Discrimination of the “tempo of frequency change” cue

The stop/glide distinction, e.g., /b/ versus /w/, is cued by the rate of spectral change in the formant transitions [Liberman et al., J. Exp. Psychol. 52, 127–137 (1956)]. A series of 12 stimuli from /be/ to /we/ were synthesized, differing only in the rate of formant frequency change. Five subjects took identification and two‐step ABX discrimination tests with these stimuli, resulting in functions typical of “categorical perception.” Other two‐step tests altered the discrimination of differences both within and across phoneme boundaries. The three‐interval forced‐choice (3IFC) or “oddity” test, which makes more demands on memory, produced generally poorer discrimination than ABX, with lower peaks at the boundary. The less demanding four‐interval paired test (4IAX) enhanced discrimination of stimulus pairs across and near the boundary, with little effect elsewhere. In another oddity test, each judgement was preceded by repeated presentations of one of the stimuli, which facilitated discrimination markedly both within and across categories. Under these conditions, the discrimination functions of some subjects are not so clearly categorical.