• The history of research related to the role of the L1 in SLA is varied and filled with controversies that come with the changing and developing approaches to the field.
• One ever-evolving theory is interlanguage, which was a term coined by Larry Selinker (as cited by Lightbown & Spada, 2013, p. 43) to describe a learner’s developing second language knowledge.

Lightbown and Spada (2013, p. 43) describe how interlanguage is constructed and influenced by languages that have been previously learned, as well as by the current language being learned. These authors also note that interlanguage is dynamic, ever-evolving, and based on responses gained as the learner tests their hypothesis of the second language (Lightbown & Spada, 2013, p. 43).

Along with interlanguage, the Transfer theory also details the role of the L1 in the SLA.

• The transfer theory was developed by Lado (as cited by Gass, 1984).
• Sought to explain the L1's role in SLA by hypothesizing that a person’s L1 could influence their developing L2 through the transference of elements from their L1 to the construction of the L2 (p. 115).

Not the only force:

Gass (1984) also adds that during the development of the theory, it became apparent that while there are instances where the transfer occurs, transfer was not the only force determining the construction of a L2 (p 116).

The theories of interlanguage and transfer are important in this discussion for two reasons:

1. Romero and Manjarres (2017) state, a learner’s L1 is the first source of language comprehension that language learners have, and they resort to making connections to the L2 using their L1 schemas (p. 123).
2. UG plays an important role during SLA. In addition, UG plays a role in transference and interlanguage.
3. Cummins illustrates very well the importance of the L1 in SLA and why it needs to be taken into consideration when designing instruction. Cummins (2007) states that: