The document discusses different theories on the development of syntactic structures in first and second language acquisition: 1. The document outlines Radford's theory that L1 acquisition begins with a bare verb phrase (VP) projection and functional projections like IP develop later in identifiable stages. 2. It also discusses Clashen's view that functional projections develop one-by-one through successive applications of X-Theory. 3. The document then applies these theories of L1 acquisition to L2 acquisition, suggesting that L2 learners build up phrase structures gradually in the same staged manner, first transferring properties of their L1 VP like headedness before developing functional projections.