Using an articulatory model we show that locus equations make special use of the phonetic space of possible locus patterns. There is nothing articulatorily inevitable about their linearity or slope- intercept characteristics. Nonetheless, articulatory factors do play an important role in the origin of simulated locus equations, but they cannot, by themselves, provide complete explanations for the observed facts. As in other domains, there is interaction between perceptual and motor factors.

The frame/content theory justifiably makes tinkering an important explanatory principle. However, tinkering is linked to the accidental and, if completely decoupled from functional constraints, it could potentially play the role of an “idiosyncracy generator,” thus offering a sort of “evolutionary” alibi for the Chomskyan paradigm – the approach to language that MacNeilage most emphatically rejects. To block that line of reasoning, it should be made clear that evolutionary opportunism always operates within the constraints of selection.

Chemistry, genetics, physics, and linguistics all present instances of reuse. I use the example of how behavioral constraints may have contributed to the emergence of phonemic reuse. Arising from specific facts about speech production, perception, and learning, such constraints suggest that combinatorial reuse is domain-specific. This implies that it would be more prudent to view instances of neural reuse not as reflecting a but as a fortuitous set of converging phenomena.