High variability phonetic training facilitates categorical perception of Mandarin lexical tones in L2 older adults: A link to auditory processing

The current study investigated the facilitatory effects of High Variability Phonetic Training (HVPT) in second language (L2) categorical perception (CP) of Mandarin lexical tones. It also explored whether and how individual differences in auditory processing predicted gains from such training. The participants were 32 native English-speaking adults aged over 60 years who were learning Mandarin Chinese as their L2. They were randomly divided into the HVPT group (HG) (n = 16) and the control group (CG) (n = 16). Their L2 CP performance was assessed through an identification task and discrimination task before training, immediately after training, and two months later. Auditory processing tests were also conducted to measure the participants' ability to encode spectral and temporal details of sounds. Linear mixed-effects (LME) models showed that, compared to the CG, the HG exhibited a more pronounced improvement in tonal categorization. Furthermore, regression analysis confirmed that individual differences in perceptual acuity significantly predicted gains from training in L2 CP of Mandarin lexical tones.