Abstract
Findings on the perceptual reorganization of lexical tones are mixed. Some studies report good tone discrimination abilities for all tested age groups, others report decreased or enhanced discrimination with increasing age, and still others report U-shaped developmental curves. Since prior studies have used a wide range of contrasts and experimental procedures, it is unclear how specific task requirements interact with discrimination abilities at different ages. In the present work, we tested German and Cantonese adults on their discrimination of Cantonese lexical tones, as well as German-learning infants between 6 and 18 months of age on their discrimination of two specific Cantonese tones using two different types of experimental procedures. The adult experiment showed that German native speakers can discriminate between lexical tones, but native Cantonese speakers show significantly better performance. The results from German-learning infants suggest that 6- and 18-month-olds discriminate tones, while 9-month-olds do not, supporting a U-shaped developmental curve. Furthermore, our results revealed an effect of methodology, with good discrimination performance at 6 months after habituation but not after familiarization. These results support three main conclusions. First, habituation can be a more sensitive procedure for measuring infants' discrimination than familiarization. Second, the previous finding of a U-shaped curve in the discrimination of lexical tones is further supported. Third, discrimination abilities at 18 months appear to reflect mature perceptual sensitivity to lexical tones, since German adults also discriminated the lexical tones with high accuracy.
Highlights
During the first year of life, infants’ perception abilities may change for stimuli that are not present or not relevant in their environment
Our study focuses on the latter factor and compares the effects of familiarization vs. habituation in the initial exposure phase on German-learning infants’ discrimination of a Cantonese tone contrast
Statistical analyses were run on the number of correct responses as the dependent variable. The performance of both language groups was significantly higher than predicted by chance for all tone contrasts
Summary
During the first year of life, infants’ perception abilities may change for stimuli that are not present or not relevant in their environment. Previous research on lexical tone discrimination in infants is characterized by a rather complex pattern of findings: prior studies have found evidence for an increase, a decrease, and no-change in infants’ and toddlers’ ability to discriminate non-native tone contrasts across ages (for an overview, see Table 1). These divergent findings may be related to a number of dimensions on which these studies varied, including the tone contrasts used, the native language of the participants, and the experimental procedures. The latter type of preexposure may be more sensitive to the performance of individual infants
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