This document discusses several factors that influence differences in how individuals acquire a second language: 1. Age - Younger learners more easily acquire native-like grammar intuitions through informal learning, while older learners learn faster due to better memory and analytical abilities and are more successful in formal learning settings. 2. Sex - Women generally excel at verbal fluency, memorization, and interpretation, while men's brains are better organized for speech and they perform better with automatized and rule-based skills. 3. Aptitude - Language learning aptitude encompasses abilities like sound processing, pattern recognition, memory capacity, and rule application that contribute to an individual's talent for acquiring a new language.