Children’s early word production is influenced by the statistical frequency of speech sounds and combinations. Three experiments asked whether this production effect can be explained by a perceptual learning mechanism that is sensitive to word-token frequency and/or variability. Four-year-olds were exposed to nonwords that were either frequent (presented 10 times) or infrequent (presented once). When the frequent nonwords were spoken by the same talker, children showed no significant effect of perceptual frequency on production. When the frequent nonwords were spoken by different talkers, children produced them with fewer errors and shorter latencies. The results implicate token variability in perceptual learning.

Phonotactics -the permissibility of sound sequences within a word -correspond to lexical statistics, but controversy persists over which statistics are being tracked. In this study, lexical type and token counts were compared as they contributed to phonotactic extraction from an artificial lexicon. Young-adult participants were familiarized with a set of CVCCVC nonwords contextualized as a lexicon of Martian animal names. The type and token frequencies of word-medial consonant sequences within those names were varied systematically. Participants then rated new nonwords, containing the same medial sequences, on a 7-point scale for similarity to the Martian animal names. Higher ratings only followed high type frequency familiarization conditions, suggesting that word-types drove phonotactic extraction. Additionally, participants reversed the typical preference for highfrequency English sequences, likely because they rated nonwords according to their membership in an unknown language. This finding suggests cognitively separable tracking of artificial language statistics and preexisting representations.

The experiments here build on the widely reported finding that children are most accurate when producing phonotactic sequences with high ambient-language frequency. What remains controversial is a description of the input that children must be tracking for this effect to arise. We present a series of experiments that compare two ambient-language properties, token and type frequency, as they contribute to phonotactic learning. Token frequency is the raw number of exposures children have to a particular pattern; type frequency refers to a count of abstract entities, such as unique words. Our results suggest that children's production accuracy is most sensitive to a combination of type and token frequency: children were able to generalize a target phonotactic sequence to a new word when familiarized with multiple word-types across tokens from multiple talkers, but not when presented with either word-types with no talker variability or multiple talker-tokens of a single word.

What cognitive mechanisms account for the trajectory of speech sound development, in particular, gradually increasing accuracy during childhood? An intriguing potential contributor is statistical learning, a type of learning that has been studied frequently in infant perception but less often in child speech production. To assess the relevance of statistical learning to developing speech accuracy, we carried out a statistical learning experiment with four- and five-year-olds in which statistical learning was examined over one week. Children were familiarized with and tested on word-medial consonant sequences in novel words. There was only modest evidence for statistical learning, primarily in the first few productions of the first session. This initial learning effect nevertheless aligns with previous statistical learning research. Furthermore, the overall learning effect was similar to an estimate of weekly accuracy growth based on normative studies. The results implicate other important factors in speech sound development, particularly learning via production.

Purpose Frequent sounds and frequent words are both acquired at an earlier age and are produced by children more accurately. Recent research suggests that frequency is not always a facilitative concept, however. Interactions between input frequency in perception and practice frequency in production may limit or inhibit growth. In this study, we consider how a range of input frequencies affect production accuracy and referent identification. Method Thirty-three typically developing 3- and 4-year-olds participated in a novel word-learning task. In the initial test block, participants heard nonwords 1, 3, 6, or 10 times—produced either by a single talker or by multiple talkers—and then produced them immediately. In a posttest, participants heard all nonwords just once and then produced them. Referent identification was probed in between the test and posttest. Results Production accuracy was most clearly facilitated by an input frequency of 3 during the test block. Input frequency interacted with production practice, and the facilitative effect of input frequency did not carry over to the posttest. Talker variability did not affect accuracy, regardless of input frequency. The referent identification results did not favor talker variability or a particular input frequency value, but participants were able to learn the words at better than chance levels. Conclusions The results confirm that the input can be facilitative, but input frequency and production practice interact in ways that limit input-based learning, and more input is not always better. Future research on this interaction may allow clinicians to optimize various types of frequency commonly used during therapy.