This article develops a new approach to specificity effects based on comparing differential object marking (DOM) in Turkish with a novel DOM paradigm observed in Uyghur. On this basis, I argue that specificity does not always correlate with VP-externality (e.g., Diesing 1992); rather, it correlates with whether the object has moved to a particular structural position. Further, I show that the variation observed between the two DOM paradigms can be captured as a result of a difference in the languages’ middle-field phase boundaries. Several additional contrasts between the two languages are traced back to this difference in phase boundaries, which is also situated within a broader pattern of typological variation.