This commentary focuses on the claim that perceptual demands have caused the linearity exhibited by locus equations. I discuss results of an experiment demonstrating that, contrary to Sussman et al.'s claims, locus equations do not have relevance for the perception of stop consonants. I therefore argue against the plausibility of the orderly output constraint.

The present description of the Merge model addresses only auditory, not audiovisual, speech perception. However, recent findings in the audiovisual domain are relevant to the model. We outline a test that we are conducting of the adequacy of Merge, modified to accept visual information about articulation.