Bedding down new words: Sleep promotes the emergence of lexical competition in visual word recognition

To sleep or not to sleep? No effect of sleep on contextual word learning in younger adults

This study investigated the effect of sleep on novel word learning through reading context. Seventy-four healthy young adults attended two testing sessions, with either overnight sleep (sleep group) or daytime wakefulness (wake group) occurring between the sessions. At the initial learning session, participants identified the hidden meanings of novel words embedded within sentence contexts and were subsequently tested on their recognition of the novel word meanings. A recognition test was also conducted at the delayed session. The analyses revealed comparable recognition of novel word meanings for the sleep and wake group at both the initial and the delayed session, indicating that there was no benefit of sleep compared with wakefulness for novel word learning through context. Overall, this study highlights the critical influence of encoding method on sleep-dependent learning, where not all forms of word learning appear to benefit from sleep for consolidation.

Sleep-dependent consolidation effects on foreign language word acquisition in a virtual reality environment

Sleep-dependent consolidation is important for novel word learning, but previous studies have neglected the potential modulating role of learning environments. The present study examines sleep-dependent consolidation effects by comparing learning in a virtual reality (VR) environment and in a traditional picture-word (PW) environment. Two groups of Chinese-English bilinguals were randomly assigned to a VR or PW environment. In both learning environments, they learned novel words in Korean, a language with which they had no prior experience. All participants learned one set of novel words on Day 1 and another set on Day 2. An explicit recognition task and an implicit primed lexical-decision task were employed to measure sleep-dependent consolidation effects from the two environments. Results revealed sleep-dependent consolidation effects in both explicit and implicit measures, but only the primed lexical-decision task showed an influence of learning environment, suggesting that novel words learned via VR had better consolidation. Taken together, our findings suggest that a VR environment that fosters a rich sensory experience facilitates sleep-dependent consolidation effects. We argue that these results provide new evidence and implications for the complementary learning system (CLS) model.

The effect of sleep and semantic information on associative novel word learning

This study investigated the effect of overnight sleep on associative novel word learning and examined whether the effects of sleep on word learning are modulated by the provision of semantic information. Seventy-five healthy young adults attended an initial word-learning session followed by a delayed testing session. An interval of overnight sleep (sleep group) or daytime wakefulness (wake group) separated the two sessions. At the initial learning session, participants learned three-word names of 20 novel objects, where half the names comprised a novel word and two semantic attributes (semantic condition), and half comprised a novel word and two meaningless proper names (name condition). Novel word cued-recall was measured at both the initial and the delayed session. Although both groups demonstrated similar cued-recall accuracy at the first session, by the delayed session the sleep group demonstrated superior cued-recall accuracy compared to the wake group. There was no influence of semantics on the sleep-dependent consolidation of the novel words. Overall, these findings suggest that novel words encoded with or without the provision of semantic information can benefit from an overnight sleep period for consolidation.

Is word learning capacity restored after a daytime nap?

Sleep is thought to be involved in the consolidation of new memories encoded during the day, as proposed by complementary learning systems accounts of memory. Other theories suggest that sleep's role in memory is not restricted to consolidation. The synaptic homeostasis hypothesis proposes that new learning is implemented in the brain through strengthening synaptic connections, a biologically costly process that gradually saturates encoding capacity during wake. During slow-wave sleep, synaptic strength is renormalized, thus restoring memory encoding ability. While the role of sleep in memory consolidation has been extensively documented, few human studies have explored the impact of sleep in restoring encoding ability, and none have looked at learning beyond episodic memory. In this registered report we test the predictions made by the complementary learning systems accounts and the synaptic homeostasis hypothesis regarding adult participants' ability to learn new words, and to integrate these words with existing knowledge. Participants took a polysomnographically-monitored daytime nap or remained awake prior to learning a set of new spoken words. Shortly after learning, and again on the following day, we measured participants' episodic memory for new words. We also assessed the degree to which newly learned words engage in competition with existing words. We predicted that sleep before encoding would result in better episodic memory for the words, and facilitate the overnight integration of new words with existing words. Based on existing literature and theory we further predicted that this restorative function is associated with slow-wave and sleep spindle activity. Our pre-registered analyses did not find a significant benefit of napping prior to encoding on word learning or integration. Exploratory analyses using a more sensitive measure of recall accuracy demonstrated significantly better performance in the nap condition compared to the no-nap condition in the immediate test. At the delayed test there was no longer a significant benefit of the nap. Of note, we found no significant effect of slow-wave activity prior to encoding on episodic memory or integration of newly learned words into the mental lexicon. However, we found that greater levels of Stage 2 sleep spindles were significantly associated with greater improvements in lexical competition from the immediate to the delayed test. Therefore, our results demonstrate some support for theories that implicate sleep spindles in restoring encoding capacity.

Nap effects on preschool children’s learning of letter‐sound mappings

This study explored whether a daytime nap aids children's acquisition of letter‐sound knowledge, which is a fundamental component for learning to read. Thirty‐two preschool children in Sydney, Australia (M_age = 4 years;3 months) were taught letter‐sound mappings in two sessions: one followed by a nap and the other by a wakeful period. Learning was assessed by explicit letter‐sound mappings (“Which sound does this letter make?”) and knowledge generalization tasks (“Here's Tav and Cav, which one is /kav/?”). Results from the knowledge generalization task showed better performance after a nap than after wake. However, no nap benefit was found for explicit letter‐sound knowledge. This study provides initial evidence that naps could be beneficial for preschool children's learning of letter‐sound mappings.

Word learning and lexicalization in a second language: Evidence from the Prime lexicality effect in masked form priming

In a masked form priming lexical decision task, orthographically related word primes cause null or inhibitory priming relative to unrelated controls because of lexical competition between primes and targets, whereas orthographically related nonword primes lead to facilitation because nonwords are not lexically represented and hence do not evoke lexical competition. This prime lexicality effect (PLE) has been used as an index of new word lexicalization in the developing lexicon by using to-be-learned words and their orthographic neighbors as primes and targets, respectively. Experiment 1 confirmed an inhibitory effect of −46 ms among native English speakers and faciliatory effects of 52 ms by Japanese English learners without critical word training. In Experiment 2, Japanese English learners studied novel English words while performing a meaning-based, form-based, or no task during learning. Recall measures indicated a dissociation between these two types of processing, with a form-based task leading to greater recall of L2 words and a meaning-based task leading to greater recall of L1 words. Results indicated that all three learning conditions produced neither facilitation nor inhibition (null priming effect). Taken together, the results of the two experiments demonstrate that the PLE can occur in a second language (L2) and that the training procedure can yield at least partial lexicalization of new L2 words.

Foreign Language Training to Stimulate Cognitive Functions

Adult development throughout a lifetime implies a series of changes in systems, including cognitive and linguistic functioning. The aim of this article is to study the effect of foreign language training on linguistic processing, particularly the frequency of the tip-of-the-tongue (TOT) phenomenon and on other cognitive processes such as processing speed and working memory in adults aged 40 to 60 years. Sixty-six healthy Colombian teachers were enrolled in this study. They were then randomly divided into an experimental group (33 healthy adults who underwent a four-week training period) and a passive control group (33 healthy adults who did not undergo any training). All participants performed induction tasks for the TOT phenomenon, working memory and processing speed before and after the four weeks. Results showed more of an effect in the semantic access, phonological access and processing speed measures with a better performance in the experimental group than in the control group. In Colombia, this type of training is still new and little is known to date about programs to prevent cognitive impairments. The need to conduct more studies confirming or refuting these findings is discussed, thus raising awareness about the extent of this type of training to increase the linguistic and cognitive performance of adults.

The effect of sleep on novel word learning in healthy adults: A systematic review and meta-analysis

There is increasing evidence to indicate that sleep plays a role in language acquisition and consolidation; however, there has been substantial variability in methodological approaches used to examine this phenomenon. This systematic review and meta-analysis aimed to investigate the effect of sleep on novel word learning in adults, and explore whether these effects differed by retrieval domain (i.e., recall, recognition, and tests of lexical integration). Twenty-five unique studies met the inclusion criteria for the review, and 42 separate outcome measures were synthesized in the meta-analysis (k = 29 separate between-group comparisons, n = 1,396 participants). The results from the omnibus meta-analysis indicated that sleep was beneficial for novel word learning compared with wakefulness (g = 0.50). Effect sizes differed across the separate domain-specific meta-analyses, with moderate effects for recall (g = 0.57) and recognition memory (g = 0.52), and a small effect for tasks which measured lexical integration (g = 0.39). Overall, the results of this meta-analysis indicate that sleep generally benefits novel word acquisition and consolidation compared with wakefulness across differing retrieval domains. This systematic review highlights the potential for sleep to be used to improve second-language learning in healthy adults, and overall provides further insight into methods to facilitate language development.

Timing storytime to maximize children's ability to retain new vocabulary

Shared storybook reading is a key aid to vocabulary acquisition during childhood. However, word learning research has tended to use unnaturalistic (explicit) training regimes. Using a storybook paradigm, we examined whether children (particularly those with weaker vocabularies) are more likely to retain new words if they learn them closer to sleep. Parents read their children (5- to 7-year-olds; N = 237) an alien adventure story that contained 12 novel words with illustrations at one of two training times: at bedtime or 3-5 h before bedtime. Using online tasks, parents tested their children's ability to recall the new words (production) and associate them with pictures (comprehension) immediately after hearing the story and again the following morning. As hypothesized, we replicated two findings. First, children showed overnight improvements in their ability to produce and comprehend new words when tested again the next day. Second, children with better existing vocabulary knowledge showed larger overnight gains in new word comprehension. Counter to expectations, overnight gains in comprehension were larger if the story was read 3-5 h before bedtime rather than at bedtime. These ecologically valid findings are consistent with theories that characterize word learning as a prolonged process supported by mechanisms such as consolidation and retrieval practice, with existing vocabulary knowledge acting as an important source of variability in retention. The findings provide preliminary evidence that encountering new words in stories later in the day (but not too close to sleep) may help to harness vocabulary growth and may be more beneficial than leaving shared storybook reading just for bedtime.

Integration of newly learned L2 words into the mental lexicon is modulated by vocabulary learning method

The aim of the study was to investigate both L2 word integration and the effect of learning method on it. For this purpose, an L2 word-learning paradigm was designed with two learning methods: L2 words were paired with videos in the first one and their translation-equivalent L1 words in the second. To test L2 word integration, a lexical decision task associated with form priming was administered before and after the learning phase. The L2 words to be learned were used as primes. Forty-eight participants participated in the study. Before learning, a facilitation effect was obtained with pseudowords (not already learned L2 words) as primes and L1 words as targets. After learning, L2 words no longer facilitated L1 word recognition when learned with the video method, while they still had this effect when learned with the L1 words - L2 words method. In accordance with the prime lexicality effect (PLE), this absence of a facilitation effect indicates that L1 words and L2 words are involved in a lexical competition process common to the two languages. This result highlights swift lexicalisation and demonstrates the effect of learning method in lexicalisation.

Something old, something new: A review of the literature on sleep-related lexicalization of novel words in adults

Word learning is a crucial aspect of human development that depends on the formation and consolidation of novel memory traces. In this paper, we critically review the behavioural research on sleep-related lexicalization of novel words in healthy young adult speakers. We first describe human memory systems, the processes underlying memory consolidation, then we describe the complementary learning systems account of memory consolidation. We then review behavioural studies focusing on novel word learning and sleep-related lexicalization in monolingual samples, while highlighting their relevance to three main theoretical questions. Finally, we review the few studies that have investigated sleep-related lexicalization in L2 speakers. Overall, while several studies suggest that sleep promotes the gradual transformation of initially labile traces into more stable representations, a growing body of work suggests a rich variety of time courses for novel word lexicalization. Moreover, there is a need for more work on sleep-related lexicalization patterns in varied populations, such as L2 speakers and bilingual speakers, and more work on individual differences, to fully understand the boundary conditions of this phenomenon.

Is that a pibu or a pibo? Children with reading and language deficits show difficulties in learning and overnight consolidation of phonologically similar pseudowords

Word learning is critical for the development of reading and language comprehension skills. Although previous studies have indicated that word learning is compromised in children with reading disability (RD) or developmental language disorder (DLD), it is less clear how word learning difficulties manifest in children with comorbid RD and DLD. Furthermore, it is unclear whether word learning deficits in RD or DLD include difficulties with offline consolidation of newly learned words. In the current study, we employed an artificial lexicon learning paradigm with an overnight design to investigate how typically developing (TD) children (N = 25), children with only RD (N = 93), and children with both RD and DLD (N = 34) learned and remembered a set of phonologically similar pseudowords. Results showed that compared to TD children, children with RD exhibited: (i) slower growth in discrimination accuracy for cohort item pairs sharing an onset (e.g. pibu‐pibo), but not for rhyming item pairs (e.g. pibu‐dibu); and (ii) lower discrimination accuracy for both cohort and rhyme item pairs on Day 2, even when accounting for differences in Day 1 learning. Moreover, children with comorbid RD and DLD showed learning and retention deficits that extended to unrelated item pairs that were phonologically dissimilar (e.g. pibu‐tupa), suggestive of broader impairments compared to children with only RD. These findings provide insights into the specific learning deficits underlying RD and DLD and motivate future research concerning how children use phonological similarity to guide the organization of new word knowledge.

Growing up with interfering neighbours: the influence of time of learning and vocabulary knowledge on written word learning in children

Evidence suggests that new vocabulary undergoes a period of strengthening and integration offline, particularly during sleep. Practical questions remain, however, including whether learning closer to bedtime can optimize consolidation, and whether such an effect varies with vocabulary ability. To examine this, children aged 8-12-years-old (n 59) were trained on written novel forms (e.g. BANARA) in either the morning (long delay) or the evening (short delay). Immediately after training and the next day, lexical competition (a marker of integration) was assessed via speeded semantic decisions to neighbouring existing words (e.g. BANANA); explicit memory was measured via recognition and recall tasks. There were no main effects indicating performance changes across sleep for any task, counter to studies of spoken word learning. However, a significant interaction was found, such that children with poorer vocabulary showed stronger lexical competition on the day after learning if there was a short delay between learning and sleep. Furthermore, while poorer vocabulary was associated with slower novel word recognition speed before and after sleep for the long delay group, this association was only present before sleep for the short delay group. Thus, weak vocabulary knowledge compromises novel word acquisition, and when there is a longer period of post-learning wake, this disadvantage remains after a consolidation opportunity. However, when sleep occurs soon after learning, consolidation processes can compensate for weaker encoding and permit lexical integration. These data provide preliminary suggestion that children with poorer vocabulary may benefit from learning new words closer to bedtime.

Eight-Section Brocade Exercises Improve the Sleep Quality and Memory Consolidation and Cardiopulmonary Function of Older Adults With Atrial Fibrillation-Associated Stroke

Purpose: Poor sleep quality is harmful for everyone and potentially even more harmful for older adults with atrial fibrillation-associated stroke (AFAS). This study aims to explore the effects of eight-section brocade (ESB) on sleep quality, memory, and cardiopulmonary function in the older adults with AFAS. Methods: Older adults with AFAS and sleep disorders were recruited and divided into the ESB (EG, n = 85) and control groups (CG, general exercise, n = 85). EG patients received 60 min ESB exercises 5 times a week for 12 weeks; CG patients received normal exercise. Pittsburgh sleep quality index (PSQI) scores (poor sleepers ≥8 and normal sleepers < 8), memory for word pairs (poor memory ≤ 7 and normal memory > 7), left ventricular posterior wall (LVPW) thickness, and maximum ventilation (MV, to evaluate cardiopulmonary function) values were measured. The correlation between sleep and memory quality was analyzed using PSQI scores and word pairs via the Pearson correlation coefficients test. Adjusted Cox models were used to explore an interaction between PSQI and ESB exercise. Results: After 12-week exercise intervention, ESB improved sleep quality, latency, duration, disturbance and daytime dysfunction when compared to conventional exercise. In similar cases, the MV values in the EG were also higher than that in the CG (p = 0.009). ESB intervention could not affect the cardiac structure and left ventricular ejection fraction. Compared with the CG, the ESB intervention reduced PSQI scores and increased memorized word pairs (p < 0.001 for poor and normal sleepers in both unadjusted and adjusted analysis, p = 0.012 and 0.003 for poor and normal memory). The test of Pearson correlation coefficients showed that PSQI scores were strongly associated with the number of word pairs in both unadjusted and adjusted analyses (p < 0.0001). Conclusion: Eight-section brocade exercise improved sleep quality and memory consolidation and cardiopulmonary function by reducing PSQI scores, increasing word pairs and MV values in the older adults with AFAS.

Reasons to doubt the generalizability, reliability, and diagnosticity of fast mapping (FM) for rapid lexical integration

The possibility of fast mapping (FM) promoting rapid lexical integration challenges complementary systems accounts of word learning. Here, we first question the diagnosticity of orthographic lexical competition prior to sleep as an indicator of lexical integration, given emerging evidence that the same pre-sleep effect can be found with explicit learning paradigms. Second, we describe a study that showed no evidence of accelerated lexical integration for spoken-word learning. This study also found no FM advantage when written materials were used . Taken together, the evidence does not convincingly demonstrate that FM can accelerate lexical integration in healthy adults.

Learning to live with interfering neighbours: the influence of time of learning and level of encoding on word learning

New vocabulary is consolidated offline, particularly during sleep; however, the parameters that influence consolidation remain unclear. Two experiments investigated effects of exposure level and delay between learning and sleep on adults' consolidation of novel competitors (e.g. BANARA) to existing words (e.g. BANANA). Participants made speeded semantic decisions (i.e. a forced choice: natural versus man-made) to the existing words, with the expectation that novel word learning would inhibit responses due to lexical competition. This competition was observed, particularly when assessed after sleep, for both standard and high exposure levels (10 and 20 exposures per word; Experiment 1). Using a lower exposure level (five exposures; Experiment 2), no post-sleep enhancement of competition was observed, despite evidence of consolidation when explicit knowledge of novel word memory was tested. Thus, when encoding is relatively weak, consolidation-related lexical integration is particularly compromised. There was no evidence that going to bed soon after learning is advantageous for overnight consolidation; however, there was some preliminary suggestion that longer gaps between learning and bed-onset were associated with better explicit memory of novel words one week later, but only at higher levels of exposure. These findings suggest that while lexical integration can occur overnight, weaker lexical traces may not be able to access overnight integration processes in the sleeping brain. Furthermore, the finding that longer-term explicit memory of stronger (but not weaker) traces benefit from periods of wake following learning deserves examination in future research.

Why and how the co-occurring familiar object matters in Fast Mapping (FM)? Insights from computational models

This article uses insights from computational semantic networks to explain why the co-occurring familiar objects are critical to the Fast Mapping (FM) procedure. I first propose that the co-occurring familiar objects provide the novel targets with a 'mimicry opportunity', which may facilitate the establishment of targets in long-term cortical memory networks. I then argue that the occurrence of rapid cortical learning may depend on how 'well-connected' the co-occurring familiar object is in long-term memory networks.

Brain Signatures of New (Pseudo-) Words: Visual Repetition in Associative and Non-associative Contexts

The contribution of two different training contexts to online, gradual lexical acquisition was investigated by event-related potentials (ERPs) elicited by new, word-like stimuli. Pseudowords were repeatedly preceded by a picture representing a well-known object (semantic-associative training context) or by a hash mark (non-associative training context). The two training styles revealed differential effects of repetition in both behavioral and ERPs data. Repetition of pseudowords not associated with any stimulus gradually enhanced the late positive component (LPC) as well as speeded lexical categorization of these stimuli, suggesting the formation of episodic memory traces. However, repetition under the semantic-associative context caused higher reduction in N400 component and categorization latencies. This result suggests the facilitation in the lexico-semantic processing of pseudowords as a consequence of their progressive associations to picture-concepts, going beyond the visual memory trace that is generated under the non-associative context.

Learning new meanings for known words: Perturbation of original meanings and retention of new meanings

Learning a new, unrelated meaning for a known word faces competition from the word's original meaning. Moreover, the connection of the word with its original meaning also shows a subtle form of interference, a perturbation, when tested immediately after learning. However, the long-term effects of both types of interference are unclear. The present study paired both high and low frequency words with new unrelated meanings, testing the fate of new and original meanings on three different days over one week as a function of word familiarity. The results were that learners maintained memory for new meanings of high frequency words better than the new meanings of low frequency words over one week. Following learning, meaning decisions on high frequency words that required the original meaning of the trained word were delayed relative to decisions on control words - but only when testing was immediate and the stimulus-onset asynchrony (SOA) between the trained word and its original meaning probe was 200 ms. When the SOA was 500 ms or when the test was delayed by one day or one week, no effect occurred. The findings indicate that in the learning of new meanings for known words, word familiarity benefits long-term retention of new meanings. The facilitation effect occurs along with a perturbation effect, in which the original meaning of a familiar word is made momentarily less accessible immediately after learning.

A Nap But Not Rest or Activity Consolidates Language Learning

Recent evidence suggests that a period of sleep after a motor learning task is a relevant factor for memory consolidation. However, it is yet open whether this also holds true for language-related learning. Therefore, the present study compared the short- and long-term effects of a daytime nap, rest, or an activity task after vocabulary learning on learning outcome. Thirty healthy subjects were divided into three treatment groups. Each group received a pseudo-word learning task in which pictures of monsters were associated with unique pseudo-word names. At the end of the learning block a first test was administered. Then, one group went for a 90-min nap, one for a waking rest period, and one for a resting session with interfering activity at the end during which a new set of monster names was to be learned. After this block, all groups performed a first re-test of the names that they initially learned. On the morning of the following day, a second re-test was administered to all groups. The nap group showed significant improvement from test to re-test and a stable performance onto the second re-test. In contrast, the rest and the interference groups showed decline in performance from test to re-test, with persistently low performance at re-test 2. The 3 (GROUP) × 3 (TIME) ANOVA revealed a significant interaction, indicating that the type of activity (nap/rest/interfering action) after initial learning actually had an influence on the memory outcome. These data are discussed with respect to translation to clinical settings with suggestions for improvement of intervention outcome after speech-language therapy if it is followed by a nap rather than interfering activity.