Using mobile eye tracking to measure cognitive load through gaze behavior during walking in lower limb prosthesis users: A preliminary assessment.

BACKGROUND: Lower limb amputation does not affect only physical and psychological functioning but the use of a prosthetic device can also lead to increased cognitive demands. Measuring cognitive load objectively is challenging, and therefore, most studies use questionnaires that are easy to apply but can suffer from subjective bias. Motivated by this, the present study investigated whether a mobile eye tracker can be used to objectively measure cognitive load by monitoring gaze behavior during a set of motor tasks. METHODS: Five prosthetic users and eight able-bodied controls participated in this study. Eye tracking data and kinematics were recorded during a set of motor tasks (level ground walking, walking on uneven terrain, obstacle avoidance, stairs up and ramp down, as well as ramp up and stairs down) while the participants were asked to focus their gaze on a visual target for as long as possible. Target fixation times and increase in pupil diameters were determined and correlated to subjective ratings of cognitive load. FINDINGS: Overall, target fixation time and pupil diameter showed strong negative and positive correlations, respectively, to the subjective rating of cognitive load in the able-bodied controls (-0.75 and 0.80, respectively). However, the individual correlation strength, and in some cases, even the sign, was different across participants. A similar trend could be observed in prosthetic users. INTERPRETATION: The results of this study showed that a mobile eye tracker may be used to estimate cognitive load in prosthesis users during locomotor tasks. This paves the way to establish a new approach to assessing cognitive load, which is objective and yet practical and simple to administer. Nevertheless, future studies should corroborate these results by comparing them to other objective measures as well as focus on translating the proposed approach outside of a laboratory.

Differences in the mutual eye gaze of bonobos (Pan paniscus) and chimpanzees (Pan troglodytes).

Eye gaze is widespread in nonhuman primate taxa and important for social cognition and communicative signaling. Bonobos and chimpanzees, two closely related primate species, differ in social organization, behavior, and cognition. Chimpanzees' eye gaze and gaze following has been studied extensively, whereas less is known about bonobos' eye gaze. To examine species differences using a more ecologically relevant measure than videos or pictures, the current study compared bonobo and chimpanzee mutual eye gaze with a human observer. A multivariate analysis of variance revealed significant species differences in frequency and total duration, but not bout length, of mutual eye gaze (p < .001). Specifically, bonobos engage in mutual eye gaze more frequently and for longer total duration than chimpanzees. These results are likely related to species differences in social behavior and temperament and are consistent with eye-tracking studies in which bonobos looked at the eye region of conspecifics (in pictures and videos) longer than chimpanzees. Future research should examine the relationship between mutual eye gaze and gaze following, as well as examine its genetic and neurological correlates. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Learning Scan Paths of Eye Movement in Autism Spectrum Disorder.

Eye tracking studies have demonstrated deficits in attention in individuals with Autism Spectrum Disorder (ASD) for a range of different social attention-based tasks. Here we examined social attention skills in a large sample of ASD participants (n = 120), using eye tracking data from a social information processing task, and compared them with a typically developing (TD) group (n = 35). Assuming eye movement parameters are random variables generated by an underlying stochastic process, we modeled the fixation sequences of participants in ASD and TD groups with a Hidden Markov Model. The Regions of Interests (ROIs), modeled as hidden states, corresponded to the true ROIs with a prediction accuracy of >90% for each group. The transition between ROIs revealed bias towards a specific area in the scene in ASD group, which deviated from the TD group. Objective time-dynamic measures of gaze patterns can potentially serve as useful endpoints in ASD diagnosis. Clinical Trial Registration: NCT02299700.

Difference in eye movements during gait analysis between professionals and trainees.

INTRODUCTION: Observational gait analysis is a widely used skill in physical therapy. Meanwhile, the skill has not been investigated using objective assessments. The present study investigated the differences in eye movement between professionals and trainees, while observing gait analysis. METHODS: The participants included in this study were 26 professional physical therapists and 26 physical therapist trainees. The participants, wearing eye tracker systems, were asked to describe gait abnormalities of a patient as much as possible. The eye movement parameters of interest were fixation count, average fixation duration, and total fixation duration. RESULTS: The number of gait abnormalities described was significantly higher in professionals than in trainees, overall and in limbs of the patient. The fixation count was significantly higher in professionals when compared to trainees. Additionally, the average fixation duration and total fixation duration were significantly shorter in professionals. Conversely, in trunks, the number of gait abnormalities and eye movements showed no significant differences between groups. CONCLUSIONS: Professionals require shorter fixation durations on areas of interest than trainees, while describing a higher number of gait abnormalities.

Gaze Tracking and Point Estimation Using Low-Cost Head-Mounted Devices.

In this study, a head-mounted device was developed to track the gaze of the eyes and estimate the gaze point on the user's visual plane. To provide a cost-effective vision tracking solution, this head-mounted device is combined with a sized endoscope camera, infrared light, and mobile phone; the devices are also implemented via 3D printing to reduce costs. Based on the proposed image pre-processing techniques, the system can efficiently extract and estimate the pupil ellipse from the camera module. A 3D eye model was also developed to effectively locate eye gaze points from extracted eye images. In the experimental results, average accuracy, precision, and recall rates of the proposed system can achieve an average of over 97%, which can demonstrate the efficiency of the proposed system. This study can be widely used in the Internet of Things, virtual reality, assistive devices, and human-computer interaction applications.

Social modulators of gaze-mediated orienting of attention: A review.

Humans tend to shift attention according to others' eye-gaze direction. This is a core ability as it permits to create pervasive relationships among individuals and with the environment around them. In the beginning, this form of social orienting was considered a reflexive phenomenon, but in recent years evidence has shown that it is also permeable to several social factors related to the observer, the individual depicted in the cueing face, and the relationship between them. The major goal of this work is to provide a comprehensive overview concerning the role that social variables can play in shaping covert gaze cueing in healthy adults, critically examining both the modulatory social factors for which evidence is more robust and those for which evidence is mixed. When available, overt attention studies will also be discussed. Finally, a novel theoretical framework linking these social and attention domains will be also introduced.

Gaze and Movement Assessment (GaMA): Inter-site validation of a visuomotor upper limb functional protocol.

BACKGROUND: Successful hand-object interactions require precise hand-eye coordination with continual movement adjustments. Quantitative measurement of this visuomotor behaviour could provide valuable insight into upper limb impairments. The Gaze and Movement Assessment (GaMA) was developed to provide protocols for simultaneous motion capture and eye tracking during the administration of two functional tasks, along with data analysis methods to generate standard measures of visuomotor behaviour. The objective of this study was to investigate the reproducibility of the GaMA protocol across two independent groups of non-disabled participants, with different raters using different motion capture and eye tracking technology. METHODS: Twenty non-disabled adults performed the Pasta Box Task and the Cup Transfer Task. Upper body and eye movements were recorded using motion capture and eye tracking, respectively. Measures of hand movement, angular joint kinematics, and eye gaze were compared to those from a different sample of twenty non-disabled adults who had previously performed the same protocol with different technology, rater and site. RESULTS: Participants took longer to perform the tasks versus those from the earlier study, although the relative time of each movement phase was similar. Measures that were dissimilar between the groups included hand distances travelled, hand trajectories, number of movement units, eye latencies, and peak angular velocities. Similarities included all hand velocity and grip aperture measures, eye fixations, and most peak joint angle and range of motion measures. DISCUSSION: The reproducibility of GaMA was confirmed by this study, despite a few differences introduced by learning effects, task demonstration variation, and limitations of the kinematic model. GaMA accurately quantifies the typical behaviours of a non-disabled population, producing precise quantitative measures of hand function, trunk and angular joint kinematics, and associated visuomotor behaviour. This work advances the consideration for use of GaMA in populations with upper limb sensorimotor impairment.

The upper disparity limit increases gradually with eccentricity.

Stereopsis is important for tasks of daily living such as eye-hand coordination. It is best in central vision but is also mediated by the periphery. Previously we have shown that individuals with central-field loss who have residual stereopsis in the periphery perform better at an eye-hand-coordination task when they perform the task binocularly rather than monocularly. Here we seek to determine what sets the limit of stereopsis, defined as the largest disparity that supports the sustained appearance of depth, in the near periphery in healthy individuals. While stereoacuity thresholds increase sharply with eccentricity, Panum's area increases much more slowly. We used a rigorous method to determine the uppermost limit of disparity. At long durations, the two half-images that define a large disparity appear as two isolated targets in the same flat plane; small incremental changes in disparity produce changes in the separation between the half-images, and disparity magnitude can be judged on the basis of separation, like a monocular width judgment. The disparity limit is the point at which the threshold for judging dichoptic separation between the half-images is equal to the monocular width-discrimination threshold. The disparity limit at 10° was a factor of 2-4 times larger than the fovea, regardless of the meridian tested. The increase in the disparity limit with eccentricity was shallow, similar to that of Panum's area. Within this disparity limit, disparity increment thresholds were comparable for foveal and peripheral targets, illustrating the significance and utility of peripheral stereopsis, especially in the absence of foveal stereopsis.

The visual cues that drive the self-assessment of body size: Dissociation between fixation patterns and the key areas of the body for accurate judgement.

A modified version of the bubbles masking paradigm was used in three experiments to determine the key areas of the body that are used in self-estimates of body size. In this paradigm, parts of the stimuli are revealed by several randomly allocated Gaussian "windows" forcing judgements to be made based on this partial information. Over multiple trials, all potential cues are sampled, and the effectiveness of each window at predicting the judgement is determined. The modified bubbles strategy emphasises the distinction between central versus edge cues and localises the visual features used in judging one's own body size. In addition, eye-movements were measured in conjunction with the bubbles paradigm and the results mapped onto a common reference space. This shows that although observers fixate centrally on the torso, they are actually directing their visual attention to the edges of the torso to gauge body width as an index of body size. The central fixations are simply the most efficient way of positioning the eye to make this estimation. Inaccurate observers are less precise in their central fixations and do not evenly allocate their attention to both sides of the torso's edge, illustrating the importance of efficiently sampling the key information.

Effect of model race and viewing perspective on body attractiveness and body size assessment in young Caucasian women: an eye-tracking study.

Research has indicated that Caucasian women gaze more often at waist-hip and chest regions than other local body areas when assessing female body attractiveness and body size, and this stereotypical gaze distribution is further modulated by their own body satisfaction and body composition. However, little is known whether the model race and viewing perspective could affect women's body-viewing gaze behaviour and body perception. Here, we presented female body images of Caucasian, Asian and African avatars in a continuum of common dress sizes in full frontal, mid-profile and rear view, and asked young Caucasian women to rate the perceived body attractiveness and body size. Their body-viewing gaze distributions were then correlated with their behavioural responses, their own body composition and body satisfaction. Our analysis revealed a clear in-group favouritism, in which Caucasian women tended to rate Caucasian avatars more attractive and slimmer than Asian and African avatars. Their body-viewing gaze patterns, on the other hand, were not affected by avatar race but were modulated by viewing perspectives. The frontal-view body (especially upper-body and waist-hip regions) attracted the highest proportion of viewing time, followed by the mid-profile view and then the rear-view body. Furthermore, our participants' own body composition and satisfaction level did not affect their judgement of other women's body attractiveness and body size, but could influence their gaze allocation at local body features. It seems that both body perception and body-viewing gaze behaviour are subject to group and individual biases.

Microperimetry and swept-source optical coherence tomography in the assessment of the preferred retinal locus in a child with macular retinoblastoma in the remaining eye.

Assessing the visual capabilities that remain to children affected with bilateral retinoblastoma has relied on psychophysical tests based on recognition visual acuity. We report a case in which fundus-driven perimetry and swept-source optical coherence tomography was performed in a patient with a macular tumor in the remaining eye as a novel way of further assessing fixation after oncological disease and treatment.

The Multisensory Attention Assessment Protocol (MAAP): Characterizing individual differences in multisensory attention skills in infants and children and relations with language and cognition.

Multisensory attention skills provide a crucial foundation for early cognitive, social, and language development, yet there are no fine-grained, individual difference measures of these skills appropriate for preverbal children. The Multisensory Attention Assessment Protocol (MAAP) fills this need. In a single video-based protocol requiring no language skills, the MAAP assesses individual differences in three fundamental building blocks of attention to multisensory events-the duration of attention maintenance, the accuracy of intersensory (audiovisual) matching, and the speed of shifting-for both social and nonsocial events, in the context of high and low competing visual stimulation. In Experiment 1, 2- to 5-year-old children (N = 36) received the MAAP and assessments of language and cognitive functioning. In Experiment 2 the procedure was streamlined and presented to 12-month-olds (N = 48). Both infants and children showed high levels of attention maintenance to social and nonsocial events, impaired attention maintenance and speed of shifting when competing stimulation was high, and significant intersensory matching. Children showed longer maintenance, faster shifting, and less impairment from competing stimulation than infants. In 2- to 5-year-old children, duration and accuracy were intercorrelated, showed increases with age, and predicted cognitive and language functioning. The MAAP opens the door to assessing developmental pathways between early attention patterns to audiovisual events and language, cognitive, and social development. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Gaze in a real-world social interaction: A dual eye-tracking study.

People communicate using verbal and non-verbal cues, including gaze cues. Gaze allocation can be influenced by social factors; however, most research on gaze cueing has not considered these factors. The presence of social roles was manipulated in a natural, everyday collaborative task while eye movements were measured. In pairs, participants worked together to make a cake. Half of the pairs were given roles ("Chef" or "Gatherer") and the other half were not. Across all participants we found, contrary to the results of static-image experiments, that participants spent very little time looking at each other, challenging the generalisability of the conclusions from lab-based paradigms. However, participants were more likely than not to look at their partner when receiving an instruction, highlighting the typical coordination of gaze cues and verbal communication in natural interactions. The mean duration of instances in which the partners looked at each other (partner gaze) was longer in the roles condition, and these participants were quicker to align their gaze with their partners (shared gaze). In addition, we found some indication that when hearing spoken instructions, listeners in the roles condition looked at the speaker more than listeners in the no roles condition. We conclude that social context can affect our gaze behaviour during a social interaction.

Individual objective versus subjective fixation disparity as a function of forced vergence.

Inaccuracy in the vergence eye position ("fixation disparity") can occur despite a fusion stimulus. When measured with eye trackers, this inaccuracy is referred to as "objective fixation disparity". It is a matter of debate whether objective fixation disparity can be estimated with a technically simple psycho-physical procedure, i.e. the perceived offset of aligned dichoptic nonius targets, referred to as "subjective fixation disparity". To investigate the relation between these two measures, simultaneous tests were made in far vision when placing prisms in front of the eyes (for a few seconds) in order to induce forced vergence, i.e. to vary the absolute disparity (from 1 deg divergent to 3.4 deg convergent). Frequent repeated measurements in 12 observers allowed for individual analyses. Generally, fixation disparity values and the effects of prisms were much smaller in the subjective than in the objective measures. Some observers differed systematically in the characteristics of the two types of prism-induced curves. Individual regressions showed that the subjective vs. objective slope was 8% on the average (with largest individual values of 18%). This suggests that sensory fusion shifts the visual direction of the (peripheral) binocular targets by the full amount of objective fixation disparity (since single vision was achieved); however, for the (central) monocular nonius lines this shift was more or less incomplete so that the dichoptic nonius targets indicated an individual percentage of objective fixation disparity. The subjective-to-objective ratio seems to be an individual characteristic of fixation disparity in terms of the amount and in terms of the effect of prism-induced forced vergence. Therefore, on the group level the subjective measures do not allow for a precise prediction of the objective measures.

Visual Fixation Assessment in Patients with Disorders of Consciousness Based on Brain-Computer Interface.

Visual fixation is an item in the visual function subscale of the Coma Recovery Scale-Revised (CRS-R). Sometimes clinicians using the behavioral scales find it difficult to detect because of the motor impairment in patients with disorders of consciousness (DOCs). Brain-computer interface (BCI) can be used to improve clinical assessment because it directly detects the brain response to an external stimulus in the absence of behavioral expression. In this study, we designed a BCI system to assist the visual fixation assessment of DOC patients. The results from 15 patients indicated that three showed visual fixation in both CRS-R and BCI assessments and one did not show such behavior in the CRS-R assessment but achieved significant online accuracy in the BCI assessment. The results revealed that electroencephalography-based BCI can detect the brain response for visual fixation. Therefore, the proposed BCI may provide a promising method for assisting behavioral assessment using the CRS-R.

Auditory noise increases the allocation of attention to the mouth, and the eyes pay the price: An eye-tracking study.

We investigated the effect of auditory noise added to speech on patterns of looking at faces in 40 toddlers. We hypothesised that noise would increase the difficulty of processing speech, making children allocate more attention to the mouth of the speaker to gain visual speech cues from mouth movements. We also hypothesised that this shift would cause a decrease in fixation time to the eyes, potentially decreasing the ability to monitor gaze. We found that adding noise increased the number of fixations to the mouth area, at the price of a decreased number of fixations to the eyes. Thus, to our knowledge, this is the first study demonstrating a mouth-eyes trade-off between attention allocated to social cues coming from the eyes and linguistic cues coming from the mouth. We also found that children with higher word recognition proficiency and higher average pupil response had an increased likelihood of fixating the mouth, compared to the eyes and the rest of the screen, indicating stronger motivation to decode the speech.

Face stimulus eliminates antisaccade-cost: gaze following is a different kind of arrow.

When a person suddenly looks in a certain direction, others seem to shift their attention to the same, looked-at, location. This common observation, that gaze-of-another seems to trigger reflexive shifts of attention within an observer, has been demonstrated in various studies. Yet just how reflexive it truly is, is an on-going controversy. Unlike most studies in which gaze cues were distractors in a cueing paradigm, the current study used gaze cues as triggers in a mixed pro- and anti-saccade task and a Posner-like discrimination task. In a set of two experiments, we investigated whether attention triggered by gaze-of-another differs from attention triggered by peripheral (exogenous) and arrow stimuli. In the first experiment, gaze cues resulted in slowed saccadic responses and in the elimination of the anti-saccade-cost associated with reflexive orienting. Pro-saccades triggered by peripheral cues had significantly fewer errors and shorter reaction times than anti-saccades. However, there was no significant difference between pro and anti-saccades triggered by gaze cues. Thus, counter to expectations, gaze did not produce reflexive shifts of overt attention. The second experiment showed that attention triggered by gaze cues is no different from attention triggered by biologically irrelevant arrow cues. They both eliminated the anti-saccade-cost and displayed prolonged reaction times. However, manual discrimination RTs showed no significant differences between gaze and peripheral cues. Together, these results suggest that neither gaze nor arrow cues trigger reflexive shifts of overt attention.

Application of eye tracking in medicine: A survey, research issues and challenges.

The performance and quality of medical procedures and treatments are inextricably linked to technological development. The application of more advanced techniques provides the opportunity to gain wider knowledge and deeper understanding of the human body and mind functioning. The eye tracking methods used to register eye movement to find the direction and targets of a person's gaze are well in line with the nature of the topic. By providing methods for capturing and processing images of the eye it has become possible not only to reveal abnormalities in eye functioning but also to conduct cognitive studies focused on learning about peoples' emotions and intentions. The usefulness of the application of eye tracking technology in medicine was proved in many research studies. The aim of this paper is to give an insight into those studies and the way they utilize eye imaging in medical applications. These studies were differentiated taking their purpose and experimental paradigms into account. Additionally, methods for eye movement visualization and metrics for its quantifying were presented. Apart from presenting the state of the art, the aim of the paper was also to point out possible applications of eye tracking in medicine that have not been exhaustively investigated yet, and are going to be a perspective long-term direction of research.

An Optimal Measurement of Fixation Disparity Using Ogle's Apparatus.

PURPOSE: Fixation disparity (FD) is a small misalignment of the eyes within the normal alignment when viewing under binocular condition. Ogle's apparatus measures FD. Standards of procedures vary, which may lead to different outcomes. METHODS: Students with normal ocular alignment, stereopsis ≤60 seconds of arc and visual acuity <0.1 logMAR, were included in this prospective comparative study. Four procedures (P1-P4) of measuring FD with Ogle's apparatus were performed with divergent placement of the line (P1 and P3), or the line moving from subjective zero (P1 and P2: prisms of ascending strength; P3 and P4: prisms alternating base in base out; combined and P4). Differences in the FD curve were determined by looking at point zero, motor fusion amplitude, and the degree of FD. RESULTS: Twenty-six participants were examined by these 4 procedures. Point zero showed a significant difference between P1-P2 (P=0.006) and P3-P4 (P=0.001). P1 and P3 indicated the highest point zero: median of -1 and -1.5 minutes of arc exodisparity. Motor fusion amplitude showed a significant difference between P1-P2 (P=0.037), P1-P3 (P=0.004), and P2-P4 (P=0.002). P1 revealed the highest motor fusion amplitude (median of 34Δ) and P4 the lowest amplitude (median of 28Δ). No significant differences were found in esodisparity. In exodisparity there was a significant difference comparing P1-P2 (P=0.000), P3-P4 (P=0.000), and P1-P3 (P=0.021). P1 gave the highest exodisparity (median 22 minutes of arc) and P4 the lowest (median 10 minutes of arc). CONCLUSION: Clinically relevant differences were found in exodisparity, mainly caused by difference in line shifting. Exodisparity was significantly lower, moving the line from subjective zero. The most accurate procedure is using prisms of ascending strength combined with divergent placement of the line (P1). These findings standardize a reliable procedure of measuring the FD curve for clinical use. Patients will not be misdiagnosed with reduced FD.

Computing eye gaze metrics for the automatic assessment of radiographer performance during X-ray image interpretation.

AIM: To investigate image interpretation performance by diagnostic radiography students, diagnostic radiographers and reporting radiographers by computing eye gaze metrics using eye tracking technology. METHODS: Three groups of participants were studied during their interpretation of 8 digital radiographic images including the axial and appendicular skeleton, and chest (prevalence of normal images was 12.5%). A total of 464 image interpretations were collected. Participants consisted of 21 radiography students, 19 qualified radiographers and 18 qualified reporting radiographers who were further qualified to report on the musculoskeletal (MSK) system. OUTCOME MEASURES: Eye tracking data was collected using the Tobii X60 eye tracker and subsequently eye gaze metrics were computed. Voice recordings, confidence levels and diagnoses provided a clear demonstration of the image interpretation and the cognitive processes undertaken by each participant. A questionnaire afforded the participants an opportunity to offer information on their experience in image interpretation and their opinion on the eye tracking technology. RESULTS: Reporting radiographers demonstrated a 15% greater accuracy rate (p≤0.001), were more confident (p≤0.001) and took a mean of 2.4s longer to clinically decide on all features compared to students. Reporting radiographers also had a 15% greater accuracy rate (p≤0.001), were more confident (p≤0.001) and took longer to clinically decide on an image diagnosis (p=0.02) than radiographers. Reporting radiographers had a greater mean fixation duration (p=0.01), mean fixation count (p=0.04) and mean visit count (p=0.04) within the areas of pathology compared to students. Eye tracking patterns, presented within heat maps, were a good reflection of group expertise and search strategies. Eye gaze metrics such as time to first fixate, fixation count, fixation duration and visit count within the areas of pathology were indicative of the radiographer's competency. CONCLUSION: The accuracy and confidence of each group could be reflected in the variability of their eye tracking heat maps. Participants' thoughts and decisions were quantified using the eye tracking data. Eye tracking metrics also reflected the different search strategies that each group of participants adopted during their image interpretations. This is the first study to use eye tracking technology to assess image interpretation skills between various groups of different levels of experience in radiography, especially on a combination of the MSK system, chest cavity and a variety of pathologies.