SUMMARY
This descriptive non-experimental quantitative study investigated if the pronunciation of the –ed morphemeim proves as the English proficiency level develops. A random sampling design was used to recruit research participants. A target sample of 48 Nicaraguan English as a foreign language students were chosen from an accessible population (N= 91) to participate in this research. The participants’ age ranged from 18 to 24, with a mean age of 21 years. They belonged to three English proficiency levels: high beginners, intermediate, and high intermediate. Findings showed that more advanced English as a Foreign Language learners had a significantly higher pronunciation accuracy on the production of the allomorphs, /t/ and /d/. Their error rate on these two allomorphs was as low as 9% and 8%, respectively. Concerning the /?d, ?d/ allomorph, no significant differences were found among proficiency levels. These results were interpreted in view of the Markedness Differential Hypothesis (Eckman, 1977) and the Similarity Differential Rate Hypothesis (Major & Kim, 1996). The trends in the data definitely suggested support for the Similarity Differential Rate Hypothesis which postulates that markedness by itself cannot explain the development of L2 learners as they improve their L2 proficiency level. This study offers implications for the teaching of the three phonological realizations of the -ed past tense inflection.