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Work 47 (2014) 387–397 DOI 10.3233/WOR-131771 IOS Press

Evolutionary adaptations: Theoretical and practical implications for visual ergonomics Knut Inge Fostervolda,∗, Reidulf G. Wattenb and Frode Voldenc a

Department of Psychology, University of Oslo, Oslo, Norway Lillehammer University College, Lillehammer, Norway c Gjøvik University College, Gjøvik, Norway b

Received 30 November 2012 Accepted 15 April 2013

Abstract. BACKGROUND: The literature discussing visual ergonomics often mention that human vision is adapted to light emitted by the sun. However, theoretical and practical implications of this viewpoint is seldom discussed or taken into account. OBJECTIVE: The paper discusses some of the main theoretical implications of an evolutionary approach to visual ergonomics. DISCUSSION: Based on interactional theory and ideas from ecological psychology an evolutionary stress model is proposed as a theoretical framework for future research in ergonomics and human factors. The model stresses the importance of developing work environments that fits with our evolutionary adaptations. In accordance with evolutionary psychology, the environment of evolutionary adaptedness (EEA) and evolutionarily-novel environments (EN) are used as key concepts. Using work with visual display units (VDU) as an example, the paper discusses how this knowledge can be utilized in an ergonomic analysis of risk factors in the work environment. CONCLUSION: The paper emphasises the importance of incorporating evolutionary theory in the field of ergonomics. Further, the paper encourages scientific practices that further our understanding of any phenomena beyond the borders of traditional proximal explanations. Keywords: Visual ecology, human nature, environment, evolution, visual display unit (VDU)

1. Introduction The importance of visual ergonomics has increased rapidly with the rise in white-collar jobs and the extensive use of Visual Display Units (VDU). Today the number of office workers has surpassed those employed in industrial production in many western countries. Although the development of VDUs has propelled the interest in visual ergonomics, potential health hazards ascribed to intensive visual work is not confined to modern work-life. In 1713, Bernardino Ra∗ Corresponding author: Knut Inge Fostervold, Department of Psychology, University of Oslo, P.O.Box 1094, Blindern, N-0317 Oslo, Norway. Tel.: +47 22 84 50 57; E-mail: k.i.fostervold@ psykologi.uio.no.

mazzini [1] wrote his influential treatise “De Morbis Artificatum Diatriba” (Diseases of workers) were he vividly and insightfully described the sufferings of different occupational groups in the Modenese territories in Italy. Among the illnesses and problems described are those that sedentary workers, people engaged in intensive and prolonged near-work, and “learned men” suffer from. In most cases, Ramazzini [1] assumed work-related visual problems to be functional and behavioural in origin. Although the understanding of anatomy and physiology was limited at that time, his holistic approach was progressive and remarkable similar to conceptions found in the literature today. Looking at contemporary literature, a variety of environmental and job related factors have been ascribed to affect vision, visual stress and visual ail-

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ments. Among the more frequently discussed factors are a diversity of air pollutants, the amount of near work, visual quality, glare and inappropriate lighting, electromagnetic fields, job demands, job quality, social support, minor visual errors, and unsuitable visual corrections [2–12]. Not infrequently, references are made to human ecology and the evolutionary basis for vision [13–16]. The main notion seems to be that light, or more precisely electromagnetic radiation with a wavelength between 400 and 700 nanometres, has been a decisive environmental factor in the evolution of mankind. In our original habitat sunlight was the only real source of light available when important activities were to be carried out. Consequently, man has developed a sensory system and a rhythm of life adapted to this source of light. In some cases, evolutionary viewpoints have provided the basis for speculations and hypothesis about cause and effect relationships. Within lighting research for example, claims have been made about beneficial effects achieved by the use of specific light sources, lighting systems, and coloured filters [16]. The effect of full-spectrum artificial lighting has gained much interest as it has been assumed to mimic significant aspects of sunlight. Research along this line of thought has revealed that a colour spectrum close to daylight causes better regulation of the pupil opening, as opposed to warmer colours, and that increased colour rendering results in a general feeling of seeing better [17]. However, thorough reviews of the literature do not show any dramatic effects of fluorescent lighting on behaviour or health compared to other artificial lighting systems [18–20]. The discovery of non-visual photoreceptors in the eye has encouraged a new and promising field of research in this regard. The photoreceptors have been connected to the circadian regulation of sleep and wakefulness through the secretion of Melatonin and Cortisol [21]. Based on this finding dynamic lighting systems have been suggested that is dynamic both with regard to lighting level and the tint of whiteness of the lighting colour. The idea is that a closer resemblance to the dynamic changes of natural lighting conditions will affect sleep and wakefulness and thereby influence health and well-being [14, 22]. However, thus far, it has been difficult to demonstrate clear benefits from interventions following this line of thought [15], although recent research may suggest that increased levels of ambient lighting in classrooms may affect student achievement in a positive direction [23]. Considering the present situation, reflections about human evolution and evolutionary adaptations do not

seem to be the master key to viable understanding of visual risk factors in modern work-life. Without sounding flippant, it is possible to argue that evolutionary statements represent nothing more than empty phrases or anecdotes. This notwithstanding, a common feature in most ergonomic literature referring to evolutionary considerations is that the concept of evolution itself is rarely discussed. Neither is the implications extensively elaborated. Thus, the problem might not be that analyses of evolutionary adaptations are theoretically or practically deficient, but that the evolutionary viewpoint is poorly understood and applied in the ergonomic literature. The aim of the present paper is to present an overview and discuss some of the basic concepts and theoretical implications of an evolutionary approach to visual ergonomics and provide examples of how this perspective can be utilized both in research and in practical work. Work with Visual Display Units (VDU) is used as an example throughout this paper, but the theoretical principles discussed are not confined to this work situation and should be applicable both in other areas of visual ergonomics and in ergonomics in general.

2. Theoretical considerations 2.1. The traditional medical model Although not always made explicit, the majority of traditional ergonomic research seems to have been accomplished within the framework of traditional medical and biomechanical models, in which the notion of the dose – response relationship is essential. Owing to this tradition, discomfort and health problems related to work have been understood in terms of simple cause and effect relationships between environmental factors and specific symptoms. Using VDU work as an example, visual problems have been linked to inferior visual quality of the VDUs, while musculoskeletal problems primarily have been regarded as a result of inferior office furniture and incorrect sitting posture. However, few evaluation studies have been conducted to verify ergonomic optimisation according to this theoretical framework, and among those that exist, several have shown unsuccessful [24–27]. Several explanations may exist for this lack of improvement. Winkel and Westgaard [26] point to the fact that much ergonomic work omits the basic source of

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problems in VDU-work, the design of production systems. Another possibility resides in the non-specific nature of most visual ailments. Most ailments are quite common, exist across a variety of working and living conditions, and may be caused by very different environmental exposures, as well as individual genetic factors and mental conditions. Thus, in any worker cohort the incidence of visual ailments includes both what we may call public generated complaints and work-related ailments. Depending on the design and the sensitivity of the chosen measures, it is quite likely that the severity of work related visual problems, which the intervention aims to remediate, are not large enough to avoid “drowning” in public generated complaints. Nevertheless, a more fundamental problem may reside in the theoretical basis for much ergonomic research. Surprisingly, little empirical work aimed at identifying risk factors in VDU work and their remediation seems to be theoretically driven. This is neatly exemplified in an overview by Meister [28], showing that only 1% to 2% of all papers published within the field of ergonomics and human factors seek to test a specific theory. The combination of an oblivious use of the traditional medical model and a neglect of theory has encouraged a scientific practise that somewhat disrespectfully may be termed as “plug in ergonomics”. Consequently, traditional ergonomic research is often both monocausal and unidirectional, in that individual work related symptoms are predicted from simple work site conditions or from intrapersonal factors alone. This lop-sidedness permits us merely to draw interference about what design is better but does not provide much information about why it is better. Optimising individual workstation components without knowledge of the mutual influence that different components may have on each other can easily result in an overall outcome that is not only suboptimal, but may in fact result in adverse health outcomes [29]. It is questionable whether an empirical practice based on the assessments of the exposure amplitude of single factors, have the flexibility and theoretical coherence necessary to explain the heterogeneous and often subtle composite of complaints found in the modern work place. 2.2. The interactional perspective Due to theoretical and practical limitations, a growing number of theoretical approaches with an interactional perspective have been developed. Dainoff and Dainoff [30] define the subject matter of ergonomics as “the fit between the human being and those inan-

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imate things, especially machines, with which he or she interacts.” (p. 1). Inherent in the concept of fit is the notion that there is an interactive relationship between the human and the machine. Taken together, the two parts constitute an entity known as the man – machine system. The term system refers to the reciprocity in the relationship between the individual and the machine, where properties of the individual affect properties of the machine and vice versa. Although machines are mentioned specifically, the definition is not literally confined to the relationship between the user and the actual machine. A more accurate definition, that is more in accordance with the complexity of modern work life, would be to rephrase the man – machine system into the person – environment system. In many respects, Lazarus’s [31] writings on psychological stress have had a major influence on this development. Interactional theories are therefore often dominated by person centred constructs like mental load, coping style and cognitive failure. Symptoms in this perspective are seen as each individual’s reaction to the interaction between environmental stressors and intrapersonal condition. Within these models, the heterogeneity in symptomatology constitutes the core in understanding health problems. By accounting for the joint influence of both environmental and intrapersonal factors in the understanding of work related symptoms, the interactional perspective represents a major theoretical advancement. 2.3. The ecological approach and direct perception Influenced by ecological psychology and Gibson’s [32] theory of direct perception, the ecological approach to ergonomics and human factors, emphasise the importance of understanding the goals of the system. According to this approach, the system consists not only of the user and the environment, but also of system goals, i.e., actions performed by the goal directed user. To understand the system and why malfunctions occur, it is necessary to incorporate the goals of the system into the ergonomic analysis [29]. System goals vary considerably between otherwise identical environmental settings. Goal achievement requires a variety of actions. Each action requires a coupling of forces between the user and relevant parts of the work environment. The execution of actions transforms the physical environment and the relationship between the user and the environment. Consequently, the properties of a system can be specified only if the goals of the system are identified.

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The concept of affordance is used to explain the interrelationship between the goal-directed user and the environment [33]. According to Gibson [31], the environment contains invariant information that has survival value for the organism. Affordances is not a property of objects in the environment, neither is affordances properties of the organism. Affordances are seen as a lawful relationship between the sensory apparatus of an organism and a specific environmental setting [29]. The perception of affordances is thus dependent on both the environment and the organism that inhabit the environment. Perceived affordances guide behaviour by telling the observer which actions that are, or are not, possible in a given setting. Within this framework, organisms are perceived as active and explorative. Behaviour in this context is understood as spirals of perception – action loops. Affordances that are perceived by the organism entail possibilities for a range of specific actions. The choice of action transforms environmental properties, which render other possible affordances to be perceived, which, in turn, entails new possibilities for actions [34]. However, within the array of possible actions available, some seem to be preferred more often than others. It is as if some affordances are perceived stronger than others and thereby invoking more attention [35]. To some part, this can be explained by constraints induced by individual capabilities for action. Two classes of constraints have been defined. Personal constraints entail anthropometric constraints (body dimensions) and biodynamic constraints (strength, body mass, etc.). The second class is environmental constraints, which refers to geometrical and physical properties of objects, like size, shapes, surfaces, weight and texture, which will affect the possibility for actions [33]. Obviously, people tend to choose action possibilities that accord with their action capabilities. Nevertheless, this does not explain the full range of preferred actions that are easily observed in everyday life. Sometimes this has been framed as if some affordances invite to behaviour [33]. Although this idea is not in accordance with the original writings of Gibson [32] it is not a suggestion about environmental determinism. Behaviour does not inevitably follow the presence of an affordance that invites to behaviour, but represents an increased likelihood for specific actions if the circumstances are appropriate. Much is still unclear about what patterns in the environment that invite to behaviour, under which circumstances they do so, and why a specific organism is disposed to react in this manner. Culture and personal history have been men-

tioned as possible drivers, but in many respects there seem to be affordances that, at least humans, perceive and react to quite uniformly. It is therefore possible that some affordances represent evolutionary adaptations or predispositions towards environmental properties that increase survival and reproduction [36]. To conclude this section, the ecological approach offers a theoretical explanation for- and a tool to analyse the systemic relations that exist between the user, the work environment, and the actions that are being performed at the workplace. By so doing, the ecological approach makes a crucial contribution to interactional theory.

3. An evolutionary approach Although the ecological approach is grounded in evolutionary thinking [33,36] this approach, as well as the traditional medical model, mostly address proximate causes in their analysis of health, perception, and behaviour. Proximate explanations primarily address questions concerning how the body works. For example, why some people develop symptoms and diseases while others do not, how people perceive objects and movement in a three-dimensional world, and how behaviours are triggered, performed, and learned. Proximate explanation describes structures, mechanisms and processes in the body, by means of anatomy, physiology, biochemistry, and cognition, as well as its ontogenetic development, in their effort to understand the occurrence of symptoms and disease, abnormal behaviour, human error, and distorted perception [37– 39]. In research, proximate explanations seldom address questions about the origin and functional development of structures, mechanisms and processes. Evolutionary explanations, on the other hand, address ultimate causation [38,40]. The try to understand why the human species are prone to develop specific diseases and why some body parts are developed to tolerate high amounts of strain while others develop malfunctions quite easily. To develop a comprehensive understanding of malfunctions, diseases, and symptoms associated with visual work, which can guide research and practice, it is necessary to incorporate answers to such questions into the realm of theory construction in ergonomics and human factors. A promising alternative in this regard is to combine the ecological approach with knowledge and analysis of evolutionary adaptations. The amount of literature discussion evolutionary theory and its application within different fields is vast.

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Owing to the seminal writings of John Tooby and Leda Cosmides [41,42], the development of evolutionary viewpoints in theory and research has been especially pronounced in psychology. The ultimate goal, of what has been coined evolutionary psychology, is to understand the evolutionary basis for psychological phenomena such as the development of the human mind and symbol based language. The present account is inspired by evolutionary psychology and borrows parts of its conceptual framework from this tradition. 3.1. The environment of evolutionary adaptedness According to the ecological approach to visual perception, it is necessary to view the environment and the animal as inextricable connected interacting systems. Animals cannot exist without being surrounded by a specific environment and a specific environment implies an organism to be surrounded [32]. Thus, in order to understand the consequences of visual work in modern work life, it is necessary to consider the environment of evolutionary adaptedness (EEA). EEA is a key concept in evolutionary psychology and designates the ecological niche in which a specific set of adaptations is adapted [41,42]. In our context the term refers to the environmental conditions that have moulded the human perceptual system and in which visual work has evolved. The environment of evolutionary adaptedness is usually placed on the African savannah during Pleistocene, approximately 50,000 years ago [43], However, Tooby and Cosmides [41,42] are quite clear in that the EEA does not refer to a specific place in time. The term should instead be understood as a summary or statistical composite of specific environmental properties that characterize the environment in which current adaptations found their final form. Thus, different evolutionary adaptations could, and probably have, different EEAs. The notion of EEA as a crucial element in the understanding of the development and functionality of evolutionary adaptations has been questioned. Among the issues raised are the speed at which evolution takes place, the importance of epigenetic factors, and the amount of interpopulational genetic diversity that is needed to assume new evolutionary adaptations [43, 44]. Nevertheless, there seems to be little evidence indicating that the basic properties of the human perceptual and visual system differ significantly between populations or has changed notably since Homo sapiens migrated out of Africa.

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3.2. Evolutionarily-novel environments Evolutionarily-novel environments (EN) are another important construct in an evolutionary approach to visual ergonomics. Characterising an environment as evolutionarily-novel (EN) entails claims both about the environment and about the species that inhabit the environment. As to the environment, the term implies that the current environment differ from the environment of evolutionary adaptedness (EEA), at least for one significant aspect. For the species, the term implies that a significant change has occurred in an environmental aspect for which the species has developed specific phenotypic adaptations [45,46]. From this it follows that not all new environments automatically are to be considered as evolutionarilynovel. The key element is whether or not specific evolutionary adaptations in a specific species, are associated with specific environmental properties that have been notably changed, or are no longer present, in the current environment. 3.3. An evolutionary stress model As far as evolution is concerned, man is still adapted to the conditions of our foraging ancestors. Human capabilities and limitations are therefore closely connected with our natural habitat. Despite the fact that human functions have evolved with reference to society’s earlier stages, history reveals that man as a species has an almost unlimited adaptability, based on intellectual skills and the ability to learn. Dazzled by this recognition, there is a danger of ignoring the costs of extended adaptation to living conditions peripheral to the environment of evolutionary adaptedness (EEA). Instead of interpreting lacking adaptability as a sign of limitations specific to the species, it is often interpreted as sign of individual weakness. In this context, negative health development could be interpreted as a mismatch between limitations in adaptability and coping demands in a particular environment. Acknowledging the reciprocity between human capabilities and the environment in which the species has evolved, health problems or human error may be explained in terms of an evolutionary stress model. In this model, stress is seen as the net product of specific coping demands and the ecological fit between individual coping ability and the degree to which a given environment corresponds with the EEA. The term ecological fit is used to accentuate its evolutionary basis, which is somewhat different from the meaning usually assigned to the construct

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Fig. 1. Schematic representation of an evolutionary stress model. (A) Coping is maintained without major costs. (B) Coping implies compensatory activities with increasing risk of negative consequences. (C) Coping implies massive compensation with impending danger of health hazard. (1) Individual upper limit for coping not requiring compensatory activities. (2) Individual upper limit for coping. (3) Individual critical load limit for the transition from negative consequences to impending health hazard. (Colours are visible in the online version of the article; http://dx.doi.org/10.3233/WOR-131771)

person – environment fit. A simplified representation of this model is shown in Fig. 1. According to this model, interaction with the environment is mastered without major costs, if the environmental demands correspond to capabilities developed through evolution. Under such circumstances the person – environment interaction could be characterized as entailing good ecological fit. Reduced correspondence, or reduced ecological fit, reduces the ability to cope as well, and consequently the need for compensatory activities increases. To a certain extent, compensatory behaviour may maintain the coping ability of the individual without obvious negative consequences. However, if humans are forced to operate in habitats that push the limits of those capabilities, sustained coping may engender negative consequences. The manifestation of such effects is best characterised as the interaction between an individual’s environment and their psychological and physiological adaptations. It must be expected that this person– environment interaction also entail large interindividual differences. People not only vary with regard to coping limit, they also vary on genetically based personality characteristics, learned coping strategies, and vulnerability to psychological and physical strain, to mention a few. It is also a reasonable assumption that subclinical remnants from coping efforts that do not manifest as symptoms or human error may still be present. Over years, such remnants may accumulate and result in long-term effects. It is therefore important to emphasize that the risk factors involved in the person – environment interaction do not provide a ba-

sis for predictions about individual health trajectories. The evolutionary stress model consequently implies that statements about cause and effect, based solely on observed symptoms, become untenable. Although the evolutionary stress model renders the traditional dose – response model invalid, analysis of evolutionary adaptations and ecological fit represents an analytical tool that may guide theory building, development of novel research questions and testable hypothesis. The following sections provide examples of how this can be done, using work with visual display units (VDU) as an example.

4. The evolutionary stress model and the VDU workplace Evolutionarily-novel environments (EN) constitute a central element in the understanding of ecological fit. A decisive question is consequently whether the environmental aspect in question can be regarded as evolutionarily-novel (EN). If so, it follows from the stress model that the environment entails reduced ecological fit and thereby poses increased probability of negative health development and an increased probability of human error. 4.1. When new environments are not evolutionary novel Exposure to electrical fields surrounding VDUs has for many years been discussed as a potential health

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risk. A variety of symptoms has been mentioned, but among the more frequent are visual and ocular symptoms, skin symptoms, cataractogenesis, teratogenesis, and hypersensitivity to electricity [4,47–49]. In terms of evolution, electrical fields emanating from computers or other electrical devices seem to be novel and lacking in the EEA specific to the human species. A variety of measures have been developed to remedy problems associated with electrical fields at the workplace ranging from complete renewal of electrical wiring in the office at the extreme end to different types of shielding paints and liquids. Among the different shielding devices developed, VDU screen filters have obtained some popularity and some short term intervention studies have indicated some positive effects [50]. However, long term intervention studies and epidemiological studies do not seem to support these findings [49,51]. Neither has provocation studies been able to establish a link between electric devices and perceived symptoms [52]. On the contrary, research indicate that the divergence between findings obtained in short-term intervention studies and studies using other methodological approaches most likely are caused by participant reactivity [4]. Thus, if electrical fields emanating from VDUs genuinely represent an evolutionarily-novel (EN) environment, the findings obtained do not seem to concur with predictions made from the evolutionary stress model. Nevertheless, electrostatic and electromagnetic radiation is a naturally occurring and an inevitable part of the biosphere. Vision, for example, is in itself an adaptation to electromagnetic radiation. Thus, since the dawn of time exposure to electric radiation, covering a wide range of frequencies and amplitudes, has been an evident parameter of the environment inhabited by the human species. To the extent that naturally occurring electric activity has evolutionary consequences, one should expect that specific phenotypic mechanisms have evolved as an adaptation to that activity. The existence of such adaptations has been demonstrated by Schienle et al. [53]. In the study, they simulated electromagnetic activity similar to that produced prior to thunderstorms; a phenomenon known as atmospherics. In healthy individuals, exposure to atmospherics yielded reduced α-wave activity in the brain. Thus, from an evolutionary point of view, one might conclude that phenotypic adaptations to atmospherics have increased the survival rate of the species [54]. Considering the amount and diversity of naturally occurring electric fields and their phenotypic adapta-

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tions, most newly created artificial fields hardly fulfil the requirements necessary to be regarded an EN environment. As long as the electric fields emanating from VDUs do not interfere- or tamper with adaptations to naturally occurring electrical fields, one should not expect any particular negative effect from their presence. On this background, the obtained results concur with the expectations derived from the evolutionary stress model. This line of argument also applies to the discussion about the consequences of artificial lighting. Acknowledging that all evolutionary adaptations related to illumination are based on parameters present in natural sunlight, it is tempting to argue that artificial lit environments are EN. The common use of artificial lighting in modern workplaces should consequently represent a possible health hazard. However, there are serious doubts about the justifiability of this assumption. It is important to bear in mind that the factors such as the illuminance level, the relationship between light and shadow and the spectral quality of daylight vary considerable both over the course of a day and with shifting weather conditions. Consequently, the visual system has evolved an ingenious mechanism for adapting to differences in lighting conditions. Although, several environmental parameters are involved in the regulation of this adaptation mechanism, the most important are the adaptation luminance in the visual field and the colour spectrum of the light. To exemplify the splendour of the mechanism it suffices to mention that a light level of 500 lux, which is perceived as rather satisfactory indoors, is perceived as dusk outdoors. Thus, the adaptation mechanism of the human eye makes it possible to maintain satisfactory vision under a variety of lighting conditions that includes the variability found in most artificially lit environments. By acknowledging the flexibility of the visual system and its phenotypic adaptation to diversified lighting conditions, it seems untenable to maintain the assertion that artificial lighting represents an EN environment. Therefore, somatic symptoms or behavioural changes should not be expected from manipulating the light so long as it is conducive to the work being done. Thus, the conclusions from literature reviews, indicating that full-spectrum fluorescent lighting does not yield improved health compared to other artificial light sources concur with this expectation [18, 19,24]. 4.2. When new environments are evolutionary novel In the beginning of the nineteen eighties, reports about adverse health reactions among VDU-workers

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started to appear [55–57]. Although potential health hazards ascribed to intensive near-work already had been subject to debate for many centuries [1], the introduction of VDUs was assumed to represent a new health hazard in the work environment, with a potential of being more harmful than previous near-work. Although still under debate, reviews of the literature seems to support this impression by indicating a somewhat higher prevalence of complaints among VDU workers compared to employees not involved in VDU work [48,51]. When comparing VDU users with nonusers, it is important to bear in mind that the two populations do not only differ with respect to the use of VDUs. Further, it is well known that a range of organisational and job specific changes normally accompany the introduction of VDUs [58]. One might therefore question whether the two populations are comparable methodologically. On this backdrop, it is pertinent to ask whether VDU work is substantially different from other kinds of nearwork. If that seems to be the case, the succeeding questions would be why VDU work is different and in what respect VDU work is different from other traditional forms of near-work. At the most general level of analysis, it is important to note that near-work hardly can be regarded as an EN environment, as it obviously has been part of the long-term historic behavioural repertoire of the human species. At a specific level, however, this is necessarily not so. VDU work comprises a variety of different factors and it may be that some of these factors are outside the range of long-term historic variation, although near-work in itself is not. If such factors counteract phenothypical adaptations to ecological near-work they would represent a potential source for negative health development. Thus, to enhance the understanding of factors in VDU work that affect health and behaviour, it may provide useful to achieve a better insight into the environment of evolutionary adaptations (EEA) in which near-work has evolved. In an attempt to do so, an evolutionary analysis of near-work has been set forth, emphasising the relationship between environmental factors characterising the near-work situation, visual nearpoint stress and nearwork related symptoms [6,59,60]. According to this analysis, the visual system, as a function of evolutionary selection, has adapted to the tasks and activities that humans depended upon to survive in our original habitat. The primary objective of the visual system is to provide sharp and single images of objects and landscapes at all distances. Under such conditions, eye movements and fixation changes between far and near

are dynamic and integrated in a systemic interplay with head and body movements. In this context, the tolerance for deviations from optimal conditions in the visual system is relatively high and visual tasks are accomplished without negative costs. However, through our heritage as hunters and gatherers, the EEA has emphasised the importance of distance vision. The visual system is primarily developed for prolonged scanning and fixation operations at longer distances. At close range, most tasks consist of eye-hand coordinated activities that require repeated perception – action couplings. The visual system provides information about details of the object and their affordances, which are subsequently used as basis for manipulatory actions by the hands. Restricted by arm length, the viewing distance in eye-hand coordinated activities varies within a relatively short range. Consequently, the optimum spatial location for hand manipulations seems to be restricted to a rather small envelope located at the body midline in front of the person. In most cases, ecological near-work is carried out in environments that promote alternations of visual focus between the near object and objects or persons at a distance. In order to fixate objects beyond arm’s length it is necessary, in most cases, to decrease the headand/or the gaze angle, yielding higher lines of sight. The perception – action coupling is also affected by this change of visual attention. Higher lines of sight suspend the direct eye-hand coordination. The manipulation of near objects becomes indirect and actions involving some form of distant object manipulation, e.g. pointing or throwing are being potentially initiated. Thus, from an evolutionary perspective it seems reasonable to assume that the oculomotor- and the musculoskeletal system are adapted to near-work situations where visual focus alternates between near and far. In addition, it is reasonable to assume that the ecological near-work posture includes lines of sight inclined downwards, while higher lines of sight are required for more distant objects. It is also plausible to assume that movements implying arm adduction and perhaps also medial rotation of the forehand are closer connected to eye-hand coordination programmes than movements entailing arm abduction and lateral rotation. Regarding VDU work, it is evident that most work tasks are carried out within a small portion of the visual field with limited opportunities to alternate between the near-work task and objects or tasks at longer distances. The lack of dynamic change constitutes a visual condition where natural dynamic vergence and accommodation performance is changed into static muscle

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activity. To maintain its function, muscles in the head, neck, shoulder and upper back are activated [61–63]. Thus, the dispersal of near-work related visual stress not only negatively influences the oculomotor system, but also other muscle systems in the body. This implies that VDU work entails not only visually related stress, but also musculoskeletal stress, both through sustained static and/or repetitive work at low amplitude and indirectly through transmission from the oculomotor system. The joint influence of the different stresses present in a specific work situation may thus have a detrimental effect that is potentially greater than just an additive effect. Taking the ecological and evolutionary analysis of near-work into consideration, it seems evident that several aspects of modern near-work entail behavioural patterns that represent a departure from the motor programmes that have evolved in connection to ecological near-work. In this regard, several aspects of the modern near-work situation act as EN environments, even if the concept of near-work is not. According to the evolutionary stress model, prolonged exposure to these aspects may engender negative health effects. In addition, the dispersal of near-work induced stress not only influences the body directly. It also entails reduced tolerance for deviations from optimal conditions in other respects. If we combine, as we often do, intensive VDU work with other non-optimal conditions we have a situation which we are not evolved to handle. The results are reduced activity, productivity, and quality of life. Thus, from a visual-ecological point of view this implies that VDU work is taxing the visual and oculomotor system on components which are weak and have low resistance for continuous work, since they are “designed” for this type of work only for short and limited periods of time. VDU work is, therefore, a classical example where Nature is lagging behind current adaptational challenges. Our visual system is only partially adapted to the modern computer world and our visuo-motor coping adaptabilities will, therefore, be in a state of chronic stress with a number of stress-related negative consequences. In order to prevent such negative health development one should aim at introducing work postures, workstations, and a work organisation that approximates the conditions found in the environment were evolutionary adaptations to near-work found its current form. The suitability of this approach is demonstrated in a field study conducted by Fostervold et al. [6]. The study compared employees engaged in VDU work with either downward line-of-sight or high line-of-sight. The

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results showed that downward line-of-sight reduced the severity of somatic complaints, lead to fewer days absent, and either had no- or positive effect on oculomotor capacity.

5. Concluding remarks The aim of visual ergonomics and ergonomics in general is to establish and to maintain healthy work environments that people experience as safe and stimulating. The notion is that a good working environment, that emphasise physical conditions and which is perceived as a safe place to be by the employee, will contribute to the development of stress reduction, improved health, and a social climate that stimulates mental growth and productivity. Stress in this context is seen as the result of incongruity between personal characteristics and conditions encountered in the environment, often termed as lacking person – environment fit. To achieve this goal it is necessary not only to understand the impact of health hazards originating from specific technological and environmental sources, but also the interrelationship between those sources and the physiological and psychological adaptations to the environment they inhabit. The present paper calls attention to the need for a theoretical reorientation of ergonomics and human factors. As a vehicle to accomplish this task, this paper points to the development of an evolutionary stress model. Related to VDU work, this model raises some basic questions; what constitutes the environment of evolutionary adaptedness (EEA), what are the subsequent phenotypic adaptations, and to what degree does these adaptations fit the challenges of modern VDU work? As has become evident, providing a work environment that runs counter to our evolutionary adaptations may lead to negative health development and increased risk of human error. Consequently, the principal task of ergonomics and human factors should be to encourage and contribute scientifically to the development of tools, work tasks, and environments that approximate the conditions for which humans are adapted. By doing this, ergonomics would not only succeed in its effort to understand the negative consequences of VDU work; it would also represent a substantial contribution to the general body of knowledge about humans and their relationship to the environment. Scientists and practitioners within the field of ergonomics and human factors should strive for no less.

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