME, DISTINCTIVE FEATURES, NEUTRALIZATION, LINGUISTIC LEVELS, FORM AND SUBSTANCE, EXPRESSION AND CONTENT, SOUNDS, PHONEMES, MORPHEMES, LEXEMES, SEMEMES, AND ALSO THE MONEME. IDENTIFICATION, OR DECODING, PROCEEDS BY SUCCESSIVE ELIMINATIONS--PHONEMES BEING IDENTIFIED BY ELIMINATION BEGINNING WITH THE MOST IMPORTANT FEATURES. AT ALL LEVELS, CONTEXT MODIFIES THE ORDER OF ELIMINATION BY LIMITING POSSIBILITIES OF OCCURRENCE OF UNITS, AND EVEN NATIVE SPEAKERS MAKE ERRORS IN DISCRIMINATION WHEN DEPRIVED OF CONTEXT. FOR THE FOREIGN LISTENER, THE DECODING PROCESS USED IS THAT OF HIS NATIVE LANGUAGE. THE CONDITIONS OF TEACHING ARE SUCH THAT HE HAS NEITHER THE SAME LINEARITY NOR THE SAME LEVELS OF CONSCIOUSNESS AS THE NATIVE SPEAKER. THIS RESEARCH REPORT IS ONE OF SEVERAL WHICH HAVE BEEN SUBMITTED TO THE OFFICE OF EDUCATION AS "STUDIES IN LANGUAGE AND LANGUAGE BEHAVIOR, PROGRESS REPORT V," SEPTEMBER 1, 1967. AN ABRIDGED VERSION OF THIS ARTICLE, UNDER THE TITLE "DISCRIMINATION AUDITIVE ET APPRENTISSAGE DES LANGUES," WILL APPEAR IN "PROCEEDINGS OF THE CONFERENCE ON LANGUAGE AND LANGUAGE BEHAVIOR," E. M. ZALE, EDITOR, NEW YORK, APPLETON-CENTURY-CROFTS. (FB)