This is basically perceptual categorization. To understand this process better, it would be nice to know about the formation of complex auditory categories. Unfortunately, much of the categorization work has concentrated on the visual mode using categories that are quite different from those of speech sounds. We are using nonspeech sounds that mimic some of the complexity of speech sounds to train people on new categories. This work has important implications for theoretical approaches to infant language acquistion and for practical approaches to second language learning.
Empirical work is certainly important.
However, it is difficult to integrate the results without theory. Speech communication used to be a very theoretical field but it has become much more practical under the influence of engineering approaches. The field has lost much of its poetry. We consider discussion at a theoretical level to be as important as basic research and the two must interact for progress. Whereas others may dismiss theoretical debate as useless, we welcome it.