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Abstract. In our living, we often have a sense of being tired due to a mental or physical work, plus a feeling of performance degradation even in the accomplishment of simple tasks. However, these mental states are often not consciously felt or are ignored, an attitude that may result in human failures, errors and even in the occurrence of health problems or on a decrease in the quality of life. States of fatigue may be detected with a close monitoring of some indicators, such as productivity, performance or even the health states. In this work it is proposed a model and a prototype to detect and monitor fatigue based on some of these items. We focus specifically on mental fatigue, a key factor in an individual's performance. With this approach we aim to develop leisure and work context-aware environments that may improve the quality of life and the individual performance of any human being.

a b s t r a c tFatigue, especially in its mental form, is one of the most worrying health problems nowadays. It affects not only health but also motivation, emotions and feelings and has an impact both at the individual and organizational level. Fatigue monitoring and management assumes thus, in this century, an increased importance, that should be promoted by private organizations and governments alike. While traditional approaches are mostly based on questionnaires, in this paper we present an alternative one that relies on the observation of the individual's interaction with the computer. We show that this interaction changes with the onset of fatigue and that these changes are significant enough to support the training of a neural network that can classify mental fatigue in real time. The main outcome of this work is the development of non-invasive systems for the continuous classification of mental fatigue that can support effective and efficient fatigue management initiatives, especially in the context of desk jobs.

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In the present study, we examined whether age influences the effects of mental fatigue on task performance, and if we could validate the use of measures based on typing behavior as an index of the effects of mental fatigue on different aspects of cognition. Young (N = 24, 18–30 years) and middle-aged (N = 24, 50–67 years) participants performed a typewriting task and a mouse targeting task for 120 min. At the beginning and at the end of the experiment the level of subjective fatigue was assessed. During task performance measures based on typing behavior and EEG were recorded. Results showed that subjective fatigue increased over the experiment in both the young and the middle-aged group. Typing speed decreased with time-on-task (ToT) in both age groups, reflected in larger general interkey intervals and in an increase in typing time. In addition, typing accuracy decreased with ToT in the young group, however, not in the middle-aged group, reflected by an increase in typing errors. Moreover, the young group used the backspace key more often with ToT due to delayed error-correction, reflected in larger backspace sequences, resulting in larger interkey intervals and increased typing time. This effect was absent in the middle-aged group. In the young group, the P3 brain potential amplitude decreased over the experiment, which was related to an increase in typing time, longer general interkey intervals, and an increase in typing errors, suggesting that decreased task engagement was related to less efficient typewriting, at least in the young group. These results indicate that measures based on typing behavior could give information about the process of mental fatigue, and in addition suggest that age influences the effect of mental fatigue on typewriting. More specifically, younger adults more often adopt a strategy that emphasizes speed, while middle-aged adults act more error-aversive than younger adults.

The family Discodorididae was previously represented by 11 species in Brazil; however, recently collected specimens from several localities in Rio de Janeiro, in addition to the study of material previously deposited in scientific collections, revealed the existence of 13 taxa: Diaulula greeleyi (MacFarland, 1909), Discodoris hummelincki (Ev. Marcus & Er. Marcus, 1963) comb. nov., Discodoris branneri MacFarland, 1909, Geitodoris pusae (Er. Marcus, 1955), Hoplodoris hansrosaorum Domínguez, García & Troncoso, 2006, Jorunna spazzola Er. Marcus, 1955, Jorunna spongiosa sp. nov., Paradoris mulciber (Ev. Marcus, 1971), Platydoris angustipes (Mörch, 1863), Rostanga byga Er. Marcus, 1958a, Taringa telopia Er. Marcus, 1955, Taringa iemanja sp. nov., and Thordisa diuda Er. Marcus, 1955. Discodoris voniheringi MacFarland, 1909 was previously regarded as nomen dubium, and this view is maintained in the present study. Three new records for the Brazilian coast are recognized among these 13 taxa; the previous record of Diaulula phoca (Ev. Marcus & Er. Marcus, 1967a) is rectified as Discodoris hummelincki comb. nov., constituting the first record of this species from Brazil; two new species, Taringa iemanja sp. nov. and Jorunna spongiosa sp. nov., are described in anatomical detail. The following taxa, which were formerly considered junior synonyms of species studied in this work, have been revalidated: Diaulula nayarita (Ortea & Llera, 1981), from the Pacific coast of Costa Rica, which differs from Diaulula greeleyi in the length and width of caryophyllidia; Discodoris mortenseni Ev. Marcus & Er. Marcus, 1963, from the Caribbean, which is likely to belong to Jorunna, yet differs from Jorunna spazzola in body size and coloration, radula appearance, and number of lamellae in the rhinophores; Jorunna luisae Ev. Marcus, 1976, which differs from Jorunna spazzola in the reproductive system, mainly in the size and shape of the accessory gland; and Thordisa azmani Cervera & García-Gómez, 1989, which differs from Thordisa diuda in the presence of two accessory glands in the genital atrium and the absence of one denticle in the external surface of the inner lateral teeth. Finally, the specimens of Geitodoris pusae reported from the European coast and Mediterranean Sea show differences in general coloration and in the radula, gill, and reproductive system, thereby these specimens likely refer to different taxa.

Nowadays, our lifestyle can lead to a scatter of focus, especially when we attend to several tasks in parallel or have to filter the important information from all the remaining one. In the context of a computer this usually means interacting with several applications simultaneously. Over the day, this significant demand on our brain results in the emergence of fatigue, making an individual more prone to distractions. Good management of the working time and effort invested in each task, as well as the effect of breaks at work, can result in better performance and better mental health, delaying the effects of fatigue. This paper presents a non-intrusive and non-invasive method for measuring distraction and fatigue in an individual and in a group of people. The main aim is to allow team managers to better understand the state of their collaborators, thus preparing them to take better decisions concerning their management.

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