https://en.wikipedia.org/wiki/Information_warfare Part of a series on War (outline) History Military Battlespace Weapons Tactics Operational Strategy Grand strategy Administrative Organization Personnel Logistics Science Law Theory Non-warfare Culture Books Related Lists vte Information warfare (IW) is the battlespace use and management of information and communication technology (ICT) in pursuit of a competitive advantage over an opponent. It is different from cyberwarfare that attacks computers, software, and command control systems. Information warfare is the manipulation of information trusted by a target without the target's awareness so that the target will make decisions against their interest but in the interest of the one conducting information warfare.[1][2] As a result, it is not clear when information warfare begins, ends, and how strong or destructive it is.[3] Information warfare may involve the collection of tactical information, assurance(s) that one's information is valid, spreading of propaganda or disinformation to demoralize or manipulate[4] the enemy and the public, undermining the quality of the opposing force's information, and denial of information-collection opportunities to opposing forces. Information warfare is closely linked to psychological warfare.[5] ---- http://www.koreanlii.or.kr/w/index.php/Cognitive_warfare?ckattempt=1 Cognitive warfare (인지전/認知戰) consists of any military activities designed to affect attitudes and behaviors, by influencing, protecting, or disrupting individual, group, or population level cognition.[1] Cognitive warfare is an extension of information warfare using propaganda and disinformation.[2] Other methods of cognitive warfare include the targeted use of inaudible sound waves (frequency of <20 Hz) and microwaves to incapacitate enemy forces by disrupting the neurological functions of human targets without causing visible injury. According to the U.S. National Institute of Health, infrasound's effect on the human inner ear includes “vertigo, imbalance, intolerable sensations, incapacitation, disorientation, nausea, vomiting, and bowel spasm; and resonances in inner organs, such as the heart." While psychological warfare in the past utilized balloon flyers containing propaganda leaflets and plenty of USB, and radio and TV broadcasts against enemy forces, cognitive warfare differs in that it mainly utilizes various global media and social media. Cognitive warfare also aims to make political leaders and the population of the enemy country give up their will to wage war. In particular, fake information and black propaganda are spread through various media, including social media. As such, cognitive warfare has been referred to as the sixth battlefield, with 'human' as the main target after land, sea, air, cyber, and space.[3] [One sentence tip] 인지전이란 소셜미디어를 포함한 다양한 플랫폼을 통해 허위 정보와 심리적 전술을 사용하여 상대방의 인식을 조작하고 영향을 미치는 전쟁 방식을 말한다. Source: ResearchGate [Caption] 인지전을 다른 유사 형태의 전쟁 개념과의 관련성을 서로 비교한 다이아그램. Source: Conceptual relationship among Cognitive warfare and other types of warfare. ---------- China and Russia spearheading cognitive warfare Originally, cognitive warfare was materialized as a concept related to psychological warfare in socialist countries such as China and Russia. According to a paper titled “The Concept of Cognitive Warfare and Its Implications for South Korea's Defense,” published by the Korea Institute for National Defense Studies, China has emphasized the use of information since the Sun Tzu's Art of War, and information warfare was a key element during the Maoist Revolutionary War. This led to China's “three warfare strategies” (psychological warfare, public opinion warfare, and legal warfare) in the 2000s. Russia's information warfare is based on the concept of “reflexive control,” coined by Lefebvre in the 1960s, and has since evolved into cognitive warfare. Reflexive control refers to “shifting an adversary's decisions to the friendly side's intentions by providing the adversary with a rationale for making decisions. In response, in 2017, the U.S. Army defined cognitive warfare as “non-lethal warfare that undermines and destroys an enemy's offensive warfare and will to fight by manipulating the cognitive mechanisms of combatants and civilians engaged in war or combat,” and began to reorganize its resources and systems. Ukraine-Russia war Social media cognitive warfare was actively utilized by the Ukrainian military in the war. On April 17, 2022, it destroyed a Russian Black Sea Fleet cruiser, the Moscow, with an anti-ship missile, and then shared photos of the moment before it sank with the world via Twitter. Ukrainian President Zelensky also maintains strategic communication with the world on X (formerly Twitter), and Ukrainian military brigade-level combat units use Facebook to communicate major operations and combat achievements. Israel-Hamas war Cognitive warfare is in full swing in the Middle East. Since the start of the Israel's ground war in Gaza, international public opinion has gradually turned against Israel as Hamas has accused the Israeli military of indiscriminate attacks on humanitarian facilities such as hospitals and schools and civilians through social media. In November 2023, Hamas informed the world that the Israeli army had bombed a hospital facility, a humanitarian space, and a general from the Israeli army's Spokesperson's Unit came forward to explain that the Israeli army had attacked a Hamas military facility by showing Hamas's guns and weapons in the basement of the hospital. In this way, the Israeli Spokesperson's Unit (이스라엘 대변인부대) is acting as a “fake news fact-checking death squad. It is a “game-changer” that underscores the legitimacy of the Israeli military's pre-emptive strike.[5] Even when the Israeli army entered Gaza, it posted a message on Twitter (now X) at midnight saying that “ground forces and air forces are attacking Gaza simultaneously." This was widely reported by major media outlets around the world, including the Washington Post and AFP. Hamas then decided that the Israeli army was actually conducting a ground operation and exposed its weapons and troops, including tanks and rockets, hidden in underground facilities, to the surface and deployed them throughout Gaza. Immediately, the Israeli army used reconnaissance satellites and various unmanned aerial vehicles to identify Hamas strongholds and tunnel entrances, mobilized fighter jets, and launched precision strikes with bombs and missiles. The Israeli army also shared these videos in real time on social media. This was done to prevent Hamas from spreading fake news about Israel's misbehavior and overreaction, and to instill fear among Hamas members. Psychological warfare between North and South Korea Cognitive warfare using social media has already begun on the Korean Peninsula. North Korea has recently increased its provocations, including reinstating GPs (frontline guard posts) after declaring its intention to abandon the September 19 inter-Korean military agreement, and in response, South Korea has been broadcasting propaganda loudspeakers to the North, and North Korean defector organizations have been sending leaflets and USBs containing the truth about the Kim family and the reality of South Korea's freedom along with one-dollar bills to North Korean areas, despite the government's urging. [6] In response, North Korea has also been making offensive loudspeaker broadcasts and releasing balloons containing garbage and filth over South Korea. In a similar situation, North Korea is likely to use social media to spread fake news.[7] References ↑ A classic example of cognitive warfare is found in the Bible. In Judges ch.7, when Israel was a tribal nation, the neighboring Midianite and Amalekites attacked Israel. Jehovah chose Gideon, a man of faith, to lead Israel against the enemy. Gideon sent out to the 12 tribes to recruit men and chose 300 men who were willing and able to fight. They prepared trumpets, torches, and empty jars, instead of swords and weapons, as the LORD had commanded. Taking advantage of the darkness of the night, they surrounded the enemy camps and, at Gideon's signal, blew their trumpets, broke their empty jars, held their torches aloft, and shouted, “For the LORD, for Gideon!” The sleeping enemy soldiers were quickly thrown into great confusion and began to flee, striking each other with their swords. Gideon blew the trumpet again, and ordered to chase the enemy to the border. Gideon's 300 men were victorious and unharmed. ↑ NATO General Paolo Ruggiero distinguishes cognitive warfare from other information-related activities by its objectives: "Its goal is not what individuals think, but rather, the way they think." Exponents of cognitive warfare aim to influence human thought, reasoning, sense-making, decision-making, and behavior, through the manipulation of information and use of machine learning structures which distribute information on the internet. ↑ Yoo Yong-won, Cognitive warfare growing in power in actual warfare, Chosun Ilbo. November 30, 2023. ↑ Masakowski, Yvonne, PhD. (April 11, 2022). "Newport Lecture Series: "Artificial Intelligence & Cognitive Warfare" with Yvonne Masakowski". YouTube. ↑ The Israeli Spokesperson's Unit, which consists of reporters, cameramen, and others in full military uniform, provides news to CNN, Fox News, and other internationally influential media outlets and calls out Hamas's false propaganda as fake. For example, Hamas' photos of alleged refugees in Gaza have been exposed as fake news. ↑ For more information on the events surrounding the flyers - including the condemnation message against the flyers addressed by North Korean leader's sister, Kim Yo-jong, the enactment of the anti-flyer law by the Moon Jae-in government and the ruling party (Article 24 (1) iii of the Inter-Korean Relations Development Act 남북관계발전에 관한 법률), and the Constitutional Court's ruling that the provision is unconstitutional, see Balloon to North Korea. ↑ Yang Wook, a research fellow at the Asan Institute for Policy Studies, said, “South Korea should prepare for North Korea's cognitive warfare by creating a government-level white paper on the background and necessity of the suspension of the inter-Korean military agreement and promoting it through social media.” See supra note 3. ---------- Cognitive warfare is an extension of information warfare (IW).Operations in the information environment are traditionally conducted in five core capabilities - electronic warfare (EW), psychological operations (PSYOPs), military deception (MILDEC), operational security (OPSEC), and computer network operations (CNO).[4] Information warfare aims at controlling the flow of information in support of traditional military objectives, mainly to produce lethal effects on the battlefield. According to Masakowski and NATO Gen Ruggiero, whose statements are cited in the footnotes below, cognitive warfare degrades the capacity to know and produce foreknowledge, transforming the understanding and interpretations of situations by individuals and in the mass consciousness, and has multiple agnostic applications including commercial, political and covert IW and CW military operations. The Chinese military refers to operations in the cognitive domain as 'cognitive domain operations (CDO, 认知疆域操作)'. Meanwhile, cyberwarfare (사이버전쟁/網上戰爭) is the use of cyber attacks against an enemy state, causing comparable harm to actual warfare and/or disrupting vital computer systems. Many countries, including the United States, United Kingdom, Russia, China, Israel, Iran, and North Korea, have active cyber capabilities for offensive and defensive operations. As states explore the use of cyber operations and combine capabilities, the likelihood of physical confrontation and violence playing out as a result of, or part of, a cyber operation is increased. Cyberwarfare refers to politically motivated hacking being conducted in the cyberspace between hostile countries. The social and economic infrastructure in Korea is well equipped with advanced information and communications technologies. The national security is more often than not threatened as much by cyberwarfare between the North Korea. It is a form of information warfare sometimes seen as analogous to conventional warfare. ------- https://www.foreignaffairs.com/china/fog-ai The Fog of AI What the Technology Means for Deterrence and War Brett V. Benson and Brett J. Goldstein January 6, 2026 State-aligned groups are already exploring ways to undermine information security through AI-enabled influence operations. One example is GoLaxy, a Chinese company that uses generative AI tools and vast open-source data sets to build detailed psychological profiles of surveilled individuals and deploy, on a large scale, synthetic personas that mimic authentic users. The company’s campaigns often entail gathering detailed information on influential figures, using that information to produce messages that are likely to persuade targeted audiences, and then sending those messages from carefully crafted social media personas. By achieving an acute level of precision and amplifying misleading narratives across multiple platforms, such operations can sow confusion, corrode public discourse, and weaken the domestic base that makes deterrent signals credible abroad. GoLaxy’s alignment with Chinese state priorities and its ties to state-linked research institutes and superconducting firms make it a sophisticated propaganda engine. Documents we analyzed at the Vanderbilt University Institute of National Security show that GoLaxy has already carried out operations in Hong Kong and Taiwan and has been assembling dossiers on members of the U.S. Congress as well as public figures around the world. Open-source intelligence allows adversaries to build comprehensive dossiers on politicians, military leaders, and soldiers for strategic purposes. Precisely targeted persona operations can then use that information. To score tactical wins, for instance, adversaries could target soldiers with deepfake messages containing false impressions of battlefield conditions or circumstances at home—and including accurate personal details about those soldiers’ lives could make the fabrications seem realistic enough to distract their attention or disrupt unit cohesion. In the political sphere, adversaries could blend real photographs of politicians with cloned voices or faces. Even if they are never released, the threat of their exposure could dampen targets’ rhetoric, stall legislative procedures, or weaken leaders’ resolve. And from a strategic standpoint, hostile parties could simulate authorities giving false orders to stand down or divert to alternative communication channels, which could open a window for an adversary to gain ground. The result is a cognitive fog of war. -------- https://www.orangecyberdefense.com/no/news/orange-cyberdefense/security-navigator-2025-reveals-europe-as-top-target-for-hacktivism Security Navigator 2025 reveals Europe as top target for hacktivism, with groups shifting focus to cognitive warfare 5 December 2024 News Orange Cyberdefense Press Release Hugues Foulon, CEO of Orange Cyberdefense, stated, “Cyber threats have become a critical barometer for anticipating global geopolitical tensions. The insights generated by our cyber teams provide a fresh and robust perspective on international disruptions and their operational impacts on society.” “The Security Navigator 2025 underscores an urgent need for coordinated defensive strategies across Europe and beyond, including enhanced incident response measures, strengthened OT protections, and proactive monitoring of public channels to counter the unique blend of cyber extortion, hacktivism, and cognitive warfare facing European organizations,” said Foulon. ---- On the defensive side, the report found that AI is beneficial for detecting hard-to-identify threats. AI-driven systems have improved detection rates for advanced threats like ‘beaconing’ – a tactic where malware sends subtle, periodic signals to command-and-control servers – reducing incident response times by up to 30% as organizations use AI to identify and intercept these signals before damage can escalate​. However, the report also warns about vulnerabilities in GenAI solutions and urges business to implement strict access rights to sensitive data and systems, ensure isolation between tenants, and educate users about the risk of data leaks in prompts. Charl van der Walt, Head of Security Research at Orange Cyberdefense, said, “The story in this year’s report is far bigger than statistics and technical details. It shines a light on a growing cynicism in the threat landscape as different threat actors seem less concerned about the potential of causing harm, and may even be more intent on inflicting it than ever before.” ---- https://en.wikipedia.org/wiki/Psychological_warfare Psychological warfare (PSYWAR), or the basic aspects of modern psychological operations (PSYOP), has been known by many other names or terms, including Military Information Support Operations (MISO), political warfare, "winning hearts and minds", and propaganda.[1][2] The term is used "to denote any action which is practiced mainly by psychological methods with the aim of evoking a planned psychological reaction in other people".[3] Various techniques are used, and are aimed at influencing a target audience's value system, belief system, emotions, motives, reasoning, or behavior. It is used to induce confessions or reinforce attitudes and behaviors favorable to the originator's objectives, and are sometimes combined with black operations or false flag tactics. It is also used to destroy the morale of enemies through tactics that aim to depress troops' psychological states.[4][5] Target audiences can be governments, organizations, groups, and individuals, and is not just limited to soldiers. Civilians of foreign territories can also be targeted by technology and media so as to cause an effect on the government of their country.[6] Stories are said to be a key factor in a successful operation.[7] Mass communication such as radio allows for direct communication with an enemy populace, and therefore has been used in many efforts. Social media channels and the internet allow for campaigns of disinformation and misinformation performed by agents anywhere in the world ----------- https://en.wikipedia.org/wiki/Private_intelligence_agency A private intelligence agency (PIA) is a private sector (non-governmental) or quasi-non-government organization devoted to the collection, analysis, and exploitation of information, through the evaluation of public sources (OSINT or Open Source INTelligence) and cooperation with other institutions.[1] Some private intelligence agencies obtain information deceptively or through on-the-ground activities for clients.[2][3][4][5][6] Private agencies have made their services available to governments as well as individual consumers; they have also sold their services to large corporations with an interest or investment in the category (e.g. crime, disease, corruption, etc.) or the region (e.g. Middle East, Vietnam, Prague, etc.) or to investigate perceived threats such as environmental groups or human rights groups.[7][8][9][10][11] Some private intelligence agencies use online perception management,[12] social media influencing/manipulation campaigns, strategic disinformation[13] (such as fake news production/propaganda production[14]), opposition research and political campaigns using social media and artificial intelligence such as Psy-Group, Cambridge Analytica and Black Cube.[15][16][17][18][19] The Atlantic Council's Digital Forensic Research Lab described the activity of Archimedes Group as practicing "information warfare".[20] Former anti-corruption prosecutor Aaron Sayne said private intelligence is "an industry that's largely undocumented and has very flexible ethical norms" as agencies collect and use sensitive information "for one purpose on day one and some completely contradictory purpose on day two".[21] The private intelligence industry has boomed due to shifts in how the U.S. government is conducting espionage in the war on terror. Some $56 billion (USD) or 70% of the $80 billion national intelligence budget of the United States was in 2013 earmarked for the private sector according to The New York Times' Tim Shorrock. Functions previously performed by the Central Intelligence Agency (CIA), National Security Agency (NSA), and other intelligence agencies are now outsourced to private intelligence corporations.[22] ---------- https://www.sipri.org/yearbook/2023/04 4. Private military and security companies in armed conflict Contents Overview, Ori Swed, Marina Caparini and Sorcha Macleod (PDF) I. The global growth of private military and security companies: Trends, actors and issues of concern, Ori Swed (PDF) II. Private military and security companies in sub-Saharan Africa, Marina Caparini (PDF) III. The current regulatory landscape for private military and security companies, Sorcha Macleod (PDF) Trends, actors and issues of concern The past 20 years have witnessed the rapid growth of private military and security companies (PMSCs). There is no universally accepted, legally binding, standard definition of a PMSC and the sector often operates in a legal lacuna:the employees of PMSCs are not soldiers or civilians, nor can they usually be defined as mercenaries. The wars in Iraq (2003–11) and Afghanistan (2001–21) reshaped perceptions of the private military and security industry, with the massive deployment of contractors by the United States leading to new market opportunities across the globe. Factors contributing to the growth of PMSCs vary by region and state, but they mostly fit with cost-efficiency calculations, where the sector provides skills and services that states do not possess or that would be too costly for states to develop or perform themselves. Today, PMSCs operate in almost every country in the world, for a broad variety of clients, assuming responsibilities for critical state and security functions. The main actors in the sector include both the host countries in which PMSCs are head-quartered and key companies within those countries. A handful of home states host the majority of PMSCs: the USA, the United Kingdom, China and South Africa together are estimated to host about 70 per cent of the entire sector. Russia, while having a relatively small PMSC sector, has arguably used its contractors for combat more than other countries. There are thousands of PMSCs around the world, most of which abide by the law, operate within their mandate and, in general, contribute to stabilization and security in the settings where they operate, often working closely with the United Nations and non-governmental organizations. In the past two decades, however, the rising prominence of several high-profile PMSCs in conflict areas and security settings has prompted increased public interest in the industry. The Wagner Group Russian private military and security companies have been deployed in combat roles in Libya, Syria and Ukraine, as well as in several conflicts across sub-Saharan Africa. Concerns have centred on the activities of the Wagner Group, effectively a Russian state proxy. The Wagner Group’s activities have been linked with human rights abuses, violations of international humanitarian law, problematic and exploitative contracts, and election meddling. In Mali alone, over 450 civilians were killed in nine incidents linked to the Wagner Group in 2020–22. In Ukraine, the Wagner Group has been deployed en masse alongside Russian military units and it has redeployed operators from other conflicts and recruited nationals from Afghanistan, Libya and Syria. Private military and security companies in sub-Saharan Africa Recent trends concerning PMSC involvement in sub-Saharan Africa suggest that the ascendant actors have close, symbiotic links to home state interests as instruments of national policy and geopolitical competition. Russia and China appear to be driving the current expansion of PMSC activity in Africa, although earlier waves of activity were led by European former colonial powers or were part of cold war proxy rivalries. The current phase of growing PMSC involvement in Africa has occurred in a context of increased geopolitical rivalry and internationalized armed conflict. The control and extraction of natural resources is a common focal point. Western PMSCs remain active in Africa, especially in various counter-terrorism initiatives, but not in direct combat roles. In contrast, Russian PMSCs, in particular the Wagner Group, engage directly in military operations, typically for governments (and currently juntas or military transition governments) threatened by rebels or insurgents, with payment often in high-value natural resources or mining concessions. The Wagner Group has been the focus of numerous UN reports or investigations for alleged human rights abuses and violations of international humanitarian law in sub-Saharan Africa. Chinese PMSCs have emerged more slowly and in a more restrained and circumscribed manner, but with a close connection to Chinese investment, infrastructure development and trade expansion. This may portend a more lasting engagement for Chinese interests and actors, including PMSCs, and a greater strategic impact on access to natural resources and, more broadly, sub-Saharan African political dynamics. --------- The current regulatory landscape While the use of PMSCs in armed conflicts and fragile environments appears to be growing, questions remain about the adequacy of existing inter-national efforts and norms to regulate the sector. One of the key regulatory challenges is the use of PMSCs, particularly by Russia and Türkiye, as proxy actors in armed conflicts. These deployments are often framed as lying outside the international legal definition of a mercenary, so some states have turned to counterterrorism approaches instead, for example, by seeking to impose terrorist designations on the Wagner Group or by sanctioning its leading personnel. Cases attempting to hold mercenaries and PMSC personnel to account under criminal justice regimes are rare. Regulatory endeavours at the UN have been reinvigorated by the war in Ukraine and the activities of the Wagner Group. A UN intergovernmental working group process has been attempting to address the gaps between the international legal provisions addressing mercenaries and the softer regulatory approaches of multistakeholder initiatives addressing PMSCs, such as the Montreux Document and the International Code of Conduct for Private Security Providers. However, consensus on the necessity of a legally binding instrument, let alone substantive content, remains elusive. Several key issues arose in the working group discussions in 2022: states were still unable to agree on whether the instrument should be binding or non-binding and there was lack of consensus on its scope, human rights provisions and the content on accountability and remedies for victims. Discussions will continue at the UN in 2023, but whether they will translate into concrete and credible regulatory change remains to be seen. Dr Ori Swed, Dr Marina Caparini and Dr Sorcha MacLeod ------- https://www.vojenskerozhledy.cz/en/kategorie-clanku/bezpecnostni-prostredi/19777-issues-of-resilience-to-cyber-enabled-psychological-and-information-operations Issues of Resilience to Cyber-Enabled Psychological and Information Operations Created by Alias: Mlejnková Petra This article discusses the transformation of the information environment, which allows an adversary to exploit cyber-enabled psychological and information operations. It presents the options currently available to an adversary to exploit the vulnerability of the information environment, chiefly the cognitive vulnerabilities of target groups. Thus, hostile interests are often pursued through manipulation, using disinformation, propaganda, algorithms and artificial intelligence. In the light of these developments, the article defines a society-centric approach, in which societal and human resilience are emphasised. -------- https://academic.oup.com/sleep/article/44/7/zsab008/6092754 The effect of sleep restriction on cognitive performance in elite cognitive performers: a systematic review Open Access Tim D Smithies , Adam J Toth , Ian C Dunican , John A Caldwell , Magdalena Kowal , Mark J Campbell Sleep, Volume 44, Issue 7, July 2021, zsab008, https://doi.org/10.1093/sleep/zsab008 Published: Optimal cognitive functioning is fundamental to performance within many work environments. In select safety-critical occupations, the ability to perform complex, cognitively demanding tasks within unpredictable circumstances is integral to operational success. Active military personnel [1], aviation pilots [2], air traffic controllers [3], emergency responders [4], surgeons and medical practitioners [5, 6], and process operators in potentially dangerous environments (i.e. mines, power plants, oil refineries) [7] are all examples of individuals involved in such safety-critical professions. Additionally, while elite athletes do not engage in safety-critical work, optimal cognitive functioning (i.e. attention, executive functioning, decision making) within time-constrained and unpredictable environments is often integral for elite performance [8, 9]. Individuals within these professions must exhibit cognitive expertise not normally present within the general population for operational success, given the complexities and cognitive demands embedded within the tasks involved. Individuals in some of the professions mentioned (i.e. athletes, pilots, air traffic controllers) have been shown to demonstrate enhanced cognitive performance compared to the general population not only within the context of their area of expertise, but also through laboratory testing [10–13], though see an article for Taylor and colleagues [14] for a contrary finding, particularly during task-switching, multitasking and attentionally demanding task paradigms. As a result of the aforementioned cognitive demands and the observed performance benefits these individuals may possess, we refer to them here collectively as Elite Cognitive Performers (ECPs). -------- Sleep quantity has been identified as a key moderator of cognitive performance [15–18]. To date, most sleep quantity research has concerned itself with total sleep deprivation (TSD; a total elimination of sleep obtained during a specified time period), primarily due to the time and cost efficiency of their designs [19]. However, TSD is uncommon ecologically, whereas sleep restriction (SR), referring to a moderate reduction in the amount of sleep across one or more nights (~2–6 h sleep obtained per night), is far more commonly experienced both by the general population [19] and by ECPs [20, 21]. The fact that SR is more frequently experienced than TSD, and that each affects human neurobiology differently [19], has led more recent work to specifically focus on understanding the effects of SR on cognitive performance. In addition to the reviews assessing the effects of SR on cognitive performance among youth [22] and adolescent [23] populations, experimental sleep dose–response studies, such as those conducted by Belenky et al. [24], Jewett et al. [25], Van Dongen et al. [26], and Banks et al. [27], have provided comprehensive insight into the effects of SR on cognition. The results of studies such as by Belenky et al. [24] and by Van Dongen et al. [26], as well as other experimental research, have informed the creation of biomathematical fatigue models, used in safety-critical environments to identify periods of risk and, guide mitigation, and maximize performance [28]. Recently, Lowe et al. [17], in a meta-analysis investigating the effects of SR on cognitive performance, found SR to impact “sustained attention” tasks more than increasingly complex tasks assessing performance in other cognitive domains across numerous populations and age groups. This finding corroborates those of Wickens et al. [29], who noted that simple cognitive task performance is more greatly impacted by sleep loss, as well as earlier seminal research outlining the comparatively greater effects of sleep loss on simple tasks [30]. ---------- That performance on simple tasks appears selectively hindered by SR initially seems counter-intuitive, as prefrontal cortex (PFC; integral to executive functioning) activation is decreased by sleep loss [31, 32]. However, imaging studies (using functional magnetic resonance imaging) have found strong evidence for increased recruitment of frontostriatal circuits and additional brain areas coinciding with the maintenance of performance during increasingly complex and engaging cognitive tests despite decreased PFC activation [31, 33–36]. Through this lens, simple attentional test performance tends not to receive similar compensation due to a lack of arousal, stemming from the low stimulus/salience nature of such tests [37, 38]. Recent work has suggested that these compensatory mechanisms function in a way so as to give preference to task information already present within working memory, helping to maintain focus and attentional strategy throughout the task (i.e. cognitive stability). However, the trade-off appears to be that the ability to alter this information within working memory (i.e. cognitive flexibility), necessary for when attention needs to be shifted when a task dynamic changes (as is common within real-world tasks), is impeded [38]. Despite the abovementioned literature outlining the effects of SR among general populations, it is less clear how SR affects the cognitive performance of ECPs or whether this group is differentially affected by SR. The importance of studying this group independently from the general population is three-fold. Firstly, optimal cognitive performance is arguably more important for ECPs than for the general population, as errors or inadequate performance can have critical outcomes, ranging from loss of competition for high-level athletes, to loss of life in safety-critical occupations. Numerous high-profile catastrophes have involved human errors linked to sleep loss, such as the fatal decision to launch the Space Shuttle Challenger in 1986. In the report on the Presidential Commission on the Space Shuttle Challenger Accident [39], it was stated that prior to an important teleconference regarding the decision to launch (a decision proving to result in seven casualties), “key managers obtained only minimal sleep the night before the teleconference” (p. G5), which may have led to poor judgement contributing to the fatal decision to launch. Another example is the pervasiveness of fatigue in aviation, where it is estimated that fatigue contributes to 4%–8% of aviation catastrophes [40]. Secondly, ECPs are at an increased risk of experiencing SR due to their occupational requirements. For example, sleep opportunity can be sparse and unpredictable throughout military combat operations, while other military-specific stressors, such as watch duty and field-based exercises, result in the frequent occurrence of SR [20]. Commercial pilots often have demanding schedules, are constantly exposed to rapid time-zone changes, and often must obtain night-time sleep in uncomfortable cockpit environments, resulting in regularly experienced SR. Rapidly changing work schedules are common for air traffic controllers, causing drastic reductions in sleep quantity, with some operating with as little as 2 h of sleep at times [41]. Irregular and demanding shift work schedules can lead to SR for emergency medical practitioners [42]. Finally, elite athletes can experience SR due to the timing and intensity of training and competition schedules, as well as air-travel requirements, especially when traveling over multiple time-zones [43]. --------- Thirdly, contemporary literature has suggested that ECPs at a group level may demonstrate increased resistance to the effects of sleep loss on cognitive performance. For example, one study found a group of seven active-duty F117 fighter pilots to have greater baseline global cortical activation compared to nonpilots during a working memory task, which then positively correlated with performance on a flight simulator task after 37 h of TSD [44]; however, the authors advocated for further research on larger samples to validate such a finding. In reference to this, some authors have discussed the idea that naturally tolerant individuals to sleep loss may either “self-select” into, or that vulnerable individuals may “self-select” out of, active military professions due to the necessity of maintaining performance following sleep loss [21, 45, 46]. Similar theories have been posited to explain a lack of performance degradation following sleep loss among medical residents [47, 48]. It is noted that individual differences in tolerance to sleep loss within elite groups such as the U.S. Air Force are still present [49]. Together, the importance of optimal cognitive performance for ECPs, their increased risk toward experiencing SR, and their potential increased tolerance to the performance effects of SR at a group level, all make the study of the effects of SR on cognitive performance in ECPs worthwhile. To date, no attempt has been made to review the existing literature examining the effects of SR on the cognitive performance of ECPs. As a result, the purpose of this review is to synthesize and summarize the existing literature explicitly examining the effect of SR on cognitive and occupation-specific performance among ECPs. ------ Database search strategy This review was not registered prior to its undertaking. Included articles did not have to be published in peer-review scientific journals to be considered. Articles included for the current review were obtained through an exhaustive systematic search, in accordance with the updated PRISMA guidelines [50]. Embase, MEDLINE (Ovid MEDLINE(R) and ePub ahead of print, in-process & other nonindexed citations, daily and versions(R)), Web of Science (Core Collection), and Google Scholar databases were searched, as the combination of these four databases presents superior sensitivity/specificity trade-off for systematic searches [51]. Subject-specific databases APA, PSYCinfo, and SportDiscus (both EBSCO host) were also queried to add further sensitivity to the search. Searches using these databases took place on January 27, 2020, except for Google Scholar, which took place the next day. The exact syntax used for each primary database can be found as supplementary file 1. The search strategy for each database involved identifying “key-words” (22 total) within titles and abstracts pertaining to the motor or cognitive abilities, or performance, and combining them with words pertaining to SR (five total), with the exclusion of words related to animal studies, clinical conditions, or reviews. Controlled vocabulary terms (MeSH/EMTREE) were explored and used as exploded terms (searching for the particular word as well as the more specific words that stem from it within the given organization system) where relevant in databases that allowed for them. Inbuilt database filters were used where available to remove studies specifically investigating nonhuman subjects, children, or the elderly; no date or language restrictions were enforced. TS performed the search and screening described. All identified article references were extracted and exported into Endnote version 9.2 (Clarivate Analytics), except for those found via Google Scholar, where only the first 200 references (when searched by relevance; as per Bramer, Rethlefsen, Kleijnen, Franco [51]) were extracted. Overall, 4,648 articles were identified through this search process, with 2,421 remaining once duplicates had been removed (see Figure 1). --------- Gray literature and backward snowballing As some research concerning the effects of SR on performance among ECPs may not have been detected by the above database searches, an additional gray literature search was performed in addition to the use of “backward snowballing” techniques. Five sources of grey literature were queried; two conventional search engines (Google, duckduckgo), two gray literature specific databases (OpenGrey and Science.gov), and the Defence Technical Information Centre (DTIC). These searches took place between January 31, 2020 and February 4, 2020. For these searches, similar terms to those used in the primary database searches were used (see supplementary file 2 for the exact syntax used for each grey literature database search). For the DTIC search, the first 100 results were investigated, while for the other grey literature sources, the first 50 were investigated (or less, if less than 50 results appeared), in a similar fashion to that discussed for Google Scholar by Bramer et al. [51]. “Backward snowballing” refers to a technique where the reference lists of previously identified reviews or journal articles within a relevant topic are searched to obtain further relevant articles [52]. Due to prior knowledge that many studies conducted in defence institutes are not published in peer-reviewed journals and are therefore not identified by primary database searches, reviews focusing on such studies were targeted for backward snowballing. Additionally, the references of two reviews on the effects of SR on cognition in the general population were also searched, as they were considered to be the closest in content to the current review. Overall, the reference sections of five reviews and one annotated bibliography were searched for relevant studies [17, 29, 53–56]. Backward snowballing was manually performed by TS. In total, 264 articles identified based on their title and abstract through the grey literature searches, and 577 articles identified through backward snowballing were screened (Figure 1). ========== The authors would like to thank Niall Ramsbottom, who assisted in the coding of training effect bias in the current review. 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