The Role of Lexical Status and Individual Differences for Perceptual Learning in Younger and Older Adults

Abstract

Perceptual learning in younger and older adults 2 Abstract Purpose: This study examined whether older adults remain perceptually flexible when presented with ambiguities in speech in the absence of lexically disambiguating information. We expected older adults to show less perceptual learning when top-down information was not available. We also investigated whether individual differences in executive function predicted perceptual learning in older and younger adults.Method: Younger (n=31) and older adults (n=27) completed two perceptual learning tasks comprised of a pretest, exposure, and posttest phase. Both learning tasks exposed participants to clear and ambiguous speech tokens, but crucially, the lexically-guided learning task provided disambiguating lexical information, while the distributional learning task did not. Participants also performed several cognitive tasks to investigate individual differences in working memory, vocabulary, and attention-switching control. Results:We found that perceptual learning is maintained in older adults, but that learning may be stronger in contexts where top-down information is available. Receptive vocabulary scores predicted learning across both age groups and in both learning tasks.Conclusions: Implicit learning is maintained with age across different learning conditions, but remains stronger when lexically biasing information is available. We find that receptive vocabulary is relevant for learning in both types of learning tasks, suggesting the importance of vocabulary knowledge for adapting to ambiguities in speech.Perceptual learning in younger and older adults 3

The Neural Correlates Underlying Lexically-Guided Perceptual Learning

“…Previous studies have shown that listeners show different degrees of lexically-guided perceptual learning [12] [17], which was also demonstrated in our behavioral results. To investigate whether the observed change in amplitude between pretest and posttest reflected lexically-guided perceptual learning, the size of the ERP effect was correlated by subjects with the degree of learning observed in the behavioral task.…”

“…It has been argued that focusing listeners' attention on the ambiguity of a sound will inhibit this type of learning [9] [19]. However, despite employing a phonetic categorization task at pretest and posttest which focused participants' attention on the ambiguous nature of the sound stimuli, we observed a clear lexically-guided perceptual learning effect, similar to [7] [17], in about half of our participants. These results show that lexically-guided perceptual learning can take place under conditions where ambiguity is made explicit to the listener.…”

“…Here, we use a different set-up, wherein we investigate lexically-guided perceptual learning using a pretest-posttest design [7] [17]. This allows us to use only one biasing context (the /f/ context in our case), which reduces the number of people that need to be tested by half.…”

Individual Differences in Distributional Learning for Speech: What's Ideal for Ideal Observers?

“…Sensitivity to distributional variation in the input does not cease after the infant has acquired the phonetic inventory of a language (Clayards, Tanenhaus, Aslin, & Jacobs, 2008;Theodore & Monto, 2019). Instead, functional plasticity is observed across the life span such that listeners dynamically modify the mapping to speech sounds in line with statistical distributions of acoustic-phonetic cues in the input (e.g., Colby, Clayards, & Baum, 2018;Norris, McQueen, & Cutler, 2003;Theodore & Monto, 2019).…”

“…Relatively less is known about factors that influence individual differences in distributional learning for the earliest stages of language comprehension, including the stage in which listeners map speech acoustics to consonants and vowels. Colby et al (2018) recently examined whether individual differences in receptive vocabulary, working memory, 1…”