Eye tracking: empirical foundations for a minimal reporting guideline.

In this paper, we present a review of how the various aspects of any study using an eye tracker (such as the instrument, methodology, environment, participant, etc.) affect the quality of the recorded eye-tracking data and the obtained eye-movement and gaze measures. We take this review to represent the empirical foundation for reporting guidelines of any study involving an eye tracker. We compare this empirical foundation to five existing reporting guidelines and to a database of 207 published eye-tracking studies. We find that reporting guidelines vary substantially and do not match with actual reporting practices. We end by deriving a minimal, flexible reporting guideline based on empirical research (Section "An empirically based minimal reporting guideline").

The Use of Video Laryngoscopy Did Not Lead to Greater First-Pass or Overall Success Rates Compared to Direct Laryngoscopy in Pediatric Intubation in a Helicopter Emergency Medical Service.

OBJECTIVE: We hypothesized that video laryngoscopy (VL) would significantly increase the first attempt and final success rates over direct laryngoscopy (DL) in helicopter emergency medical services. METHODS: This was a study of an emergency medical service in the Midwestern United States. Pediatric patients (age < 18 years) transported between January 1, 2010, and July 31, 2016, with an attempted intubation were identified. Demographics (age group and sex), first-pass success (FPS), and total attempts by intubation type were abstracted and compared with a historical control. RESULTS: Fifty-five pediatric patient runs were abstracted (DL: n = 28, VL: n = 27). There were no significant differences between the DL and VL groups based on sex (DL: 54% male, VL: 70% male; P = .200) or age group (P = .239). Analyses of FPS between DL and VL showed no difference (DL: 82.1% success vs. VL: 70.4% success; P = .304). There was no difference for final success rate between DL and VL (DL: 85.7%, VL: 96.3%; P = .172). A significantly larger number of difficult airways were reported in the VL group (37.0%) compared with DL (7.1%, P = .007). CONCLUSION: VL did not improve FPS over DL nor did it improve the final endotracheal intubation success rate over DL. The VL group had more airways reported as being difficult by the flight crew than the DL group.

Visual input to the left versus right eye yields differences in face preferences in 3-month-old infants.

From birth, infants prefer looking at faces over scrambled faces. This face input is important for the development of face processing: individuals who experienced early visual deprivation due to congenital cataracts have long-lasting face processing deficits. Interestingly, the deficits are eye-specific such that left eye cataracts disrupt the development of face processing, whereas right eye cataracts do not. This raises the question of whether infant face preferences are driven primarily by faces observed through the left eye. To investigate this, we presented 3-month-old infants with intact faces paired with scrambled faces. Infants viewed the moving stimuli binocularly, only with their left eye, or only with their right eye. Infants viewing stimuli binocularly or with only the left eye spent significantly more time looking at intact faces than scrambled faces, but this effect was equivocal in infants viewing stimuli through only their right eye. Infants in the binocular group had the greatest preference for faces, and this preference was greater than the right eye group's preference for faces. The left eye group's preference for faces was not statistically different from the other two groups' preference for faces, but additional analyses revealed a correlation between preference for faces and age for the right eye group only, indicating that preference for faces seen with the right eye increase from 3 to 4 months of age. These results indicate that the left eye plays a special role in face processing at, or before 3 months of age, but a preference for faces through the right eye emerges soon after.

Impaired face detection may explain some but not all cases of developmental prosopagnosia.

Developmental prosopagnosia (DP) is defined by severe face recognition difficulties due to the failure to develop the visual mechanisms for processing faces. The two-process theory of face recognition (Morton & Johnson, 1991) implies that DP could result from a failure of an innate face detection system; this failure could prevent an individual from then tuning higher-level processes for face recognition (Johnson, 2005). Work with adults indicates that some individuals with DP have normal face detection whereas others are impaired. However, face detection has not been addressed in children with DP, even though their results may be especially informative because they have had less opportunity to develop strategies that could mask detection deficits. We tested the face detection abilities of seven children with DP. Four were impaired at face detection to some degree (i.e. abnormally slow, or failed to find faces) while the remaining three children had normal face detection. Hence, the cases with impaired detection are consistent with the two-process account suggesting that DP could result from a failure of face detection. However, the cases with normal detection implicate a higher-level origin. The dissociation between normal face detection and impaired identity perception also indicates that these abilities depend on different neurocognitive processes.

Temporal dynamics of the face familiarity effect: bootstrap analysis of single-subject event-related potential data.

Prior event-related potential studies using group statistics within a priori selected time windows have yielded conflicting results about familiarity effects in face processing. Our goal was to evaluate the temporal dynamics of the familiarity effect at all time points at the single-subject level. Ten subjects were shown faces of anonymous people or celebrities. Individual results were analysed using a point-by-point bootstrap analysis. While familiarity effects were less consistent at later epochs, all subjects showed them between 130 and 195 ms in occipitotemporal electrodes. However, the relation between the time course of familiarity effects and the peak latency of the N170 was variable. We concluded that familiarity effects between 130 and 195 ms are robust and can be shown in single subjects. The variability of their relation to the timing of the N170 potential may lead to underestimation of familiarity effects in studies that use group-based statistics.

Program evaluation of cognitive behavioral therapy in burn survivors.

Mental health is a component of care that should be addressed for burn patients while they are hospitalized. Unfortunately, dedicated burn psychotherapists are rare in burn centers in the United States (US), and it can take months for patients to be seen by a mental health professional after referral. Our burn center has a dedicated licensed clinical social worker who sees patients within two business days of referral. She uses cognitive behavioral therapy (CBT), which is designed to alleviate symptoms of anxiety, depression, and acute stress by modifying the individual's maladaptive thoughts. To evaluate the timely use of CBT as a treatment for depression in burn patients, we measured depressive symptoms before and after psychotherapy. Burn clinic nurses administered the Patient Health Questionnaire (PHQ-9) depression screener as part of standard care. We computed difference scores to determine change in PHQ-9 scores at both group and individual levels. At a group level, psychotherapy significantly improved symptoms of depression, indicated by a decreased mean PHQ-9 score. On an individual level, half of the patients (50.7%) experienced a meaningful improvement in their symptoms, indicated by a change in their PHQ-9 depression category, while 35.6% showed no change. Although it was not an effective solution for all patients in this study, timely use of CBT could be an important component of burn care for many and should be considered as part of standard care in burn centers across the US.

Impact of repeated sportive chokes on carotid intima media thickness and brain injury biomarkers in grappling athletes.

PURPOSE: Vascular neck compression techniques, referred to as 'chokes' in combat sports, reduce cerebral perfusion, causing loss of consciousness or voluntary submission by the choked athlete. Despite these chokes happening millions of times yearly around the world, there is scant research on their long-term effects. This pilot study evaluated whether repeated choking in submission grappling impacts the carotid intima media thickness (CIMT) and brain injury biomarkers (NFL, hGFAP, t-Tau, and UCH-L1). METHODS: Participants (n = 39, 29 male; ages 27-60 years) were assigned to one of two study arms: Grapplers (n = 20, 15 male) and 19 age/sex/body size matched controls. Grapplers had been exposed to >500 choke events while training for >5 years in a choke-inclusive sport. Exclusion criteria were recent TBI or deficits from a past TBI or stroke. Bilateral ultrasound measurement of the CIMT was performed, and blood was collected for quantitative analysis of four brain injury markers. Subgroup analyses were performed within the Grappler group to account for blunt head trauma as a possible confounder. RESULTS: There was no overall difference in CIMT measurements between Grapplers (mean 0.55 mm, SD 0.07) and Controls (mean 0.57 mm, SD 0.10) p = 0.498 [95% CI -0.04-0.08], nor were there CIMT differences between Grappler subgroups of blunt Trauma and No-Trauma. There were no significant differences in any biomarkers comparing Grapplers and Controls or comparing Grappler subgroups of Trauma and No-Trauma. CONCLUSION: This study found no significant difference in CIMT and serum brain injury biomarkers between controls and grapplers with extensive transient choke experience, nor between grapplers with extensive past blunt head trauma and those without.

Eyeing the eyes in social scenes: Evidence for top-down control of stimulus selection in simultanagnosia.

Simultanagnosia is a disorder of visual attention resulting from bilateral parieto-occipital lesions. Healthy individuals look at eyes to infer people's attentional states, but simultanagnosics allocate abnormally few fixations to eyes in scenes. It is unclear why simultanagnosics fail to fixate eyes, but it might reflect that they are (a) unable to locate and fixate them, or (b) do not prioritize attentional states. We compared eye movements of simultanagnosic G.B. to those of healthy subjects viewing scenes normally or through a restricted window of vision. They described scenes and explicitly inferred attentional states of people in scenes. G.B. and subjects viewing scenes through a restricted window made few fixations on eyes when describing scenes, yet increased fixations on eyes when inferring attention. Thus G.B. understands that eyes are important for inferring attentional states and can exert top-down control to seek out and process the gaze of others when attentional states are of interest.

Developmental prosopagnosia in childhood.

Developmental prosopagnosia (DP) is defined by severe face recognition problems resulting from a failure to develop the necessary visual mechanisms for processing faces. While there is a growing literature on DP in adults, little has been done to study this disorder in children. The profound impact of abnormal face perception on social functioning and the general lack of awareness of childhood DP can result in severe social and psychological consequences for children. This review discusses possible aetiologies of DP and summarizes the few cases of childhood DP that have been reported. It also outlines key objectives for the growth of this emerging research area and special considerations for studying DP in children. With clear goals and concerted efforts, the study of DP in childhood will be an exciting avenue for enhancing our understanding of normal and abnormal face perception for all age groups.

Simulating simultanagnosia: spatially constricted vision mimics local capture and the global processing deficit.

Patients with simultanagnosia, which is a component of Bálint syndrome, have a restricted spatial window of visual attention and cannot see more than one object at a time. As a result, these patients see the world in a piecemeal fashion, seeing the local components of objects or scenes at the expense of the global picture. To directly test the relationship between the restriction of the attentional window in simultanagnosia and patients' difficulty with global-level processing, we used a gaze-contingent display to create a literal restriction of vision for healthy participants while they performed a global/local identification task. Participants in this viewing condition were instructed to identify the global and local aspects of hierarchical letter stimuli of different sizes and densities. They performed well at the local identification task, and their patterns of inaccuracies for the global level task were highly similar to the pattern of inaccuracies typically seen with simultanagnosic patients. This suggests that a restricted spatial area of visual processing, combined with normal limits to visual processing, can lead to difficulties with global-level perception.

Event-related potential evidence for a dual-locus model of global/local processing.

We investigated the perceptual time course of global/local processing using event-related potentials (ERPs). Participants discriminated the global or local level of hierarchical letters of different sizes and densities. Participants were faster to discriminate the local level of large/sparse letters and the global level of small/dense letters. This was mirrored in early ERP components: The N1/N2 had smaller peak amplitudes when participants made discriminations at the level that took precedence. Only global discriminations for large/sparse letters led to amplitude enhancement of the later P3 component, suggesting that additional attention-demanding processes are involved in discriminating the global level of these stimuli. Our findings suggest a dual-locus time course for global/local processing: (a) Level precedence occurs early in visual processing; (b) extra processing is required at a later stage, but only for global discriminations of large, sparse, stimuli, which may require additional attentional resources for active grouping.

Machine learning accurately classifies age of toddlers based on eye tracking.

How people extract visual information from complex scenes provides important information about cognitive processes. Eye tracking studies that have used naturalistic, rather than highly controlled experimental stimuli, reveal that variability in looking behavior is determined by bottom-up image properties such as intensity, color, and orientation, top-down factors such as task instructions and semantic information, and individual differences in genetics, cognitive function and social functioning. These differences are often revealed using areas of interest that are chosen by the experimenter or other human observers. In contrast, we adopted a data-driven approach by using machine learning (Support Vector Machine (SVM) and Deep Learning (DL)) to elucidate factors that contribute to age-related variability in gaze patterns. These models classified the infants by age with a high degree of accuracy, and identified meaningful features distinguishing the age groups. Our results demonstrate that machine learning is an effective tool for understanding how looking patterns vary according to age, providing insight into how toddlers allocate attention and how that changes with development. This sensitivity for detecting differences in exploratory gaze behavior in toddlers highlights the utility of machine learning for characterizing a variety of developmental capacities.

Rapid face orienting in infants and school-age children with and without autism: Exploring measurement invariance in eye-tracking.

Questions concerning the ontogenetic stability of autism have recently received increased attention as long-term longitudinal studies have appeared in the literature. Most experimental measures are designed for specific ages and functioning levels, yet developing experimental tasks appropriate for a wide range of ages and functioning levels is critical for future long-term longitudinal studies, and treatment studies implemented at different ages. Accordingly, we designed an eye-tracking task to measure preferential orienting to facial features and implemented it with groups of participants with varying levels of functioning: infants, and school-age children with and without autism. All groups fixated eyes first, revealing an early and stable orienting bias. This indicates common bias towards the eyes across participants regardless of age or diagnosis. We also demonstrate that this eye-tracking task can be used with diverse populations who range in age and cognitive functioning. Our developmental approach has conceptual implications for future work focused on task development and particularly new experimental measures that offer measurement equivalence across broad age ranges, intellectual functioning and verbal abilities.

An Examination of Recording Accuracy and Precision From Eye Tracking Data From Toddlerhood to Adulthood.

The quantitative assessment of eye tracking data quality is critical for ensuring accuracy and precision of gaze position measurements. However, researchers often report the eye tracker's optimal manufacturer's specifications rather than empirical data about the accuracy and precision of the eye tracking data being presented. Indeed, a recent report indicates that less than half of eye tracking researchers surveyed take the eye tracker's accuracy into account when determining areas of interest for analysis, an oversight that could impact the validity of reported results and conclusions. Accordingly, we designed a calibration verification protocol to augment independent quality assessment of eye tracking data and examined whether accuracy and precision varied between three age groups of participants. We also examined the degree to which our externally quantified quality assurance metrics aligned with those reported by the manufacturer. We collected data in standard laboratory conditions to demonstrate our method, to illustrate how data quality can vary with participant age, and to give a simple example of the degree to which data quality can differ from manufacturer reported values. In the sample data we collected, accuracy for adults was within the range advertised by the manufacturer, but for school-aged children, accuracy and precision measures were outside this range. Data from toddlers were less accurate and less precise than data from adults. Based on an a priori inclusion criterion, we determined that we could exclude approximately 20% of toddler participants for poor calibration quality quantified using our calibration assessment protocol. We recommend implementing and reporting quality assessment protocols for any eye tracking tasks with participants of any age or developmental ability. We conclude with general observations about our data, recommendations for what factors to consider when establishing data inclusion criteria, and suggestions for stimulus design that can help accommodate variability in calibration. The methods outlined here may be particularly useful for developmental psychologists who use eye tracking as a tool, but who are not experts in eye tracking per se. The calibration verification stimuli and data processing scripts that we developed, along with step-by-step instructions, are freely available for other researchers.

Using High Frequency Transcranial Random Noise Stimulation to Modulate Face Memory Performance in Younger and Older Adults: Lessons Learnt From Mixed Findings.

High-frequency transcranial random noise stimulation (tRNS) has been shown to improve a range of cognitive and perceptual abilities. Here we sought to examine the effects of a single session of tRNS targeted at the ventrolateral prefrontal cortices (VLPFC) on face memory in younger and older adults. To do so, we conducted three experiments. In Experiment 1, we found that younger adults receiving active tRNS outperformed those receiving sham stimulation (i.e., using a between-participant factor for stimulation condition; Experiment 1). This effect was not observed for object memory (car memory) in younger adults (Experiment 2), indicating that the effect is not a general memory effect. In Experiment 3, we sought to replicate the effects of Experiment 1 using a different design (within-participant factor of stimulation - active or sham tRNS to the same individual) and to extend the study by including older adult participants. In contrast to Experiment 1, we found that active tRNS relative to sham tRNS reduced face memory performance in both younger and older adults. We also found that the degree of decline in performance in the active tRNS relative to sham tRNS condition was predicted by baseline ability, with higher performing participants showing the largest decreases in performance. Overall, the results indicate that tRNS to the VLPFC modulates face memory, but that there may be performance and protocol specific moderators of this effect. We discuss these findings in the context of the broader literature showing the importance of individual variation in the outcome of non-invasive brain stimulation intervention approaches. We conclude that while tRNS may have potential as an intervention approach, generalizing from single experiment studies to wide application is risky and caution should be adopted in interpreting findings.

Seeing trees OR seeing forests in simultanagnosia: attentional capture can be local or global.

Patients with simultanagnosia often demonstrate 'local capture', meaning that they identify only the local elements of stimuli that contain a hierarchy of both local and global structures. Recent studies, however, have found that these patients may implicitly process the global form. We examined the general applicability of the concept of local capture, and specifically whether the global level of stimuli can be explicitly reported by patients with simultanagnosia. We tested a patient with simultanagnosia with globally biased stimuli such as hierarchical Arcimboldo faces and small, dense Navon letters. With Arcimboldo faces our patient often reported only the face and not the local elements--the first demonstration of global rather than local capture. With Navon letters, the patient's ability to report the global letter varied with stimulus density and inversely with stimulus size, so that local capture was found only with large and sparse stimuli. With both faces and letters, the likelihood of global capture by the patient was related to the ease of global reporting in controls, as indexed by their reaction times. This suggests that the patient's global perception is influenced by the same factors operating in healthy individuals. We conclude that attentional capture in simultanagnosia can be either global or local. Capture likely occurs because of a pathological restriction and/or rigidity of attention, but the type of capture depends upon the competitive balance between global and local salience.

Face-specific and domain-general visual processing deficits in children with developmental prosopagnosia.

Evidence suggests that face and object recognition depend on distinct neural circuitry within the visual system. Work with adults with developmental prosopagnosia (DP) demonstrates that some individuals have preserved object recognition despite severe face recognition deficits. This face selectivity in adults with DP indicates that face- and object-processing systems can develop independently, but it is unclear at what point in development these mechanisms are separable. Determining when individuals with DP first show dissociations between faces and objects is one means to address this question. In the current study, we investigated face and object processing in six children with DP (5-12-years-old). Each child was assessed with one face perception test, two different face memory tests, and two object memory tests that were matched to the face memory tests in format and difficulty. Scores from the DP children on the matched face and object tasks were compared to within-subject data from age-matched controls. Four of the six DP children, including the 5-year-old, showed evidence of face-specific deficits, while one child appeared to have more general visual-processing deficits. The remaining child had inconsistent results. The presence of face-specific deficits in children with DP suggests that face and object perception depend on dissociable processes in childhood.

Concurrent development of facial identity and expression discrimination.

Facial identity and facial expression processing both appear to follow a protracted developmental trajectory, yet these trajectories have been studied independently and have not been directly compared. Here we investigated whether these processes develop at the same or different rates using matched identity and expression discrimination tasks. The Identity task begins with a target face that is a morph between two identities (Identity A/Identity B). After a brief delay, the target face is replaced by two choice faces: 100% Identity A and 100% Identity B. Children 5-12-years-old were asked to pick the choice face that is most similar to the target identity. The Expression task is matched in format and difficulty to the Identity task, except the targets are morphs between two expressions (Angry/Happy, or Disgust/Surprise). The same children were asked to pick the choice face with the expression that is most similar to the target expression. There were significant effects of age, with performance improving (becoming more accurate and faster) on both tasks with increasing age. Accuracy and reaction times were not significantly different across tasks and there was no significant Age x Task interaction. Thus, facial identity and facial expression discrimination appear to develop at a similar rate, with comparable improvement on both tasks from age five to twelve. Because our tasks are so closely matched in format and difficulty, they may prove useful for testing face identity and face expression processing in special populations, such as autism or prosopagnosia, where one of these abilities might be impaired.

Guidelines for studying developmental prosopagnosia in adults and children.

Developmental prosopagnosia (DP) is a neurodevelopmental condition characterized by severe face identity recognition problems that results from a failure to develop the mechanisms necessary for adequate face processing (Duchaine BC, Nakayama K. Developmental prosopagnosia: a window to content-specific face processing. Curr Opin Neurobiol 2006, 16:166-173.). It occurs in children and adults with normal visual acuity, and without intellectual impairments or known brain injuries. Given the importance of face recognition in daily life, and the detrimental effects of impaired face recognition, DP is an important area of study. Yet conventions for classifying individuals as DP for research purposes are poorly defined. In this focus paper, we discuss: (1) criteria for an operational definition of DP; 2) tests of face recognition and conventions for classifying individuals as DP; and 3) important considerations regarding common associations and dissociations, and cognitive heterogeneity in DP. We also highlight issues unique to studying DP in children, a relatively new endeavor that is proving to be an important complement to the work with adults. Ultimately, we hope to identify challenges researchers face when studying DP, and offer guidelines for others to consider when embarking on their own research pursuits on the topic. For further resources related to this article, please visit the WIREs website.