Because they said so:

This book reports the findings of an investigation that employed life history to understand the different factors that influenced the motivations to learn English and perceptions about this language among four English learners. These first-year students were purposely selected to include Puerto Rican students from both public and private educational settings, also including a return migrant and a foreign student. Life histories were collected through a series of interview protocols and a focus group. Parents and teachers were found to be the greatest influence in these students language acquisition. Participants however, reported that teachers were mostly responsible for the amount of English they had learned.

Autorentext
The author is pursuing a doctoral degree at the University of Arizona under the Language, Reading and Culture program. She has Master s Degree in English Education from the University of Puerto Rico, Mayagüez. Her research and teaching foci are geared toward English learners, especially in the Puerto Rican context.