Noam Chomsky defined UG as, “.. a sort of template, containing the principles that are universal to all human languages” (Lightbown & Spada, 2013, p. 20).
According to Gass (2013), the UG theory holds that there are mental universal principles that govern language and its meaning (p. 161). Gass (2013) continues by stating that at the heart of this theory is the concept that all languages have a core set of grammar rules created by abstract principles and varying language parameters (p. 161). Under the UG approach, Gass (2013) states that in first language (L1) acquisition there exists:
. . . [an] innate language facility that limits the extent to which languages can vary. That is, it specifies the limits of a possible language. The task for learning is greatly reduced if one is equipped with an innate mechanism that constrains possible grammar formation (p. 161).
In relation to SLA, the UG approach focuses on the question of the individual's ability access to UG “template” (Gass, 2013, p. 163). Hypothesis connected to how individuals access UG include Fundamental Difference Hypothesis (FDH) and Access to UG Hypothesis. Each of these hypotheses address how a language learner might access UG “template” while they are learning an L2.
FDH states that language acquisition for a child is different than that of an adult, because unlike children, adult L2 learners have knowledge of a full linguistic system (Gass, 2013, p. 164). According to Gass, FDH takes UG into consideration but also views UG as only being accessible through the L1 and is therefore not available to older L2 learners. Learners instead then use their knowledge of their L1 to construct a pseudo-UG (Gass, 2013, p. 165). If UG is operative only through the L1, as suggested by FDH, then the expectation would be that only L1 features would develop in the L2 (Gass, 2013, p. 171).
According to Gass (2013), access to UG Hypothesis is an opposing view to the FDH. Instead of viewing UG as only accessible in the L1, it instead considers it to be separate and unchanged from an L1 acquisition. UG then plays a role in the L2 learner’s interlanguage grammar (Grass, 2013, p. 165). White (as cited in Gass, 2013) states that the initial state of L2 learning takes either the L1 or the UG as the start. There are several different hypotheses that present arguments for the roles of the L1 and UG in L2 acquisition. The first two hypotheses discussed view L1 as being the base for SLA. The full transfer/full access hypothesis argues that a learner starts with their L1 grammar and retains it as a base, but during acquisition, they have access to the UG when the L1 is insufficient.