Flexibility and stability of speech sounds: The time course of lexically-driven recalibration

Perceptual stability is obviously advantageous, but being able to adjust to the prevailing environment is also adaptive. Previous research has identified ways in which the categorization of speech sounds shifts as a function of recently heard speech. Dozens of studies have examined “lexically driven recalibration”, an adjustment to categorization after listeners hear a number of words with a particular speech sound designed to be perceptually ambiguous. Despite the large number of these studies, little is known about how long the adjustment endures. Using two different stimulus sets, we assess the recovery time after lexically driven recalibration. In addition, we examine whether the size of the recalibration effect diminishes during the identification test used to measure it, and whether the recalibration effect is stronger for one side of a tested contrast or the other. The effect did in fact decline during its measurement, and one side of the contrast (/s/) produced stronger shifts than others (/ʃ/ or /θ/) under the conditions typically examined in recalibration studies. Recalibration was quite robust after 24 hours for both stimulus sets, and still measurable after one week for one of them. This time course is strikingly different than the recovery times reported in previous studies for two other adjustment processes – selective adaptation and audiovisually driven recalibration. The vastly different time courses pose a major challenge for models that ascribe these phenomena to the same adjustment function. Thus, such models will need to be substantially modified, or alternative models will need to be developed.