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For undergraduate students, excessive screen time is associated with poorer mental health and greater perceived stress.HighlightsExcessive screen time is associated with higher levels of stress.Cross-sectional sample of 513 college-aged young adults.Adiposity and aerobic fitness were unrelated to stress.In high active individuals, screen time is unrelated to stress.In low active individuals, greater sleep attenuates the screen time-stress relationship.

Scores on the ACT college entrance exam predict college grades to a statistically and practically significant degree, but what explains this predictive validity? The most obvious possibility is general intelligence—or psychometric “g”. However, inconsistent with this hypothesis, even when independent measures of g are statistically controlled, ACT scores still positively predict college grades. Here, in a study of 182 students enrolled in two Introductory Psychology courses, we tested whether pre-course knowledge, motivation, interest, and/or personality characteristics such as grit and self-control could explain the relationship between ACT and course performance after controlling for g. Surprisingly, none could. We speculate about what other factors might explain the robust relationship between ACT scores and academic performance.

Sleep deprivation impairs a wide range of cognitive processes, but the precise mechanism underlying these deficits is unclear. One prominent proposal is that sleep deprivation impairs vigilant attention, and that impairments in vigilant attention cause impairments in cognitive tasks that require attention. Here, we test this theory by studying the effects of caffeine on visual vigilant attention and on placekeeping, a cognitive control process that plays a role in procedural performance, problem solving, and other higher order tasks. In the evening, participants (N = 276) completed a placekeeping task (UNRAVEL) and a vigilant attention task (the Psychomotor Vigilance Task [PVT]) and were then randomly assigned to either stay awake overnight in the laboratory or sleep at home. In the morning, participants who slept returned to the lab, and all participants consumed a capsule that contained either 200 mg of caffeine or placebo. After an absorption period, all participants completed UNRAVEL and PVT again. Sleep deprivation impaired performance on both tasks, replicating previous work. Caffeine counteracted this impairment in vigilant attention but did not significantly affect placekeeping for most participants, though it did reduce the number of sleep-deprived participants who failed to maintain criterion accuracy. These results suggest that sleep deprivation impairs placekeeping directly through a causal pathway that does not include visual vigilant attention, a finding that has implications for intervention research and suggests that caffeine has limited potential to reduce procedural error rates in occupational settings. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Eyewitness memory researchers have recently devoted considerable attention to eyewitness confidence. While there is strong consensus that courtroom confidence is problematic, we now recognise that an eyewitness's initial confidence in their first identification - in certain contexts - can be of value. A few psychological scientists, however, have confidently, but erroneously claimed that in real-world cases, eyewitness initial confidence is the most important indicator of eyewitness accuracy, trumping all other factors that might exist in a case. This claim accompanies an exaggeration of the role of eyewitnesses' "initial confidence" in the DNA exoneration cases. Still worse, overstated claims about the confidence-accuracy relationship, and eyewitness memory, have reached our top scientific journals, news articles, and criminal cases. To set the record straight, we review what we actually know and do not know about the "initial confidence" of eyewitnesses in the DNA exoneration cases. Further reasons for skepticism about the value of the confidence-accuracy relationship in real-world cases come from new analyses of a separate database, the National Registry of Exonerations. Finally, we review new research that reveals numerous conditions wherein eyewitnesses with high initial confidence end up being wrong.

The current study examines the effect of sleep deprivation and caffeine use on racial bias in the decision to shoot. Participants deprived of sleep for 24 hr (vs. rested participants) made more errors in a shooting task and were more likely to shoot unarmed targets. A diffusion decision model analysis revealed sleep deprivation decreased participants’ ability to extract information from the stimuli, whereas caffeine impacted the threshold separation, reflecting decreased caution. Neither sleep deprivation nor caffeine moderated anti-Black racial bias in shooting decisions or at the process level. We discuss how our results clarify discrepancies in past work testing the impact of fatigue on racial bias in shooting decisions.

Sleep plays a role in the consolidation of various aspects of language learning. In this study, we investigated the extent to which sleep-dependent memory consolidation contributes to second language (L2) rule generalization and enhancement of L2 explicit knowledge. One hundred native English speakers were engaged in a meaning-focused training of two German grammar rules. Participants were trained either in the morning or in the evening and tested after a retention interval that was either filled with wakefulness or sleep. During the test, we used a grammaticality judgment test to measure grammatical learning and retrospective verbal reports and source attributions to measure awareness. We found that sleep consolidated learning only for learners who reported awareness of syntactic rules prior to sleep. However, performance based on explicit sources did not differ after a period of sleep and after a period of wakefulness. These findings suggest that sleep may benefit L2 rule generalization only for learners who are aware of the L2 rules before sleep but may not consolidate L2 explicit knowledge.

Listeners exposed to accented speech must adjust how they map between acoustic features and lexical representations such as phonetic categories. A robust form of this adaptive perceptual learning is learning to perceive synthetic speech where the connections between acoustic features and phonetic categories must be updated. Both implicit learning through mere exposure and explicit learning through directed feedback have previously been shown to produce this type of adaptive learning. The present study crosses implicit exposure and explicit feedback with the presence or absence of a written identification task. We show that simple exposure produces some learning, but explicit feedback produces substantially stronger learning, whereas requiring written identification did not measurably affect learning. These results suggest that explicit feedback guides learning of new mappings between acoustic patterns and known phonetic categories. We discuss mechanisms that may support learning via implicit exposure.

An emerging body of evidence has begun to document the beneficial after effects of single bouts — or doses — of physical activity for cognition. This article highlights a selection of common themes and critical delimitations that investigators new to this area of research as well as those currently working in the field may find relevant for advancing research in this area. The intent of this article is to provide a stimulus for future investigations to enhance not only the breadth and depth of the evidence, but also the experimental rigor. In doing so, a number of fundamental considerations are discussed including the aspects of cognition predominantly focused upon to date, issues related to the dose of the physical activity (i.e., how long the after effects persist, what characteristics of the dose may maximize the cognitive after effects), potential moderating variables, as well as potential underlying mechanisms. Additionally, discussion is provided regarding methodological considerations for future investigations including implications of the experimental design, control conditions, and cognitive assessment utilized, as well as statistical and reporting considerations to facilitate transparency. By calling attention to these areas, the hope is that future research may advance our understanding of the underlying mechanisms, theoretical development, and clinical relevance of the cognitive after effects of these single doses of physical activity.

Sleeping for a short period (i.e. napping) may help mitigate impairments in cognitive processing caused by sleep deprivation, but there is limited research on effects of brief naps in particular. Here, we tested the effect of a brief nap opportunity (30- or 60-min) during a period of sleep deprivation on two cognitive processes with broad scope, placekeeping and vigilant attention. In the evening, participants (N = 280) completed a placekeeping task (UNRAVEL) and a vigilant attention task (Psychomotor Vigilance Task [PVT]) and were randomly assigned to either stay awake overnight or sleep at home. Sleep-deprived participants were randomly assigned to receive either no nap opportunity, a 30-min opportunity, or a 60-min opportunity. Participants who napped were set up with polysomnography. The next morning, sleep participants returned, and all participants completed UNRAVEL and the PVT. Sleep deprivation impaired performance on both tasks, but nap opportunity did not reduce the impairment, suggesting that naps longer than those tested may be necessary to cause group differences. However, in participants who napped, more time spent in slow-wave sleep (SWS) was associated with reduced performance deficits on both tasks, effects we interpret in terms of the role of SWS in alleviating sleep pressure and facilitating memory consolidation.

Wixted et al. (in press. Doing right by the eyewitness evidence: A response to Berkowitz et al. Memory) remind us that they are aware of some conditions in which confidence does not trump all but suggest that initial high-confidence errors should be rare. In this reply, we draw attention to new lab research that continues to cast doubt on the value of an initial eyewitness identification made with high confidence. Additional data from field studies of police lineups lead us to conclude that it is far too risky in real-world cases to assume that eyewitnesses who have high initial confidence are also highly accurate. As a final point, we dispute Wixted et al.'s interpretation of "initial low confidence" in the DNA exoneration cases.

Background Characteristics of both teachers and learners influence mathematical learning. For example, when teachers use hand gestures to support instruction, students learn more than others who learn the same concept with only speech, and students with higher working memory capacity (WMC) learn more rapidly than those with lower WMC. One hypothesis for the effect of gesture on math learning is that gestures provide a signal to learners that can reduce demand on working memory resources during learning. However, it is not known what sort of working memory resources support learning with gesture. Gestures are motoric; they co-occur with verbal language and they are perceived visually. Methods In two studies, we investigated the relationship between mathematical learning with or without gesture and individual variation in verbal, visuospatial, and kinesthetic WMC. Students observed a videotaped lesson in a novel mathematical system that either included instruction with both speech and gesture (Study 1) or instruction with only speech (Study 2). After instruction, students solved novel problems in the instructed system and transfer problems in a related system. Finally, students completed verbal, visuospatial, and kinesthetic working memory assessments. Results There was a positive relationship between visuospatial WMC and math learning when gesture was present, but no relationship between visuospatial WMC and math learning when gesture was absent. Rather, when gesture was absent, there was a relationship between verbal WMC and math learning. Conclusion Providing gesture during instruction appears to change the cognitive resources recruited when learning a novel math task.

Introduction Slow wave sleep (SWS) strengthens memory for studied information, but research on the effect of sleep on information that is not intentionally remembered is scarce. Previous research from our lab suggests sleep consolidates some information that has been encoded incidentally, meaning that it has been acted on but not intentionally remembered. It remains unclear what determines which information is consolidated during sleep after incidental encoding and what aspects of sleep are related to this mnemonic benefit. In two experiments, we test the hypothesis that sleep consolidates strong but not weak memory traces following incidental encoding and assess the relationship between memory performance and sleep attributes. Methods In Experiment 1, we manipulated memory strength within- and between-subjects. Participants rated words one or three times (within) in a shallow or deep incidental encoding task (between). In the shallow task, participants counted vowels in each word; in the deep task, participants rated each word on a scale from ‘concrete’ to ‘abstract’. Following a 12-hour period containing sleep or wakefulness, participants took a surprise memory test. In Experiment 2, participants rated words one or three times in the deep encoding task, received an 8-hour sleep opportunity with partial PSG, and took the surprise memory test. Results In Experiment 1, participants remembered words better after sleep than wake regardless of number of encoding trials, but only after deep encoding. There was not an effect of sleep following shallow encoding. In Experiment 2, SWS correlated negatively with response latency for correctly recognized words encoded once, but not those encoded three times. That is, participants who received more SWS showed faster performance. Conclusion Results suggest sleep consolidated information based on the depth of encoding, and this benefit was related to SWS. This work is broadly consistent with theories of memory consolidation that predict sleep is more beneficial for strong than weak memory traces, such as the synaptic downscaling hypothesis. Support (if any)

Social media websites have dramatically increased in popularity. Information on these sites does not require verification and may be inaccurate. We investigated how familiarity with content and Twitter authors influenced false memory. Participants from Michigan State University (MSU) read an article about college basketball followed by a Twitter recap that contained false information. The article discussed either MSU or the University of Iowa; the Twitter feed was purportedly written by students from one of the schools in a 22 design. Lastly, participants completed recognition and source memory tests. Correct and false recognition were similar across conditions. In an analysis including source test results, we found higher false memory for the Iowa article than the MSU article. We also found an interaction between article and Twitter author, opposite of our hypothesis, such that false memory was greatest for conditions with incongruent article and Twitter author (e.g., Iowa article and MSU Twitter). Thus, we replicated earlier work showing higher memory distortion for unfamiliar content. We also found preliminary evidence that readers may take into account the relationship between authors and content. This is an important first step in understanding how false memory arises from social media, an everexpanding cultural influence. Overall correct and false memory were similar across misinformation conditions.Source test results revealed an effect of article and Twitter source congruence.False memory increased for groups with incongruent article and Twitter sources.Readers may assess validity of Twitter information based on author expertise.

Laptop computers are widely prevalent in university classrooms. Although laptops are a valuable tool, they offer access to a distracting temptation: the Internet. In the study reported here, we assessed the relationship between classroom performance and actual Internet usage for academic and nonacademic purposes. Students who were enrolled in an introductory psychology course logged into a proxy server that monitored their online activity during class. Past research relied on self-report, but the current methodology objectively measured time, frequency, and browsing history of participants’ Internet usage. In addition, we assessed whether intelligence, motivation, and interest in course material could account for the relationship between Internet use and performance. Our results showed that nonacademic Internet use was common among students who brought laptops to class and was inversely related to class performance. This relationship was upheld after we accounted for motivation, interest, and intelligence. Class-related Internet use was not associated with a benefit to classroom performance.

Sleep deprivation is increasingly common and poses serious problems for optimal cognitive functioning. Here we review the empirical literature on the consequences of sleep loss for working memory. The bulk of the research suggests that sleep is essential for working memory. Sleep deprivation inhibits general attentional and mnemonic abilities and influences neural activation in frontal and parietal cortices, areas critical for working memory. Decreases in task performance are typically accompanied by decreased activation in task-relevant areas under conditions of sleep deprivation. However, there is some evidence that deprivation can lead to increases in activation as a compensatory mechanism allowing for maintained performance. We conclude by discussing what is known about the remediation of these impairments through the use of caffeine and other stimulants.

False confession is a major contributor to the problem of wrongful convictions in the United States. Here, we provide direct evidence linking sleep deprivation and false confessions. In a procedure adapted from Kassin and Kiechel [(1996) Psychol Sci 7(3):125-128], participants completed computer tasks across multiple sessions and repeatedly received warnings that pressing the "Escape" key on their keyboard would cause the loss of study data. In their final session, participants either slept all night in laboratory bedrooms or remained awake all night. In the morning, all participants were asked to sign a statement, which summarized their activities in the laboratory and falsely alleged that they pressed the Escape key during an earlier session. After a single request, the odds of signing were 4.5 times higher for the sleep-deprived participants than for the rested participants. These findings have important implications and highlight the need for further research on factors affecting true and false confessions.

Introduction Slow wave sleep (SWS) strengthens declarative memory for information studied for a later test. However, research on the effect of sleep on information that is not intentionally remembered is scare. Previous research from our lab suggests sleep consolidates some, but not all, information that has been encoded incidentally, meaning that it has been acted on but not intentionally remembered. It remains unclear what determines which information benefits from sleep-dependent consolidation processes and what aspects of sleep are related to these mnemonic benefits. In two experiments, we test the hypothesis that sleep consolidates strong but not weak memory traces following incidental encoding, and assess the relationship between memory performance and objective sleep characteristics. Methods In Experiment 1, participants rated words one (weak traces) or three times (strong traces) in a deep or shallow incidental encoding task. Participants either rated words on a scale from ‘concrete’ to ‘abstract’ (deep) or counted the vowels in the words (shallow). Following a 12-hour period containing sleep or wakefulness, participants took a surprise memory test. In Experiment 2, participants rated words one or three times in the deep encoding task, received an 8-hour sleep opportunity with polysomnography, and took the surprise memory test. Results In Experiment 1, participants remembered words better after sleep than wake regardless of whether words were encoded one or three times, but only after deep encoding. Sleep did not consolidate information following shallow encoding. Experiment 2 is ongoing, but we predict that the amount of SWS will correlate positively with memory. Conclusion Results thus far suggest sleep may have consolidated information based on the strength of memory traces. Because deep encoding results in stronger memory traces than shallow encoding, this work is broadly consistent with theories of memory consolidation that predict sleep is more beneficial for strong memory traces than weak, such as the synaptic downscaling hypothesis. Support N/A

Introduction The effect of sleep on false memory is equivocal. In the Deese-Roediger-McDermott illusory memory paradigm, some work shows that sleep increases false recall whereas other work shows that sleep decreases false recognition. Given these ambiguous findings, we sought to investigate the effect of sleep on false memory using the misinformation paradigm. Methods Participants watched a short film depicting a home burglary, received misinformation about the film, and were tested on their memory for the film. The recognition test was given after a 12-hour retention interval that included either sleep or wake. We manipulated the time at which participants received misinformation. Half were given misinformation after encoding (before sleep or wake) and the other half were given misinformation after the retention interval (after sleep or wake). Results There was a main effect of condition on correct recognition; participants in the sleep group showed higher correct recognition than those in the wake group. On false memory, there was a main effect of timing of misinformation and an interaction between condition and timing of misinformation. That is, the effect of sleep on false memory depended on when misinformation was administered. If misinformation was given after the retention interval, false memory tended to be lower after sleep than wake whereas if misinformation was given before the retention interval, false memory tended to be higher after sleep than wake. Conclusion Sleep can both protect against and facilitate memory distortion depending on when misinformation is encountered. These results inform our understanding of consolidation processes. When consolidation acts on true memory alone, it strengthens that memory making it resistant to distortion. Conversely, when misinformation is presented before consolidation, sleep may integrate misinformation into memory for the true event, increasing distortion. This work has important theoretical implications for memory consolidation and important applied implications for interrogation practices. Support N/A

In a large sample (N = 234), we tested effects of 24-hr of sleep deprivation on error rates in a procedural task that requires memory maintenance of task-relevant information. In the evening, participants completed the task under double-blind conditions and then either stayed awake in the lab overnight or slept at home. In the morning, participants completed the task again. Sleep-deprived participants were more likely to suffer a general breakdown in ability (or willingness) to meet a modest accuracy criterion they had met the night before. Among sleep-deprived participants who could still perform the task, error rates were elevated, and errors reflecting memory failures increased with time-on-task. The results suggest that sleep-deprived individuals should not perform procedural tasks associated with interruptions and costly errors-or, if they must, they should perform such tasks only for short periods. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

The negativity bias is the tendency for individuals to give greater weight, and often exhibit more rapid and extreme responses, to negative than positive information. Using the Deese-Roediger-McDermott illusory memory paradigm, the current study sought to examine how the negativity bias might affect both correct recognition for negative and positive words and false recognition for associated critical lures, as well as how trait neuroticism might moderate these effects. In two experiments, participants studied lists of words composed of semantic associates of an unpresented word (the critical lure). Half of the lists were comprised of positive words and half were comprised of negative words. As expected, individuals remembered negative list words better than positive list words, consistent with a negativity bias in correct recognition. When tested immediately (Experiment 1), individuals also exhibited greater false memory for negative versus positive critical lures. When tested after a 24-hr delay (Experiment 2), individuals higher in neuroticism maintained greater false memory for negative versus positive critical lures, but those lower in neuroticism showed no difference in false memory between negative and positive critical lures. Possible mechanisms and implications for mental health disorders are discussed.

Inaccurate eyewitness identifications are the leading cause of known false convictions in the United States. Moreover, improving eyewitness memory is difficult and often unsuccessful. Sleep consistently strengthens and protects memory from interference, particularly when a recall test is used. However, the effect of sleep on recognition memory is more equivocal. Eyewitness identification tests are often recognition based, thus leaving open the question of how sleep affects recognition performance in an eyewitness context. In the current study, we investigated the effect of sleep on eyewitness memory. Participants watched a video of a mock-crime and attempted to identify the perpetrator from a simultaneous lineup after a 12-hour retention interval that either spanned a waking day or night of sleep. In Experiment 1, we used a target-present lineup and, in Experiment 2, we used a target-absent lineup in order to investigate correct and false identifications, respectively. Sleep reduced false identifications in the target-absent lineup (Experiment 2) but had no effect on correct identifications in the target-present lineup (Experiment 1). These results are discussed with respect to memory strength and decision making strategies.

Laptop computers are widely prevalent in university classrooms. Although laptops are a valuable tool, they offer access to a distracting temptation: the Internet. In the study reported here, we assessed the relationship between classroom performance and actual Internet usage for academic and nonacademic purposes. Students who were enrolled in an introductory psychology course logged into a proxy server that monitored their online activity during class. Past research relied on self-report, but the current methodology objectively measured time, frequency, and browsing history of participants' Internet usage. In addition, we assessed whether intelligence, motivation, and interest in course material could account for the relationship between Internet use and performance. Our results showed that nonacademic Internet use was common among students who brought laptops to class and was inversely related to class performance. This relationship was upheld after we accounted for motivation, interest, and intelligence. Class-related Internet use was not associated with a benefit to classroom performance.

The use of laptops and cell phones in the classroom is increasing but there is little research assessing whether these devices create distraction that diminishes learning. Moreover, the contribution of intellectual ability to the relationship between learning and portable device use has not been thoroughly investigated. To bridge this gap, students in an introductory psychology class were surveyed about the frequency and duration of their use of various portable devices in the classroom. Internet use negatively predicted exam scores and added to the prediction of classroom learning, above a measure of intellectual ability. Furthermore, students discounted the effect of using portable devices on learning over time. Concomitantly, those with higher intellectual ability reported using the internet more in class over time. Thus, higher rates of internet use were associated with lower test grades and students' beliefs about this relationship did not reflect their ability to multi-task effectively.

Sleep-dependent consolidation has been demonstrated for declarative and procedural memory but few theories of consolidation distinguish between rote and generalized learning, suggesting similar consolidation should occur for both. However, studies using rote and generalized learning have suggested different patterns of consolidation may occur, although different tasks have been used across studies. Here we directly compared consolidation of rote and generalized learning using a single speech identification task. Training on a large set of novel stimuli resulted in substantial generalized learning, and sleep restored performance that had degraded after 12 waking hours. Training on a small set of repeated stimuli primarily resulted in rote learning and performance also degraded after 12 waking hours but was not restored by sleep. Moreover performance was significantly worse 24-h after rote training. Our results suggest a functional dissociation between the mechanisms of consolidation for rote and generalized learning which has broad implications for memory models.

Despite positive associations between chronic physical activity and memory; we have little understanding of how best to incorporate physical activity during the day to facilitate the consolidation of information into memory, nor even how time spent physically active during the day relates to memory processes. The purpose of this investigation was to examine the relation between physical activity during the day and long-term memory. Ninety-two young adults learned a list of paired-associate items and were tested on the items after a 12-hour interval during which heart rate was recorded continuously. Although the percentage of time spent active during the day was unrelated to memory, two critical physical activity periods were identified as relating to the maintenance of long-term memory. Engaging in physical activity during the period 1 to 2-hours following the encoding of information was observed to be detrimental to the maintenance of information in long-term memory. In contrast, physical activity during the period 1-hour prior to memory retrieval was associated with superior memory performance, likely due to enhanced retrieval processing. These findings provide initial evidence to suggest that long-term memory may be enhanced by more carefully attending to the relative timing of physical activity incorporated during the day.

When memory is tested after a delay, performance is typically better if the retention interval includes sleep. However, it is unclear what accounts for this well-established effect. It is possible that sleep enhances the retrieval of information, but it is also possible that sleep protects against memory loss that normally occurs during waking activity. We developed a new research approach to investigate these possibilities. Participants learned a list of paired-associate items and were tested on the items after a 12-h interval that included waking or sleep. We analyzed the number of items gained versus the number of items lost across time. The sleep condition showed more items gained and fewer items lost than did the wake condition. Furthermore, the difference between the conditions (favoring sleep) in lost items was greater than the difference in gain, suggesting that loss prevention may primarily account for the effect of sleep on declarative memory consolidation. This finding may serve as an empirical constraint on theories of memory consolidation.

Early research on visual imagery led investigators to suggest that mental visual images are just weak versions of visual percepts. Later research helped investigators understand that mental visual images differ in deeper and more subtle ways from visual percepts. Research on motor imagery has yet to reach this mature state, however. Many authors have implicitly subscribed to the view that motor images are just weak versions of physical actions. We tested this view by comparing motor learning in variable practice conditions with motor learning in constant practice conditions when participants either physically or mentally practiced golf-putting. We found that physical and mental practice both resulted in significant learning but that variable practice was only better than constant practice when participants practiced physically. This outcome was not predicted by the hypothesis that motor imagery is just a weaker form of real-action experience.

Several studies have shown that sleep contributes to the successful maintenance of previously encoded information. This research has focused exclusively on memory for studied events, as opposed to false memories. Here we report three experiments showing that sleep reduces false memories in the Deese-Roediger-McDermott (DRM) memory illusion. False recognition of nonstudied words was reduced after sleep, relative to an equal retention interval of wakefulness, with no change in correct recognition of studied words. These experiments are the first to show that false memories can be reduced following sleep, and they extend the benefits of sleep to include increased accuracy of episodic memory.

Two groups of listeners, one of native speakers of a tone language (Mandarin Chinese) and one of native speakers of a non-tone language (English) were trained to recognize Cantonese lexical tones. Performance before and after training was measured using closed response-set identification and pairwise difference rating tasks. Difference ratings were submitted to multidimensional scaling (MDS) analyses to investigate training-related changes in listeners’ perceptual space. Both groups showed comparable initial performance and significant improvement in tone identification following training. However, the two groups differed in terms of the tones they found most difficult to identify, and in terms of the tones that were learned best. Differences between the two groups’ training-induced changes in identification (confusions) and perceptual spaces demonstrated that listeners’ native language experience with intonational as well as tone categories affects the perception and acquisition of non-native suprasegmental categories.

Purpose Investigate training-related changes in acoustic−phonetic representation of consonants produced by a text-to-speech (TTS) computer speech synthesizer. Method Forty-eight adult listeners were trained to better recognize words produced by a TTS system. Nine additional untrained participants served as controls. Before and after training, participants were tested on consonant recognition and made pairwise judgments of consonant dissimilarity for subsequent multidimensional scaling (MDS) analysis. Results Word recognition training significantly improved performance on consonant identification, although listeners never received specific training on phoneme recognition. Data from 31 participants showing clear evidence of learning (improvement ≥ 10 percentage points) were further investigated using MDS and analysis of confusion matrices. Results show that training altered listeners’ treatment of particular acoustic cues, resulting in both increased within-class similarity and between-class distinctiveness. Some changes were consistent with current models of perceptual learning, but others were not. Conclusion Training caused listeners to interpret the acoustic properties of synthetic speech more like those of natural speech, in a manner consistent with a flexible-feature model of perceptual learning. Further research is necessary to refine these conclusions and to investigate their applicability to other training-related changes in intelligibility (e.g., associated with learning to better understand dysarthric speech or foreign accents).

Noam Chomsky's work on ‘generative grammar’ led to the concept of a set of rules that can generate a natural language with a hierarchical grammar, and the idea that this represents a uniquely human ability. In a series of experiments with European starlings, in which several types of ‘warble’ and ‘rattle’ took the place of words in a human language, the birds learnt to classify phrase structure grammars in a way that met the same criteria. Their performance can be said to be almost human on this yardstick. So if there are language processing capabilities that are uniquely human, they may be more context-free or at a higher level in the Chomsky hierarchy. Or perhaps there is no single property or processing capacity that differentiates human language from non-human communication systems. Humans regularly produce new utterances that are understood by other members of the same language community1. Linguistic theories account for this ability through the use of syntactic rules (or generative grammars) that describe the acceptable structure of utterances2. The recursive, hierarchical embedding of language units (for example, words or phrases within shorter sentences) that is part of the ability to construct new utterances minimally requires a ‘context-free’ grammar2,3 that is more complex than the ‘finite-state’ grammars thought sufficient to specify the structure of all non-human communication signals. Recent hypotheses make the central claim that the capacity for syntactic recursion forms the computational core of a uniquely human language faculty4,5. Here we show that European starlings (Sturnus vulgaris) accurately recognize acoustic patterns defined by a recursive, self-embedding, context-free grammar. They are also able to classify new patterns defined by the grammar and reliably exclude agrammatical patterns. Thus, the capacity to classify sequences from recursive, centre-embedded grammars is not uniquely human. This finding opens a new range of complex syntactic processing mechanisms to physiological investigation.

Psychometric intelligence (g) is often conceptualized as the capability for online information processing but it is also possible that intelligence may be related to offline processing of information. Here, we investigated the relationship between psychometric g and sleep-dependent memory consolidation. Participants studied paired-associates and were tested after a 12-hour retention interval that consisted entirely of wake or included a regular sleep phase. We calculated the number of word-pairs that were gained and lost across the retention interval. In a separate session, participants completed a battery of cognitive ability tests to assess g. In the wake group, g was not correlated with either memory gain or memory loss. In the sleep group, we found that g correlated positively with memory gain and negatively with memory loss. Participants with a higher level of general intelligence showed more memory gain and less memory loss across sleep. Importantly, the correlation between g and memory loss was significantly stronger in the sleep condition than in the wake condition, suggesting that the relationship between g and memory loss across time is specific to time intervals that include sleep. The present research suggests that g not only reflects the capability for online cognitive processing, but also reflects capability for offline processes that operate during sleep.

© The Author(s) 2014. Many studies have investigated factors that affect susceptibility to false memories. However, few have investigated the role of sleep deprivation in the formation of false memories, despite overwhelming evidence that sleep deprivation impairs cognitive function. We examined the relationship between self-reported sleep duration and false memories and the effect of 24 hr of total sleep deprivation on susceptibility to false memories. We found that under certain conditions, sleep deprivation can increase the risk of developing false memories. Specifically, sleep deprivation increased false memories in a misinformation task when participants were sleep deprived during event encoding, but did not have a significant effect when the deprivation occurred after event encoding. These experiments are the first to investigate the effect of sleep deprivation on susceptibility to false memories, which can have dire consequences.