This paper tests the Full Transfer Full Access Hypothesis (FTFA) (Schwartz and Sprouse 1996), investigating the L2 acquisition of a semantic parameter that is set to one value in English and another in Turkish. The relevant structure is quantificational scope: the two languages are in a subset-superset relationship with respect to the scopal interpretations they allow for sentences that involve both negation and numeral quantifiers, such as Donald didn't find two guys, with Turkish being the subset and English being the superset language. The former allows only surface scope interpretations (as in child English; see, e.g., Lidz and Musolino 2002 for child English facts) whereas the latter allows inverse scope interpretations, too. Therefore, given L1s and L2s like English and Turkish, in accordance with the FTFA, it is hypothesized that there will be directional differences in eventual success in acquiring L2 scope facts. The results of a Truth Value Judgment Task show that this hypothesis is borne out: L1 Turkish learners of L2 English can acquire the additional interpretation on the basis of positive evidence and behave like native English speakers. L1 English learners of L2 Turkish, on the other hand, are unable to lose this interpretation, for there is no positive evidence to show that the relevant interpretation is disallowed in Turkish. Therefore, their grammar diverges from that of the target language, though it is still one that is constrained by UG. In conclusion, both UG and L1 grammar influence the status of interlanguage grammars, and English speaking Turkish L2ers face a learnability problem, one that is avoided by children.