Effectiveness of artificial intelligence tools in the development of English language vocabulary: a study with seventh grade students of Basic General Education

Abstract

Vocabulary is one of the cornerstones of learning English as a foreign language, and today artificial intelligence (AI) tools are opening new possibilities for strengthening it in the classroom. This study sought to determine the extent to which the use of AI tools contributes to the development of English vocabulary in seventh-grade students. A mixed-methods approach with a sequential explanatory design was used: the quantitative phase followed a single-group pre-experimental design, with measurements taken before and after the intervention, and involved 27 students between 11 and 12 years old. The intervention lasted eight weeks, with two 40-minute sessions per week using Duolingo. Vocabulary was measured with a 20-item test, and the data were analyzed using the paired-samples t-test and Cohen's d effect size. The results showed a clear increase: the mean score rose from 10.30 points in the pretest to 13.22 in the posttest, with a statistically significant difference, t (26) = 7.68. p < 0.001, and a large effect size ( d = 1.48). From a qualitative perspective, motivation, consistent practice, immediate feedback, and teacher support emerged as key factors in explaining the progress achieved. Therefore, integrating AI tools in a pedagogically planned manner has real potential to strengthen English vocabulary, especially when used as supplementary support within a well-structured teaching process.