Perceptual equivalence of two acoustic cues for stop-consonant manner

The first experiment examined the effects of orthogonal variation in two acoustic cues that are both produced by the articulation of a stop consonant. One component of the articulation produces a temporal cue, the other a spectral cue. In a phonetic identification task, these quite different cues were found to engage in a trading relation: One cue could, within limits, substitute for the other. In a second experiment, the perceptual equivalence implied by that trading relation was put to a stricter test. If the cues are truly equivalent in perception, then they should have their effects on the same perceptual dimension. That being so, it should be possible to combine them in such a way that, working at cross purposes in the perceptual domain, they effectively cancel each other. Pairs of patterns so produced should, then, be harder to discriminate than pairs produced by either cue alone, and still harder than those produced when the (same) two cues are combined in the opposite way and so cooperate. That expectation was confirmed. We suggest that the equivalence thus demonstrated comes about because the two cues are processed by a system specialized to take account of their common origin in speech production. So interpreted, the equivalence may be viewed as an instance of distinctively phonetic perception.