Discrimination of /ra/–/la/ speech continuum by native speakers of English under nonisolated conditions

The discrimination of an /r/–/l/ speech continuum presented in an isolated monosyllabic context has been studied by a number of researchers. However, when one considers normal listening environments, it is unusual for people to hear syllables in isolation. In the present research, we investigated whether the characteristics of the discrimination performance for a /ra/–/la/ continuum presented under the isolated condition are also observed when the continuum is presented under nonisolated conditions, or more ordinary listening conditions. Two nonisolated conditions were employed: 1) the continuum was presented within a sentence, and 2) the continuum was preceded and followed by pure tones. Experiments revealed that the discrimination performance under condition 2) was similar to that under the isolated condition; however, the performance under condition 1) was different from those under the other conditions. The research suggests that the characteristics of the discrimination performance under nonisolated conditions are not necessarily identical to those under the isolated condition.