Based on a neurobiological perspective, the authors of this work address the effects of the mother tongue on learning a second language. Although studies on the problem have been conducted in a number of countries, few deal with a neurobiological approach, and much less when it comes to Spanish as the first language. A compilation of descriptive and experimental literature was developed to acquire the data necessary to accomplish the objectives of the study, and a qualitative meta-analysis of the data obtained as such was performed using correlation tables. The data indicate that acquiring a second language will be influenced invariably by the pre-established schemes of the first language and there are neurobiological aspects underlying certain mechanisms involving interference and the acquisition of a second language. It also was found that the more similar the languages, the more the underlying neural mechanisms facilitate the transfer from one to another.