Most of the mistakes which second language learners make are due to interference from their first language. Teachers should present grammatical rules one at a time, and learners should practice examples of each one before going on to another. Teachers should teach simple language structures before complex ones. Learners' errors should be corrected as soon as they are made in order to prevent the formation of bad habits. Teachers should use materials that expose students only to those language structures which have already been taught.
Students learn what they are taught.
The authors' argument is corroborated by evidence - a series of case studies illustrating the phenomena under scrutiny. These are truly convincing. Their focus on only these theories has been justified on the grounds that they represent views which are based on the assumption that first and second language learning are identical. The third chapter neatly deals with the ways in which intelligence, aptitude, personality, and motivational characteristics, learning styles, and age can impact on second language learning. Yet, they assert that 'in a classroom, a sensitive teacher, who takes learners' individual personalities and learning styles into account can create a learning environment in which all learners can be successful in learning a second language'.