Mental Load Research Articles

Estimation of Distances within Real and Virtual Dental Models as a Function of Task Complexity.

Orthodontists have seen their practices evolve from estimating distances on plaster models to estimating distances on non-immersive virtual models. However, if the estimation of distance using real models can generate errors (compared to the real distance measured using tools), which remains acceptable from a clinical point of view, is this also the case for distance estimation performed on digital models? To answer this question, 50 orthodontists (31 women and 19 men) with an average age of 36 years (σ = 12.84; min = 23; max = 63) participated in an experiment consisting of estimating 3 types of distances (mandibular crowding, inter-canine distance, and inter-molar distance) on 6 dental models, including 3 real and 3 virtual models. Moreover, these models were of three different levels of complexity (easy, medium, and difficult). The results showed that, overall, the distances were overestimated (compared to the distance measured using an instrument) regardless of the situation (estimates on real or virtual models), but this overestimation was greater for the virtual models than for the real models. In addition, the mental load associated with the estimation tasks was considered by practitioners to be greater for the estimation tasks performed virtually compared to the same tasks performed on plaster models. Finally, when the estimation task was more complex, the number of estimation errors decreased in both the real and virtual situations, which could be related to the greater number of therapeutic issues associated with more complex models.

Comparison of 2D and autostereoscopic 3D visualization during mixed reality simulation.

In general minimally invasive surgical procedures, surgeons are tied to 2D visualization, leading to the loss of depth perception. This can lead to large mental load for the surgeons and may be responsible for the long learning curve. To restore the sense of depth, this study investigated the use and benefits of an autostereoscopic (3D) display during a simulated laparoscopic task. A mixed reality simulator was developed for comparing the performance of participants while using 2D and autostereoscopic 3D visualization. An electromagnetic sensor was mounted on a physical instrument, and its pose was mapped to the virtual instrument. The virtual scene was developed using Simulation Open Framework Architecture (SOFA). Finite element modeling was used to calculate interaction forces, which were then mapped to visual soft tissue deformation. Ten non-expert participants completed a virtual laparoscopic task, where the subjects were asked to contact eighteen target areas distributed on the surface of the vagina, both in 2D and 3D. Results showed an improvement with 3D vision in task completion time (-16%), total traveled distance (-25%) and errors made (-14%). There was no difference in the average contact forces between the vagina and the instrument. Only the difference in time and forces were shown to be statistically significant. Overall, autostereoscopic 3D showed superiority over conventional 2D visualization. The traveled trajectory increased in 2D as the instrument was retracted more between the targets to avoid contact. The 2D and 3D deformation upon contact seems not to contribute differently to force perception. However, the participants only had visual feedback, but no haptic feedback. Therefore, it could be interesting to include haptic feedback in a future study.

Quantification study of mental load state based on AHP–TOPSIS integration extended with cloud model: methodological and experimental research

AbstractMental load affects the work efficiency and mental health of operators, and it has a vital effect on the efficiency and reliability of human–machine systems. In this study, the evaluation index system of operators’ mental load was used to quantitatively evaluate the mental load state of workers. The system was established by selecting indices from the operators’ physiological parameters, subjective feelings, and time perception. We propose an extended cloud evaluation model of mental load states that combines cloud model (CM) theory with analytic hierarchy process (AHP) and technique for order preference by similarity to ideal solution (TOPSIS) and provides mental load levels. An energetic material initiation experiment was conducted to evaluate the mental load state of the operators using the proposed method, and the results of a fuzzy comprehensive evaluation and subjective questionnaire were used to verify the performance of the method. The results show that the extended CM evaluation method scientifically and reliably quantified the mental load state. Applying the AHP-TOPSIS integration extended with the CM theory evaluation method in mental load state evaluation provides a new scientific method for studying the quantification of the mental load state and occupational health of workers in hazardous environments. The results of this study are a reference for assessing the mental state of personnel and analyzing occupational suitability for dangerous posts.

Caregivers' experiences of end-of-life caregiving to severely ill relatives with cancer dying at home: A qualitative study in the Faroe Islands.

It is common among people with advanced cancer to wish to die at home, but only a few succeed in doing so. The willingness of family members to care for a person, who wants to die at home, is crucial This qualitative study aimed to provide insight into conditions that make dying at home possible in a small-scale society and to describe family caregivers' experiences of providing end-of-life care in a private home setting. Thirteen caregivers were interviewed, their ages varying from 39 to 84 years. A phenomenological approach, inspired by Giorgi, was applied. Two essential structures captured the experience of caring at home until death: 'Managing end-of-life care' and 'meaningfulness in a time of impending death'. It was mainly the family, and especially family members with a healthcare background, together with the district nurses, who supported the caregivers in managing the care of a dying relative at home. Being able to fulfil their relative's wish to die at home and to come closer together as a family made the caregivers feel their efforts meaningful. Our findings point to the importance of having access to home care day and night for the caregivers to feel secure during the night-time. As of now, this is only an option in larger towns in the Faroe Islands, which might also be the case in outskirts areas in other countries. Our findings also showed an unmet need for support to ease the mental load on caregivers. Establishing an outgoing interdisciplinary palliative team would help to increase the number of people who want to die at home and succeed in doing so by giving the caregivers emotional and advisory support.

Prediction of Cognitive Load from Electroencephalography Signals Using Long Short-Term Memory Network

In recent years, the development of adaptive models to tailor instructional content to learners by measuring their cognitive load has become a topic of active research. Brain fog, also known as confusion, is a common cause of poor performance, and real-time detection of confusion is a challenging and important task for applications in online education and driver fatigue detection. In this study, we propose a deep learning method for cognitive load recognition based on electroencephalography (EEG) signals using a long short-term memory network (LSTM) with an attention mechanism. We obtained EEG signal data from a database of brainwave information and associated data on mental load. We evaluated the performance of the proposed LSTM technique in comparison with random forest, Adaptive Boosting (AdaBoost), support vector machine, eXtreme Gradient Boosting (XGBoost), and artificial neural network models. The experimental results demonstrated that the proposed approach had the highest accuracy of 87.1% compared to those of other algorithms, including random forest (64%), AdaBoost (64.31%), support vector machine (60.9%), XGBoost (67.3%), and artificial neural network models (71.4%). The results of this study support the development of a personalized adaptive learning system designed to measure and actively respond to learners' cognitive load in real time using wireless portable EEG systems.

Changes in Perceived Mental Load and Motor Performance during Practice-to-Learn and Practice-to-Maintain in Basketball

Attentional resource allocation during sports practice is associated with the players' perceived mental load. However, few ecological studies address this problem by considering the players' characteristics (e.g., practice experience, skill and cognition). Therefore, this study aimed to analyse the dose-response effect of two different types of practice, each with different learning objectives, on mental load and motor performance by using a linear mixed model analysis. Forty-four university students (age 20.36 ± 3.13 years) participated in this study. Two sessions were conducted, one based on a standard rules 1 × 1 basketball situation ("practice to maintain") and one with motor, temporal and spatial restrictions in 1 × 1 tasks ("practice to learn"). "Practice to learn" produced a higher perceived mental load (NASA-TLX scale) and a worse performance than "practice to maintain", but was moderated by experience and inhibition (p = 0.001). The same happens in the most demanding restriction (i.e., temporal, p < 0.0001). The results showed that increasing the difficulty of 1 × 1 situations through restrictions harmed the player's performance and increased their perceived mental load. These effects were moderated by previous basketball experience and the player's inhibition capacity, so the difficulty adjustment should be based on the athletes themselves.

A virtual reality simulation of a novel way to illuminate the surgical field - A feasibility study on the use of automated lighting systems in the operating theatre.

Surgical lighting systems have to be re-adjusted manually during surgery by the medical personnel. While some authors suggest that interaction with a surgical lighting system in the operating room might be a distractor, others support the idea that manual interaction with the surgical lighting system is a hygiene problem as pathogens might be present on the handle. In any case, it seems desirable to develop a novel approach to surgical lighting that minimizes the need for manual interaction during a surgical procedure. We investigated the effect of manual interaction with a classical surgical lighting system and simulated a proposed novel design of a surgical lighting system in a virtual reality environment with respect to performance accuracy as well as cognitive load (measured by electroencephalographical recordings). We found that manual interaction with the surgical lights has no effect on the quality of performance, yet for the price of a higher mental effort, possibly leading to faster fatigue of the medical personnel in the long run. Our proposed novel surgical lighting system negates the need for manual interaction and leads to a performance quality comparable to the classical lighting system, yet with less mental load for the surgical personnel.

“Don’t Put Color in Your Hair, Don’t Do This, Don’t Do That”: Canadian Mayors’ Mixed Gender Performance on Social Media

AbstractAlthough mayors can have important impacts on citizens’ daily lives, local politics remains understudied, especially compared with national and regional politics. This study focuses on Canadian mayors’ digital political gender performance—or self-presentation—on Facebook, Twitter, and Instagram and the context in which this gendered performance arises. Overall, results confirm that mayors’ gendered performances are on a continuum rather than binary. Results from a visual content analysis of nine Canadian mayors’ social media accounts show that, broadly speaking, women mayors gravitate toward congruent, mixed gendered performances and avoidance strategies, whereas men mayors also display mixed performance of their gender, while more freely exploring congruent and incongruent approaches to gendered stereotypes. Additionally, semistructured interviews with these mayors show that women mayors still work under added constraints because of their gender, which translates into comments on their appearance, attitude, and lifestyle choices; increased aggression and lack of respect; and a generally greater mental load.

Changes in smoking behaviour among healthcare workers with COVID-19

IntroductionThe COVID-19 pandemic had a considerable psychosocial impact on healthcare workers (HCWs) who were constantly requested during this era with an increased risk of infection. This implies behavioural changes, especially in smoking behaviour.ObjectivesTo study smoking behaviour in HCWs with COVID-19.MethodsA cross-sectional descriptive study conducted in the department of occupational pathology of Charles Nicolle Hospital in Tunis involving the smoking HCWs affected by COVID-19 during the period from September 1, 2020, to February 28, 2021. The data collection was carried out by a telephone call using a standardized questionnaire.ResultsDuring the study period, 61 smoking HCWs were identified. Thirty-two patients agreed to answer the questionnaire, with a response rate of 52%. The mean age was 41±10 years. The sex ratio (M/F) was 1.46. Half of the participants had comorbidities. The most represented occupational categories were blue-collar workers (n=11) followed by nurses (n=10) and physicians (n=7). The median professional seniority was 13 [3.5; 20] years. The mean age of smoking initiation was 20±5 years. The most common mode of smoking was cigarettes (93%) with an average consumption of 19 cigarettes per day. Water pipe smoking was noted in 3 patients. All patients started smoking before the COVID-19 infection. Strong tobacco dependence was noted in 25% of patients. Twenty-one per cent of the population had moderate dependence. Half of the participants maintained the same level of smoking as before the COVID-19 infection. An increase in smoking was noted in 34% of patients. A decrease in the level of smoking was reported by 15% of respondents. Four participants stopped smoking after COVID-19 infection. The reasons for smoking cessation were COVID-19 damage (n=3) and confinement with family (n=1).ConclusionsThe change in smoking behaviour during the COVID-19 pandemic is notable, particularly in HCWs who are exposed to a high physical and mental load. The presumed association of smoking with severe forms of COVID-19 infection makes tobacco control in HCWs an obligation in order to preserve the continuity of care.Disclosure of InterestNone Declared

Chronic diseases among paramedics and their impact on mental health

IntroductionWorking in a care setting is characterised by an increased mental and physical load. During their professional life, personnel in this sector can develop essentially degenerative pathologies, which could influence their professional career as well as their psychological balance.ObjectivesWe aimed to evaluate the impact of chronic pathologies on the prevalence of anxiety and depression among this group.MethodsWe conducted a cross-sectional study in hospitals in Sfax using a self-administered questionnaire. This questionnaire evaluated socio-demographic, professional, and clinical characteristics as well as an evaluation of the degree of anxiety and depression by the HAD questionnaire.ResultsOur population consisted of 120 participants. The average age was 37 years, with a female predominance (a sex ratio of 0.69). The chronic pathologies found in the participants were mainly diabetes (18%), high blood pressure (4%), and rheumatic disease (6.7%). The average anxiety score was 8.18± 3.5 and that of depression was 9.02± 3.5. Certain depressive and anxious signs were found in 28.4% and 23.6% of participants, respectively. Although the average scores for anxiety and depression were higher in the subgroup of personnel with chronic pathologies (respectively, 9.8 versus 9.04 and 9.3 versus 8.46), these differences were not statistically significant (p &gt; 0.05).ConclusionsPhysical and mental health are both important to ensure a balanced life. Having good control of somatic illness can improve mental health.Disclosure of InterestNone Declared

MEDICAL FITNESS IN WORKERS WITH PSYCHIATRIC DISORDERS

IntroductionMental health disorders are among the most burdensome health concerns in the world; it affects more than 970 million people in 2019. These disorders deteriorate all aspects of life, especially the professional field, impacting mainly physical capability, daily functioning, and productivity among the working-age population.ObjectivesTo study the socio-professional and medical characteristics of workers with psychiatric disorders and to assess the repercussions of these pathologies on work ability.MethodsA descriptive and retrospective study included all the medical files of workers with psychiatric disorders who were referred to the occupational medicine department at Charles Nicolle Hospital for a medical opinion of fitness for work during the period from January 1, 2014, to December 31, 2020.ResultsThe average age of the 224 cases collected was 41.74± [25-60 years] with a sex ratio of 0.67. The average professional seniority was 13.4 years±8.27 years. The most common occupational sectors were health (38.1%) and communication (20.2%). The patients were mainly suffering from either an anxiety-depressive disorder (36.6%) or psychosis (11.6%). These included 21 cases of bipolar disorder, 21 cases of schizophrenia, two cases of chronic hallucinatory psychosis and 3 cases of delusional psychosis. Forty-three patients were fit to continue working, 133 patients were fit with restrictions and twenty-six were unfitted to work.A professional reclassification was recommended for 37 patients in positions with a lower mental load. One employee suffering from advanced schizophrenia was offered early retirement on grounds of disability. Permanent unfitness was pronounced in 11.6% of cases.ConclusionsThe impact of mental disorders on cognitive abilities can be so significant as to result in temporary or permanent unfitness for work. However, the decision of medical fitness for work for the same psychiatric pathology may vary from one individual to another and from one workstation to another.Disclosure of InterestNone Declared

Quality of sleep among trainee doctors at the Charles Nicolle Hospital during the 2nd wave of COVID19

IntroductionSleep quality depends on several factors such as smoking, physical activity, diet, and certain pathologies such as obstructive sleep apnoea syndrome. Indeed, following a COVID-19 infection, several trainee doctors complained about a deterioration of their sleep quality.ObjectivesTo evaluate the quality of sleep of medical trainees working at Charles Nicolle Hospital who were infected by SARS-COV2.MethodsWe conducted a descriptive cross-sectional study, among medical trainees at Charles Nicolle Hospital, infected by COVID-19 during the period from July 2020 to November 2020. Sleep quality was evaluated by the Pittsburgh Sleep Quality Index (PSQI) questionnaire. Trainees were contacted during the period August 2022 to September 2022.ResultsFifty-three trainee doctors have joined our study. Forty-five of them had a significant sleep disturbance with a Pittsburgh Sleep Quality Index (PSQI) greater than five. The average age was 29.4±3.07 years old with a female majority (75%). No psychiatric history was found. The most affected category of trainees were residents (74%), particularly those working in the general surgery department (18%) and the anaesthesia and intensive care department (9%). Among those trainees, 80% had night shifts with an average of six shifts per month. Sleep latency was high in 20% of cases. A sleep duration of less than five hours per night was found in 18% of the cases. Six participants reported using sleeping pill three to four times a week.ConclusionsOur study revealed a significant sleep disturbance among trainee doctors. This could be due to the SARS-COV2 infection but can also be explained by the night shifts burden and the great mental load at work during this pandemic period.Disclosure of InterestNone Declared

The influence of sports orientation means on the development and increase of the speed of military officers-artillery

Scientific and technical progress in the military sphere requires the Armed Forces to constantly improve weapons and combat equipment, increases the requirements for combat skills, physical and mental preparedness of servicemen, and the training of highly qualified officers.&#x0D; The use of means of sports orientation can become an additional component in the formation of qualities necessary for the better formation of skills from exercises of a military nature, especially with regard to the development of willpower, improvement of physical and psychological readiness of military personnel.&#x0D; Sports orientation belongs to the types of sports that combine both long and intense physical and mental loads. It sets in motion not only the musculoskeletal system, but also activates the activity of the Central Nervous System. Therefore, the special qualities of an orienteer are endurance, dexterity, coordination and reaction speed, concentration of attention, creative thinking, strong-willed qualities such as determination, emotional stability, which is important for military personnel who perform combat tasks in the conditions of modern warfare.&#x0D; Thus, in order to increase the effectiveness of the tasks of military professional activity, the efficiency of the execution of operational tasks by military personnel requires high speed and coordination. The article considers a method of increasing the speed characteristics of artillery reconnaissance specialists by using elements of training of orienteers.

Effects of manipulator operation task and troubleshooting task on blood pressure indexes of oceanauts

Objective: To explore the characteristics and rules of blood pressure changes in oceanauts during simulated operation of manipulator and troubleshooting tasks with different difficulty. Methods: In July 2020, 8 deep-sea manned submersible oceanauts, 6 males and 2 females, were selected as objects. In the 1∶1 model of Jiaolong deep-sea manned submersible, the oceanauts performed manipulator operation tasks and troubleshooting tasks with different difficulties, measured the continuous blood pressure of the oceanauts, filled in the NASA Task Load Index (NASA-TLX scale) after the completion of a single mission, and the changes of systolic pressure (SBP), diastolic pressure (DBP), mean arterial pressure (MAP) and mental workload were analyzed. Results: In a single task, the SBP, DBP and MAP of the oceanauts increased first and then decreased. The blood pressure values at the third minute were significantly lower than those at the first minute (P<0.01), and those at the fifth minute were significantly higher than those at the third minute (P<0.01). When performing the same task, compared with the quiet state, SBP, DBP and MAP increased when the oceanauts performed low difficulty, high difficulty, high difficulty+2-back manipulator operation task and troubleshooting task (P<0.05). When the task difficulty was the same, the SBP and MAP of oceanauts performing manipulator operation tasks were higher than those of oceanauts performing troubleshooting tasks (P<0.05). Compared with low difficulty tasks, the scores of NASA-TLX scale for oceanauts performing high difficulty manipulator operationtasks were significantly higher (P<0.05). Compared with the low difficulty task and high difficulty task, the scale score of the high difficulty+2-back troubleshooting task was significantly higher (P<0.05). When the task difficulty was the same, the scale scores of low difficulty and high difficulty manipulator operation tasks were significantly higher than those of troubleshooting tasks (P<0.05). SBP, DBP, MAP of No. 1, No. 3, No. 4, No. 5, and No. 7 oceanauts (all of whom had 6 years of diving) were positively correlated with NASA-TLX scale scores (r>0.8, P<0.05) . Conclusion: In the process of manned deep-sea diving, when the oceanauts perform manipulator operation tasks and troubleshooting tasks, with the increase of task difficulty, the mental load of oceanauts increases, and the blood pressure index increases significantly in a short time. At the same time, improving the proficiency of operation can reduce the variation range of blood pressure indexes. Blood pressure can be used as an effective reference to evaluate the difficulty of operation and guide scientific training.

The pre-ejection period is a highly stress dependent parameter of paramount importance for pulse-wave-velocity based applications.

The pulse-wave-velocity, is used for indirect, cuff-less, continuous blood pressure estimation. It is commonly detected by measuring the time delay between a defined point in an ECG and the arrival of the peripheral pulse wave (e.g., oxygen saturation sensor). The period between electrical stimulation of the heart (ECG) and actual blood ejection from the heart is called the pre-ejection period (PEP). This study aims at characterizing the PEP under mental and physical stress with focus on its relations to other cardiovascular parameters such as heart rate and importance for blood pressure (BP) estimation. We measured the PEP in 71 young adults at rest, under mental (TSST) and physical stress (ergometer) via impedance-cardiography. The PEP is highly dependent on mental and physical load. It is strongly correlated with indicators of sympathetic strain (p < 0.001). At rest (mean 104.5 ms), the PEP shows a high interindividual variability but small intraindividual variability. Mental stress decreases the PEP by 16% (mean 90.0 ms) while physical stress halves PEP (mean 53.9 ms). The PEP does correlate differently with heart rate under differing circumstances (rest: R 2 0.06, mental stress: R 2 0.29, physical stress: R 2 0.65). Subsequently, using PEP and heart rate enables the discrimination of rest, mental and physical strain with a positive predictive value of 93%. The PEP is a cardiovascular parameter with large interindividual variability at rest and subject-depended dynamic under load which is of great importance for ECG-based pulse-wave-velocity (PWV) determination. Considering its variability and large impact on the pulse arrival time, PEP is a crucial factor in PWV based BP estimation.

The Effects of Routinization on Radical and Incremental Creativity: The Mediating Role of Mental Workloads.

An important question within the creativity literature is whether routinization inhibits individuals' creative performance. Scholars have concentrated on complex and demanding jobs that promote creativity while ignoring the potential effects of routinized activities on creativity. Moreover, little is known about the impact of routinization on creativity, and the few studies investigating this matter have reported inconclusive and inconsistent results. This study investigates the mixed impacts of routinization on creativity by examining whether routinization has a direct impact on two dimensions of creativity or an indirect impact through the mediating role of mental workloads, such as mental effort load, time load, and psychological stress load. Based on multisource and time-lagged data from 213 employee-supervisor dyads, we found a positive direct effect of routinization on incremental creativity. In addition, routinization had both an indirect effect on radical creativity via time load and on incremental creativity via mental effort load. Implications for theory and practice are discussed.

Failed Attempt to Recommend Noise Cancelling Headphones for Knee Arthroplasty Surgeons-Results of a Pilot Study.

Background and Objectives: Noise exposure during total knee arthroplasty (TKA) has been demonstrated to exceed thresholds that are deemed as over-exposure by industry noise level standards. With orthopedic surgeons being at risk of suffering from Noise Induced Hearing Loss, the purpose of this pilot study was to evaluate the viability of the use of industry grade active noise cancelling headphones (ANCH) during TKA. Material and Methods: In this prospective pilot study, 10 TKA were performed. In five of these cases, surgeon, assistant, scrub nurse and anesthetist wore ANCH with automatic noise level dependent noise attenuation above 82 dB. A validated 14-item questionnaire was used after each case to evaluate the quality of communication, performance, teamwork and mental load. In seven cases a calibrated sound level meter was used to measure the operating theatre noise. Peak sound level (LApeak), A-weighted continuous sound level (LAeq) and A-weighted noise exposure averaged for an 8-h time-period (LEPd) were calculated. Results: There was no perceived benefit of ANCH for the surgeons (p = 0.648), assistants (p = 0.908) and scrub nurses (p = 0.251). There was an overall improvement observed by anesthetists (p = 0.001). A worse communication while wearing ANCH was reported by surgeons but not by the rest of the team. Average LApeak was 90.6 ± 3.2 dB(C), LAeq was 61.9 ± 1.0 dB(A) and LEPd was 53.2 ± 1.2 dB(A). Conclusions: Industry grade ANCH seem to provide no benefit for surgeons, assistants and scrub nurses during TKA, while anesthesiologists seem to benefit from the use of ANCH during TKA. Due to the limitations of this pilot study, further studies with larger study populations are necessary to adequately investigate the use of ANCH during TKA.

Cognitive Reorganization Due to Mental Workload: A Functional Connectivity Analysis Based on Working Memory Paradigms

Mental workload has a major effect on the individual’s performance in most real-world tasks, which can lead to significant errors in critical operations. On this premise, the analysis and assessment of mental workload attain high research interest in both the fields of Neuroergonomics and Neuroscience. In this work, we implemented an EEG experimental design consisting of two distinct mental tasks (mental arithmetic task, n-back task), each with two conditions of complexity (low and high) to investigate the task-related and task-unrelated workload effects. Since mental workload is an intricate phenomenon involving multiple brain areas, we performed a graph theoretical analysis estimating the Phase Locking Index (PLI) in four frequency bands (delta, theta, alpha, beta). The brainwave-dependent network results show statistically significant reductions in clustering coefficient, characteristic path length, and small-worldness metrics with higher workload in both tasks across several bands. Moreover, functional connectivity analysis indicates a task-independent fashion of the brain topological re-organization with increasing mental load. These results revealed how the brain network is re-organized with increasing mental workload in a task-independent way. Finally, the network metrics were used as classification features, leading to high performance in workload level discrimination.

Study on Personal Identification Which is Stable Against the Change of Room Temperature Using Thermal Image

Since the temperature distribution of the face varies among individuals, there is a possibility that it can be used for personal authentication. This paper proposes a method of using the high temperature region of the face, which is stable during personal authentication and resistant to changes in room temperature. The method obtained a 87% recognition rate in individual identification experiments under a variety of room temperature. In addition, this paper experimentally explains the method is stability against internal and external factors such as mental stress load and direct wind. Furthermore, combining this method with conventional face recognition methods using visible images, it will be possible to improve the authentication rate and avoid various risks.

Variation and Use of Relativizers in the Spanish of Medellín, Colombia: A Corpus-Based Study

The study of relativizers in the Spanish language has not been quite explored from a sociolinguistic point of view. A few research papers have analyzed varieties found in Santiago de Chile, Mexico City, Sevilla, and Madrid. Nevertheless, none of them has addressed a Colombian variety in depth. This variationist study aims to fill the gap by reporting the results of a correlational study focused on the use and variation of relativizers in the preseea-Medellín corpus. An anova test, a Games-Howell test, multiple Tukey’s tests, and pairwise comparisons t-tests with Bonferroni correction were run to identify the variables with significant effects (e.g., geographical position, gender, level of education, and social class). Results suggest that, while there is significant diatopic variation in the selection of relativizers, diastratic variables have a minor role in their frequency of use. It was also noted that while the use of the pronoun que tends to spread in all varieties of Spanish, the relative adjectives cuyo and cuanto continue their trend towards disuse. Further studies are necessary to determine if this tendency to simplification is related to psycholinguistic constraints (i.e. mental load) or functional aspects of Spanish. Finally, this study opens the doors to the analysis of relativizers in other varieties of Colombian Spanish from a sociolinguistic perspective.