Interfaces, frequency, and the primary linguistic data problem

Interfaces are defined biological relations, like the link between heart and lung, while interactions describe non-designed but inevitable biological consequences of being a mechanism with a single source of energy. A careful look at the representations needed a careful look that each mental module has a separate form of representation. And therefore interfaces require careful matching. Merge and labeling describe a hierarchy in language but perhaps not other mental hierarchies. It is distinct from Concatenation, which may be a broader mental capacity; Language calls for recursive Merge and Label hierarchies.We argue that frequency is not a meaningful concept in psychology without a representation whose frequency is being tabulated. Therefore every model of change must work with representations. However it is possible for representations that are not perfectly captured by grammar to be identified. For instance, the notion of leftward focal stress can apply at the word, phrase, or morphological level at first before being linked to separate modules in the mature grammar. Lebeaux's notion of Adjoin-Alpha as an acquisition primitive is thereby supported. In sum, it is possible that frequency-linked representations, still connected to an innate UG, play a role in acquisition. We conclude with an analysis of gradual −ed acquisition that re-introduces a role for LAD.