Caffeine consumption and sleep in a submarine environment: An observational study.

Submariners face many environmental and operational challenges to maintaining good sleep, including suboptimal lighting, shift work, and frequent interruptions. Anecdotally, many Sailors consume caffeine to alleviate the effects of poor sleep on alertness, mood, and performance; however, caffeine itself may also degrade sleep quantity and/or quality. This study provides the first exploration of the potential relationship between caffeine use and sleep onboard submarines. Objective measures (wrist actigraphy, available from 45 participants), self-report sleep metrics, and self-reported caffeine consumption were collected from 58 US Navy Sailors before and during a routine submarine underway at sea lasting 30 days. Contrary to expectations, less caffeine was reportedly consumed at sea (232.8 ± 241.1 mg) than on land prior to the underway (M = 284.4 ± 251.7 mg; X2 (1) = 7.43, p = 0.006), positive rather than negative relationships were observed between caffeine consumption and sleep efficiency (F = 6.11, p = 0.02), and negative relationships were observed between caffeine consumption and wake after sleep onset (F = 9.36, p = 0.004) and sleep fragmentation (F = 24.73, p < 0.0001). However, in contrast, higher caffeine consumption was also negatively related to self-reported sleep duration while at sea (F = 4.73, p = 0.03). This observational study is the first to measure relationships between caffeine consumption and sleep quantity and/or quality in a submarine environment. We propose that the unique submarine environment and the unique caffeine consumption patterns of submariners should be considered in the development of potential countermeasures for sleepiness.

Language is activated by visual input regardless of memory demands or capacity.

In the present study, we provide compelling evidence that viewing objects automatically activates linguistic labels and that this activation is not due to task-specific memory demands. In two experiments, eye-movements of English speakers were tracked while they identified a visual target among an array of four images, including a phonological competitor (e.g., flower-flag). Experiment 1 manipulated the capacity to subvocally rehearse the target label by imposing linguistic, spatial, or no working memory load. Experiment 2 manipulated the need to encode target objects by presenting target images either before or concurrently with the search display. While the timing and magnitude of competitor activation varied across conditions, we observed consistent evidence of language activation regardless of the capacity or need to maintain object labels in memory. We propose that language activation is automatic and not contingent upon working memory capacity or demands, and conclude that objects' labels influence visual search.

How a picture becomes a word: individual differences in the development of language-mediated visual search.

Over the course of our lifetimes, we accumulate extensive experience associating the things that we see with the words we have learned to describe them. As a result, adults engaged in a visual search task will often look at items with labels that share phonological features with the target object, demonstrating that language can become activated even in non-linguistic contexts. This highly interactive cognitive system is the culmination of our linguistic and visual experiences-and yet, our understanding of how the relationship between language and vision develops remains limited. The present study explores the developmental trajectory of language-mediated visual search by examining whether children can be distracted by linguistic competitors during a non-linguistic visual search task. Though less robust compared to what has been previously observed with adults, we find evidence of phonological competition in children as young as 8 years old. Furthermore, the extent of language activation is predicted by individual differences in linguistic, visual, and domain-general cognitive abilities, with the greatest phonological competition observed among children with strong language abilities combined with weaker visual memory and inhibitory control. We propose that linguistic expertise is fundamental to the development of language-mediated visual search, but that the rate and degree of automatic language activation depends on interactions among a broader network of cognitive abilities.

Effects of sleep and fatigue on teams in a submarine environment.

Successful submarine operations rely on the performance of tactical teams who must work under conditions of physiological and cognitive fatigue. Sleep loss and circadian disruption contribute to fatigue in this setting and, although the effects of this fatigue have been studied extensively in individuals, little is understood about how fatigue impacts team performance Рespecially in a submarine environment. The present review provides an overview of the fatigue on submarine teams and is divided into four main sections: 1) A discussion of factors that should be considered in team fatigue research. 2) An outline of how sleep and circadian rhythms of submariners are impacted by submarine-specific factors. 3) A discussion of the known effects of fatigue from sleep loss and circadian disruption on individual performance. 4) A consideration of how this fatigue impacts team performance. As the submarine force has recognized the need to protect submariner sleep and improve team dynamics, it is vital that future research accounts for the interplay between these two factors.

Acute Exposure to Low-to-Moderate Carbon Dioxide Levels and Submariner Decision Making.

BACKGROUND: Submarines routinely operate with higher levels of ambient carbon dioxide (CO2) (i.e., 2000 - 5000 ppm) than what is typically considered normal (i.e., 400 - 600 ppm). Although significant cognitive impairments are rarely reported at these elevated CO2 levels, recent studies using the Strategic Management Simulation (SMS) test have found impairments in decision-making performance during acute CO2 exposure at levels as low as 1000 ppm. This is a potential concern for submarine operations, as personnel regularly make mission-critical decisions that affect the safety and efficiency of the vessel and its crew while exposed to similar levels of CO2. The objective of this study was to determine if submariner decision-making performance is impacted by acute exposure to levels of CO2 routinely present in the submarine atmosphere during sea patrols. METHODS: Using a subject-blinded balanced design, 36 submarine-qualified sailors were randomly assigned to receive 1 of 3 CO2 exposure conditions (600, 2500, or 15,000 ppm). After a 45-min atmospheric acclimation period, participants completed an 80-min computer-administered SMS test as a measure of decision making. RESULTS: There were no significant differences for any of the nine SMS measures of decision making between the CO2 exposure conditions. DISCUSSION: In contrast to recent research demonstrating cognitive deficits on the SMS test in students and professional-grade office workers, we were unable to replicate this effect in a submariner population-even with acute CO2 exposures more than an order of magnitude greater than those used in previous studies that demonstrated such effects.Rodeheffer CD, Chabal S, Clarke JM, Fothergill DM. Acute exposure to low-to-moderate carbon dioxide levels and submariner decision making. Aerosp Med Hum Perform. 2018; 89(6):520-525.

Audio-visual object search is changed by bilingual experience.

The current study examined the impact of language experience on the ability to efficiently search for objects in the face of distractions. Monolingual and bilingual participants completed an ecologically-valid, object-finding task that contained conflicting, consistent, or neutral auditory cues. Bilinguals were faster than monolinguals at locating the target item, and eye movements revealed that this speed advantage was driven by bilinguals' ability to overcome interference from visual distractors and focus their attention on the relevant object. Bilinguals fixated the target object more often than did their monolingual peers, who, in contrast, attended more to a distracting image. Moreover, bilinguals', but not monolinguals', object-finding ability was positively associated with their executive control ability. We conclude that bilinguals' executive control advantages extend to real-world visual processing and object finding within a multi-modal environment.

Speakers of different languages process the visual world differently.

Language and vision are highly interactive. Here we show that people activate language when they perceive the visual world, and that this language information impacts how speakers of different languages focus their attention. For example, when searching for an item (e.g., clock) in the same visual display, English and Spanish speakers look at different objects. Whereas English speakers searching for the clock also look at a cloud, Spanish speakers searching for the clock also look at a gift, because the Spanish names for gift (regalo) and clock (reloj) overlap phonologically. These different looking patterns emerge despite an absence of direct language input, showing that linguistic information is automatically activated by visual scene processing. We conclude that the varying linguistic information available to speakers of different languages affects visual perception, leading to differences in how the visual world is processed.

Task dependent lexicality effects support interactive models of reading: a meta-analytic neuroimaging review.

Models of reading must explain how orthographic input activates a phonological representation, and elicits the retrieval of word meaning from semantic memory. Comparisons between tasks that theoretically differ with respect to the degree to which they rely on connections between orthographic, phonological and semantic systems during reading can thus provide valuable insight into models of reading, but such direct comparisons are not well-represented in the literature. An ALE meta-analysis explored lexicality effects directly contrasting words and pseudowords using the lexical decision task and overt or covert naming, which we assume rely most on the semantic and phonological systems, respectively. Interactions between task and lexicality effects demonstrate that different demands of the lexical decision and naming tasks lead to different manifestations of lexicality effects.

Differential recruitment of executive control regions during phonological competition in monolinguals and bilinguals.

Behavioral research suggests that monolinguals and bilinguals differ in how they manage within-language phonological competition when listening to language. The current study explored whether bilingual experience might also change the neural resources recruited to control spoken-word competition. Seventeen Spanish-English bilinguals and eighteen English monolinguals completed an fMRI task in which they searched for a picture representing an aurally presented word (e.g., "candy") from an array of four presented images. On competitor trials, one of the objects in the display shared initial phonological overlap with the target (e.g., candle). While both groups experienced competition and responded more slowly on competitor trials than on unrelated trials, fMRI data suggest that monolinguals, but not bilinguals, activated executive control regions (e.g., anterior cingulate, superior frontal gyrus) during within-language phonological competition. We conclude that differences in how monolinguals and bilinguals manage competition may result from bilinguals' more efficient deployment of neural resources.

CLEARPOND: cross-linguistic easy-access resource for phonological and orthographic neighborhood densities.

Past research has demonstrated cross-linguistic, cross-modal, and task-dependent differences in neighborhood density effects, indicating a need to control for neighborhood variables when developing and interpreting research on language processing. The goals of the present paper are two-fold: (1) to introduce CLEARPOND (Cross-Linguistic Easy-Access Resource for Phonological and Orthographic Neighborhood Densities), a centralized database of phonological and orthographic neighborhood information, both within and between languages, for five commonly-studied languages: Dutch, English, French, German, and Spanish; and (2) to show how CLEARPOND can be used to compare general properties of phonological and orthographic neighborhoods across languages. CLEARPOND allows researchers to input a word or list of words and obtain phonological and orthographic neighbors, neighborhood densities, mean neighborhood frequencies, word lengths by number of phonemes and graphemes, and spoken-word frequencies. Neighbors can be defined by substitution, deletion, and/or addition, and the database can be queried separately along each metric or summed across all three. Neighborhood values can be obtained both within and across languages, and outputs can optionally be restricted to neighbors of higher frequency. To enable researchers to more quickly and easily develop stimuli, CLEARPOND can also be searched by features, generating lists of words that meet precise criteria, such as a specific range of neighborhood sizes, lexical frequencies, and/or word lengths. CLEARPOND is freely-available to researchers and the public as a searchable, online database and for download at http://clearpond.northwestern.edu.