A widely held belief is that speech perception and speech production are tightly linked, with each modality available to help with learning in the other modality. This positive relationship is often summarized as perception and production being \"two sides of the same coin.\" There are, indeed, many situations that have shown this mutually supportive relationship. However, there is a growing body of research showing very different results, with the modalities operating independently, or even in opposition to each other. We review the now-sizeable literature demonstrating the negative effect that speech production can have on perceptual learning of speech, at multiple levels (particularly at the lexical and sublexical levels). By comparing the situations that show this pattern with ones in which more positive interactions occur, we provide an initial account of why the different outcomes are found, identifying factors that lead to either positive or negative effects of production on perception. The review clarifies the complex relationship that exists between the two modalities: They are indeed linked, but their relationship is more complicated than is suggested by the notion that they are two sides of the same coin.

UNASSIGNED: Current evidence shows that children with developmental language disorder (DLD) benefit from spaced retrieval during word learning activities. Word recall is quite good relative to recall with alternative word learning procedures. However, recall on an absolute basis can be improved further; many studies report that fewer than two-thirds of the words are learned, even with the assistance of spaced retrieval during the learning activities. In this article we identify details of spaced retrieval that are less well understood in an effort to promote more effective learning through retrieval practice.
UNASSIGNED: We discuss the importance of factors such as: (a) integrating immediate retrieval with spaced retrieval trials; (b) determining whether gradual increases in spacing have more than short-term benefits relative to equal spacing; (c) discovering the number of successful retrievals sufficient to ensure later recall; (d) using spaced retrieval to avoid erosion of phonetic details on later recall tests; and (e) whether the well-documented difficulties with learning word forms might be tied to a particular subgroup of children with DLD. We also speculate on some of the possible reasons why spaced retrieval is beneficial in the first place.
UNASSIGNED: Although many children with DLD make gains in word learning through procedures that incorporate spaced retrieval, there are numerous details involved in the process that can alter its success. Until we have a better understanding of the boundaries of spaced retrieval\'s effectiveness, we will not be taking full advantage of this promising addition to word learning procedures.
UNASSIGNED: Spaced retrieval activities can be an important addition to the resources that clinicians and educators have available to assist children in their word learning. With a deeper understanding of the issues discussed here, we should be able to put spaced retrieval to even greater use.

UNASSIGNED: Many children who are deaf and hard of hearing (DHH) show poorer auditory word-learning skills than children with typical hearing (TH). The goal of this study was to test the effect of retrieval practice on word learning in children who are hard of hearing (HH).
UNASSIGNED: Twenty-six TH children and 16 children who are HH completed a speech perception and a vocabulary test, and a rapid word-learning game to learn new words under no retrieval, immediate retrieval, and spaced retrieval conditions.
UNASSIGNED: Linear mixed-effect models revealed that learning condition and time predicted 48% of the variance in word recognition, and age predicted 15% of word recall variance. We observed no differences in word recognition and recall between TH children and children who are HH. Children learned and remembered more words in the immediate and spaced retrieval practice conditions than in the no retrieval condition.
UNASSIGNED: Retrieval practice is more effective for word learning and retention than passive exposure (no retrieval). Clinical and educational practices for children who are DHH could combine explicit instruction using targeted exposures and retrieval of new words with naturalistic approaches. Future studies should assess retrieval practice in real-life interventions to inform clinical and educational practices.

The word-frequency distributions children hear during language learning are highly skewed (Zipfian). Previous studies suggest that such skewed environments confer a learnability advantage in tasks that require the learner to discover the units that have to be learned, as in word-segmentation or cross-situational learning. This facilitative effect has been attributed to contextual facilitation from high frequency items in learning lower frequency items, and to better learning under the increased predictability (lower entropy) of skewed distributions. Here, we ask whether Zipfian distributions facilitate learning beyond the discovery of units, as expected under the predictability account. We tested children\'s learning of novel word-referent mappings in a learning task where each mapping was presented in isolation during training, and did not need to be dicovered. We compared learning in a uniform environment to two skewed environments with different entropy levels. Children\'s learning was overall better in the two skewed environments, even for low frequency items. These results extend the facilitative effect of Zipfian distributions to additional learning tasks and show they can facilitate language learning beyond the discovery of units.

Accurately capturing children\'s word learning abilities is critical for advancing our understanding of language development. Researchers have demonstrated that utilizing more complex statistical methods, such as mixed-effects regression and hierarchical linear modeling, can lead to a more complete understanding of the variability observed within children\'s word learning abilities. In the current paper, we demonstrate how a person-centered approach to data analysis can provide additional insights into the heterogeneity of word learning ability among children while also aiding researchers\' efforts to draw individual-level conclusions. Using previously published data with 32 typically developing and 32 late-talking infants who completed a novel noun generalization (NNG) task to assess word learning biases (i.e., shape and material biases), we compare this person-centered method to three traditional statistical approaches: (1) a t-test against chance, (2) an analysis of variance (ANOVA), and (3) a mixed-effects regression. With each comparison, we present a novel question raised by the person-centered approach and show how results from the corresponding analyses can lead to greater nuance in our understanding of children\'s word learning capabilities. Person-centered methods, then, are shown to be valuable tools that should be added to the growing body of sophisticated statistical procedures used by modern researchers.

Objects and places are foundational spatial domains represented in human symbolic expressions, like drawings, which show a prioritization of depicting small-scale object-shape information over the large-scale navigable place information in which objects are situated. Is there a similar object-over-place bias in language? Across six experiments, adults and 3- to 4-year-old children were asked either to extend a novel noun in a labeling phrase, to extend a novel noun in a prepositional phrase, or to simply match pictures. To dissociate specific object and place information from more general figure and ground information, participants either saw scenes with both place information (a room) and object information (a block in the room), or scenes with two kinds of object information that matched the figure-ground relations of the room and block by presenting an open container with a smaller block inside. While adults showed a specific object-over-place bias in both extending novel noun labels and matching, they did not show this bias in extending novel nouns following prepositions. Young children showed this bias in extending novel noun labels only. Spatial domains may thus confer specific and foundational biases for word learning that may change through development in a way that is similar to that of other word-learning biases about objects, like the shape bias. These results expand the symbolic scope of prior studies on object biases in drawing to object biases in language, and they expand the spatial domains of prior studies characterizing the language of objects and places.

Vowelless words are exceptionally typologically rare, though they are found in some languages, such as Tashlhiyt (e.g., fkt \'give it\'). The current study tests whether lexicons containing tri-segmental (CCC) vowelless words are more difficult to acquire than lexicons not containing vowelless words by adult English speakers from brief auditory exposure. The role of acoustic-phonetic form on learning these typologically rare word forms is also explored: In Experiment 1, participants were trained on words produced in either only Clear speech or Casual speech productions of words; Experiment 2 trained participants on lexical items produced in both speech styles. Listeners were able to learn both vowelless and voweled lexicons equally well when speaking style was consistent for participants, but learning was lower for vowelless lexicons when training consisted of variable acoustic-phonetic forms. In both experiments, responses to a post-training wordlikeness ratings task containing novel items revealed that exposure to a vowelless lexicon leads participants to accept new vowelless words as acceptable lexical forms. These results demonstrate that one of the typologically rarest types of lexical forms - words without vowels - can be rapidly acquired by naive adult listeners. Yet, acoustic-phonetic variation modulates learning.

The majority of the new words that we learn every day as adults are morphologically complex; yet, we do not know much about the role of morphology in novel word learning. In this study, we tackle this issue by comparing the learning of: (i) suffixed novel words (e.g. flibness); (ii) novel words that end in non-morphological, but frequent letter chunks (e.g. fliban); and (iii) novel words with non-morphological, low-frequency endings (e.g. flibov). Words are learned incidentally through sentence reading, while the participants\' eye movements are monitored. We show that morphology has a facilitatory role compared with the other two types of novel words, both during learning and in a post-learning recognition memory task. We also showed that participants attributed meaning to word parts (if flibness is a state of happiness, then flib must mean happy), but this process was not specifically triggered by the presence of a suffix (flib must also mean happy in fliban and flibov), thus suggesting that the brain tends to assume similar meanings for similar words and word parts.

Infants\' interactions with social partners are richly multimodal. Dyads respond to and coordinate their visual attention, gestures, vocalizations, speech, manual actions, and manipulations of objects. Although infants are typically described as active learners, previous experimental research has often focused on how infants learn from stimuli that is well-crafted by researchers. Recent research studying naturalistic, free-flowing interactions has explored the meaningful patterns in dyadic behavior that relate to language learning. Infants\' manual engagement and exploration of objects supports their visual attention, creates salient and diverse views of objects, and elicits labeling utterances from parents. In this chapter, we discuss how the cascade of behaviors created by infant multimodal attention plays a fundamental role in shaping their learning environment, supporting real-time word learning and predicting later vocabulary size. We draw from recent at-home and cross-cultural research to test the validity of our mechanistic pathway and discuss why hands matter so much for learning. Our goal is to convey the critical need for developmental scientists to study natural behavior and move beyond our \"tried-and-true\" paradigms, like screen-based tasks. By studying natural behavior, the role of infants\' hands in early language learning was revealed-though it was a behavior that was often uncoded, undiscussed, or not even allowed in decades of previous research. When we study infants in their natural environment, they can show us how they learn about and explore their world. Word learning is hands-on.

BACKGROUND: There is growing evidence that COVID-19 brought changes that immediately affected early language development. Little is known for how long these COVID-19 related changes shaped development. The current study systematically and longitudinally addressed this issue, following up children\'s language development throughout the first 2.5 years.
METHODS: The present study follows up on the sample from Frota et al. (2022), which demonstrated that 7-9-month-old infants born and raised during the pandemic do not segment words unlike pre-pandemic peers. Four studies were conducted: (1) word segmentation task at 12 months of age (Npandemic = 15); (2) word learning task at 20 months of age (Npandemic = 20); (3) language and communication development up to 30 months of age, via CDI and CSBS parental reports (Npandemic ranged 25-74); (4) overall development at 30 months of age using the Griffiths Developmental Scales (Npandemic = 16).
RESULTS: The pandemic sample consistently underperformed in all four studies in comparison to pre-pandemic data. There was no evidence of developed word segmentation abilities at 12 months of age, and no successful word learning at 20 months of age. Lexical development between 12 and 24 months of age was lower than in the pre-pandemic sample, while social communication did not seem to be affected. At 30 months of age, the pandemic sample showed lower scores and lower mental age on the Language and Communication Griffiths\' subscale, in comparison to the pre-pandemic data.
CONCLUSIONS: Infants born and raised during the pandemic have a poorer language development, that persists at least until 30 months of age.