Visual Gaze Research Articles

Objects in the peripheral visual field influence gaze location in natural vision

In everyday behavior there are multiple competing demands for gaze; for instance, walking along a sidewalk requires paying attention to the path while avoiding other pedestrians. Therefore, humans make numerous fixations to satisfy their behavioral goals. One attempt to explore suitable strategies of gaze allocation for natural situations was made by Sprague, Ballard and Robinson (2007), whose computational model predicts human visuo-motor behavior based on intrinsic reward and uncertainty. Their model presupposes that specific visual information is acquired from the currently fixated object only. However, evidence that peripheral objects affect gaze position by drawing it towards the center of gravity of target ensembles (Findlay, 1982; Vishwanath & Kowler, 2003) challenges this premise. Since the influence of peripheral information for natural vision remains largely unexplored, we investigated whether gaze targeting is biased towards peripheral objects in naturalistic tasks. Using a Virtual Reality environment, the fixations of 12 participants were examined while they walked through a virtual room with objects of two different colors that were designated targets or obstacles. The subjects were instructed to either collect targets, to avoid obstacles or to do both tasks simultaneously. For situations in which one of two visible objects was fixated, subjects' gaze positions were biased more often towards the non-fixated object (72.6%) than away from it (27.4%). Moreover, the gaze position tended to be drawn more frequently towards the neighboring object when this neighbor was relevant to the current task than when it was task-irrelevant. These results indicate that information from peripheral objects affect human gaze targeting in natural vision. Furthermore, the effect of the neighbor's task-relevance - and therefore of intrinsic reward - suggests that in a given fixation subjects might gather information from the peripheral visual field to accomplish a current set of goals at once. Meeting abstract presented at VSS 2015. Language: en

Investigation and modeling of visual fatigue caused by S3D content using eye-tracking

3D has been one of the most important technologies of the last decade having an exponential progression. Nevertheless, several problems such as visual discomfort and visual fatigue have slowed its progression for homes. This factor decreases significantly the overall quality of experience from watching 3D content and reduces the level of satisfaction of a user. This study explores the accumulation of visual fatigue when watching 3D video in close to real-life conditions. In order to obtain more information about visual discomfort, an hour of eye-tracking experiments have been conducted. Investigations have been made by analyzing information provided both by users through questionnaires and visual gaze characteristics recording. Obtained results are compared to data produced when watching 2D. The deep statistical analysis showed that time and video content have an influence on video fatigue accumulation and visual functions. With respect to the obtained results, a model has been proposed based on video characteristics (motion activity, disparity range and changes) and the previous state of visual fatigue.

Combining eye tracking and pupillary dilation analysis to identify Website Key Objects

Identifying the salient zones from Web interfaces, namely the Website Key Objects, is an essential part of the personalization process that current Web systems perform to increase user engagement. While several techniques have been proposed, most of them are focused on the use of Web usage logs. Only recently has the use of data from users׳ biological responses emerged as an alternative to enrich the analysis. In this work, a model is proposed to identify Website Key Objects that not only takes into account visual gaze activity, such as fixation time, but also the impact of pupil dilation. Our main hypothesis is that there is a strong relationship in terms of the pupil dynamics and the Web user preferences on a Web page. An empirical study was conducted on a real Website, from which the navigational activity of 23 subjects was captured using an eye tracking device. Results showed that the inclusion of pupillary activity, although not conclusively, allows us to extract a more robust Web Object classification, achieving a 14% increment in the overall accuracy.

On visual gaze tracking based on a single low cost camera

Gaze tracking technologies provide an unconventional way of human–computer interaction, envisaged to advance practical applications and industrial products in a multitude of fields. The success of such systems depends on selecting the best calibration setup and image features that correspond to a person׳s line of sight. The purpose of this study is to estimate eye gaze from a single, low cost web-cam, under natural lighting. Facial traits are extracted from the sensory data, from which distance vectors related to gaze are derived. Different experimental setups are studied to evaluate the robustness of the proposed method with respect to various calibration setups, camera position and head movements. The use of new additional features improves the modeling of the subtle eye movements in the vertical direction, while a new calibration setup is proposed that further enhances the performance. The results demonstrate that the proposed framework is able to track gaze with good accuracy, consolidating the use of inexpensive equipment and techniques towards an ever-expanding range of gaze tracking applications.

Aurally aided visual search performance for stationary and walking listeners

One of the most important functions of spatial hearing is to facilitate the rapid shift of visual gaze in the direction of newly detected sound sources that might represent potential targets or threats in our environment. Some of the most dangerous threats can emerge when listeners are walking, so it is useful to know what impact walking might have on audiovisual target detection and identification in complex scenes. This study used a virtual environment consisting of a motorized treadmill surrounded by a 180° projection screen mounted in front of a 64-loudspeaker array to evaluate how quickly participants were able to detect a visual target displayed in the presence of multiple distracters. The distracters were small clusters containing 2 or 4 dots, and the target was a small cluster containing 1 or 3 dots that was presented from the same location as a pulsed broadband noise. The task was to find the target as quickly as possible and press a button to indicate if it had 1 or 3 dots. Data were also collected in an auditory localization condition that required listeners to move a cursor to the location of the sound source and a visual-only condition that required participants to perform the visual search task with no auditory cue. The results show that target identification times were generally reduced when the listener was walking, suggesting that the increased motor activation caused by walking may enhance the ability to perform audiovisual searches. [Research Supported by DoD PHTBI award (W81XWH-12-2-0068).]

Visual guidance during bicycle steering through narrow lanes: A study in children

Recently, Vansteenkiste et al. (2013) explored how visual behaviour guides bicycle steering when cycling at different speeds through 15m long lanes of 10, 25 and 40cm wide. Participants were found to shift their gaze direction towards the end of the lanes at higher speeds, towards the near pathway on narrow lanes and more towards irrelevant areas on wider lanes. To investigate to what extent young learner bicyclists adapt their visual behaviour in a similar way as adults, the experiment was repeated with seven eight-year-old children, and results were compared to the adult data. Children were found to cycle slower through narrow lanes than adults. However, with increasing lane width and cycling speed, children made the same shifts of visual gaze direction as the adults. These results suggest that for a simple precision steering task, children are able to adopt a similar visual-motor strategy as adults, provided that they cycle at their own pace.

The effect of computer-aided detection markers on visual search and reader performance during concurrent reading of CT colonography.

We aimed to identify the effect of computer-aided detection (CAD) on visual search and performance in CT Colonography (CTC) of inexperienced and experienced readers. Fifteen endoluminal CTC examinations were recorded, each with one polyp, and two videos were generated, one with and one without a CAD mark. Forty-two readers (17 experienced, 25 inexperienced) interpreted the videos during infrared visual search recording. CAD markers and polyps were treated as regions of interest in data processing. This multi-reader, multi-case study was analysed using multilevel modelling. CAD drew readers' attention to polyps faster, accelerating identification times: median 'time to first pursuit' was 0.48 s (IQR 0.27 to 0.87 s) with CAD, versus 0.58 s (IQR 0.35 to 1.06 s) without. For inexperienced readers, CAD also held visual attention for longer. All visual search metrics used to assess visual gaze behaviour demonstrated statistically significant differences when "with" and "without" CAD were compared. A significant increase in the number of correct polyp identifications across all readers was seen with CAD (74 % without CAD, 87 % with CAD; p < 0.001). CAD significantly alters visual search and polyp identification in readers viewing three-dimensional endoluminal CTC. For polyp and CAD marker pursuit times, CAD generally exerted a larger effect on inexperienced readers. • Visual gaze is attracted by computer-assisted detection (CAD) marks on polyps • Inexperienced readers' gaze is affected more by CAD than experienced readers. • CAD marks could mean that the unannotated endoluminal surface is relatively neglected. • Correct polyp identification is increased significantly by CAD.

On the possible roles of microsaccades and drifts in visual perception

During natural viewing large saccades shift the visual gaze from one target to another every few hundreds of milliseconds. The role of microsaccades (MSs), small saccades that show up during long fixations, is still debated. A major debate is whether MSs are used to redirect the visual gaze to a new location or to encode visual information through their movement. We argue that these two functions cannot be optimized simultaneously and present several pieces of evidence suggesting that MSs redirect the visual gaze and that the visual details are sampled and encoded by ocular drifts. We show that drift movements are indeed suitable for visual encoding. Yet, it is not clear to what extent drift movements are controlled by the visual system, and to what extent they interact with saccadic movements. We analyze several possible control schemes for saccadic and drift movements and propose experiments that can discriminate between them. We present the results of preliminary analyses of existing data as a sanity check to the testability of our predictions.

A New Approach for Body Balance of a Humanoid Robot

In humans, the vestibular system along with other sensory and motor systems is responsible for three cognitive functions that support mobility. First, is responsible for the balance of the body. Second, it allows humans to maintain the head stabilized. Finally, whenever the body or head are in motion, it maintains the visual gaze on a desired target. These tasks are performed using an array of sensors that are located within the inner ear. This paper describes the design and implementation of a synthetic model of the human vestibular system. The model is based on neurophysiological evidence, which makes it necessary to model all of the neural and physical components involved in the balance of the body. The model includes a component for each of the sensors, cortical and subcortical neural structures. It also defines and generates the necessary motor output signals. The proposed model was connected to a Bioloid® Premium humanoid robot to simulate the motor output and the proprioceptive inputs. The physical tests resulted inconclusive due to the fact that the controller on the robot was incapable of handling the necessary information for the tests. However, even though the results were not the desired, the communication between the sensors and the architecture, as well as the processing inside the architecture satisfied all of the authors' expectations.

Negotiated control between the manual and visual systems for visually guided hand reaching movements.

BackgroundControl of reaching movements for manual work, vehicle operation, or interactions with manual interfaces requires concurrent gaze control for visual guidance of the hand. We hypothesize that reaching movements are based on negotiated strategies to resolve possible conflicting demands placed on body segments shared by the visual (gaze) and manual (hand) control systems. Further, we hypothesize that a multiplicity of possible spatial configurations (redundancy) in a movement system enables a resolution of conflicting demands that does not require sacrificing the goals of the two systems.MethodsThe simultaneous control of manual reach and gaze during seated reaching movements was simulated by solving an inverse kinematics model wherein joint trajectories were estimated from a set of recorded hand and head movements. A secondary objective function, termed negotiation function, was introduced to describe a means for the manual reach and gaze directing systems to balance independent goals against (possibly competing) demands for shared resources, namely the torso movement. For both systems, the trade-off may be resolved without sacrificing goal achievement by taking advantage of redundant degrees of freedom. Estimated joint trajectories were then compared to joint movement recordings from ten participants. Joint angles were predicted with and without the negotiation function in place, and model accuracy was determined using the root-mean-square errors (RMSEs) and differences between estimated and recorded joint angles.ResultsThe prediction accuracy was generally improved when negotiation was included: the negotiated control reduced RMSE by 16% and 30% on average when compared to the systems with only manual or visual control, respectively. Furthermore, the RMSE in the negotiated control system tended to improve with torso movement amplitude.ConclusionsThe proposed model describes how multiple systems cooperate to perform goal-directed human movements when those movements draw upon shared resources. Allocation of shared resources can be undertaken by a negotiation process that is aware of redundancies and the existence of multiple solutions within the individual systems.

Oculogyric crisis in a patient taking metoclopramide

Oculogyric crisis is an acute dystonic reaction of the ocular muscles characterized by bilateral dystonic elevation of visual gaze lasting from seconds to hours. This reaction is most commonly explained as an adverse reaction to drugs such as antiemetics, antipsychotics, antidepressants, antiepileptics, and antimalarials. Although the incidence of metoclopramide-induced acute dystonic reactions has been reported as 25% in children, there have been few published cases on oculogyric crisis in general. It is important to be able to recognize this ocular side effect because, without a thorough patient history, symptoms can be confused with other diseases such as versive seizures, paroxysmal tonic upward gaze, and encephalopathy. In this paper, we report a case of oculogyric crisis induced by metoclopramide.

Congenital Muscular Torticollis and Positional Plagiocephaly

Congenital Muscular Torticollis and Positional Plagiocephaly

Congenital Muscular Torticollis and Positional Plagiocephaly

On the basis of observational studies, child health practitioners in primary care settings should consider the diagnosis of congenital muscular torticollis (CMT)in infants with risk factors from birth history for intrauterine malpositioning or constraint (C). On the basis of observational studies, CMT is often associated with other conditions, including positional plagiocephaly and gross motor delays from weakened truncal muscles and/or lack of head control in early infancy (C). On the basis of observational studies, child health practitioners should counsel parents that infants should be on their stomachs frequently whenever they are awake and under direct adult supervision to develop their prone motor skills (C). On the basis of consensus, early identification of CMT(with or without positional plagiocephaly) and prompt referral to a physical therapist experienced in the treatment of CMT should be considered to avoid more costly or invasive treatments, such as cranial orthoses or surgery (D).

Different types of sounds influence gaze differently in videos

This paper presents an analysis of the effect of different types of sounds on visual gaze when a person is looking freely at videos, which would be helpful to predict eye position. In order to test the effect of sound, an audio-visual experiment was designed with two groups of participants, with audio-visual (AV) and visual (V) conditions. By using statistical tools, we analyzed the difference between eye position of participants with AV and V conditions. We observed that the effect of sound is different depending on the kind of sound, and that the classes with human voice (i.e. speech, singer, human noise and singers) have the greatest effect. Furthermore, the results of the distance between sound source and eye position of the group with AV condition, suggested that only particular types of sound attract human eye position to the sound source. Finally, an analysis of the fixation duration between AV and V conditions showed that participants with AV condition move eyes more frequently than those with V condition.

The role of controlled attention on recall in major depression

Information processing biases are hallmark features of major depressive disorder (MDD). Depressed individuals display biased memory and attention for negative material. Given that memory is highly dependent on attention for initial encoding, understanding the interplay of these processes may provide important insight into mechanisms that produce memory biases in depression. In particular, attentional control—the ability to selectively attend to task-relevant information by both inhibiting the processing of irrelevant information and disengaging attention from irrelevant material—may be one area of impairment in MDD. In the current study, clinically depressed (MDD: n = 15) and never depressed (non-MDD: n = 22) participants' line of visual gaze was assessed while participants viewed positive and negative word pairs. For each word pair, participants were instructed to attend to one word (target) and ignore one word (distracter). Free recall of study stimuli was then assessed. Depressed individuals displayed greater recall of negatively valenced target words following the task. Although there were no group differences in attentional control in the context of negative words, attention to negative targets mediated the relationship between depression status and recall of negative words. Results suggest a stronger link between attention and memory for negative material in MDD.

Eye-Catching Odors: Olfaction Elicits Sustained Gazing to Faces and Eyes in 4-Month-Old Infants

This study investigated whether an odor can affect infants' attention to visually presented objects and whether it can selectively direct visual gaze at visual targets as a function of their meaning. Four-month-old infants (n = 48) were exposed to their mother's body odors while their visual exploration was recorded with an eye-movement tracking system. Two groups of infants, who were assigned to either an odor condition or a control condition, looked at a scene composed of still pictures of faces and cars. As expected, infants looked longer at the faces than at the cars but this spontaneous preference for faces was significantly enhanced in presence of the odor. As expected also, when looking at the face, the infants looked longer at the eyes than at any other facial regions, but, again, they looked at the eyes significantly longer in the presence of the odor. Thus, 4-month-old infants are sensitive to the contextual effects of odors while looking at faces. This suggests that early social attention to faces is mediated by visual as well as non-visual cues.

Avian Cerebellar Floccular Fossa Size Is Not a Proxy for Flying Ability in Birds

Extinct animal behavior has often been inferred from qualitative assessments of relative brain region size in fossil endocranial casts. For instance, flight capability in pterosaurs and early birds has been inferred from the relative size of the cerebellar flocculus, which in life protrudes from the lateral surface of the cerebellum. A primary role of the flocculus is to integrate sensory information about head rotation and translation to stabilize visual gaze via the vestibulo-occular reflex (VOR). Because gaze stabilization is a critical aspect of flight, some authors have suggested that the flocculus is enlarged in flying species. Whether this can be further extended to a floccular expansion in highly maneuverable flying species or floccular reduction in flightless species is unknown. Here, we used micro computed-tomography to reconstruct “virtual” endocranial casts of 60 extant bird species, to extract the same level of anatomical information offered by fossils. Volumes of the floccular fossa and entire brain cavity were measured and these values correlated with four indices of flying behavior. Although a weak positive relationship was found between floccular fossa size and brachial index, no significant relationship was found between floccular fossa size and any other flight mode classification. These findings could be the result of the bony endocranium inaccurately reflecting the size of the neural flocculus, but might also reflect the importance of the flocculus for all modes of locomotion in birds. We therefore conclude that the relative size of the flocculus of endocranial casts is an unreliable predictor of locomotor behavior in extinct birds, and probably also pterosaurs and non-avian dinosaurs.

Visual Gaze Behavior of Near-Expert and Expert Fast Pitch Softball Umpires Calling a Pitch

The purpose of this study was to examine the difference in visual gaze behavior between near expert (NE) and expert (E) umpires in a simulated pitch-hit situation in fast pitch softball. An Applied Science Laboratory mobile eye tracker was worn by 4 NE and 4 E fast pitch umpires and recorded their visual gaze behavior while following pitches (internal view). A digital camera located behind the pitcher recorded the external view of the pitcher, hitter, catcher, and umpire actions for each pitch. The internal and external video clips of 10 representative pitches--5 balls and 5 strikes--were synchronized and displayed in a split screen and were then coded for statistical analyses using Quiet eye solution software. Analysis of variance and multivariate analysis of variance statistical analyses of the umpires' gaze behavior during onset, duration, offset, and frequency (fixation/pursuit tracking, saccades, and blinks) were conducted between and within the 5 stages (pitcher's preparation, delivery and release, ball in flight, and umpire call) by umpire's skill level. Significant differences (p < 0.05) observed for combined gaze behavior frequency, type of gaze by phase, quiet eye duration and onset, and ball duration tracking indicated that E umpires' visual control was more stable and economical than NE umpires. Quiet eye significant results indicated that E umpires had an earlier onset (mean = 50.0 ± 13.9% vs. 56 ± 9.5%) and longer duration (mean = 15.1 ± 11.3% vs. 9.3 ± 6.5%) of the pitcher's release area than NE umpires. These findings suggest that gaze behavior of expert fast pitch umpires was more economical, fixated earlier and for a longer period of time on the area where the ball would be released, and was able to track the ball earlier and for a longer period of time.

Scanning Behavior in Echolocating Common Pipistrelle Bats (Pipistrellus pipistrellus)

Echolocating bats construct an auditory world sequentially by analyzing successive pulse-echo pairs. Many other mammals rely upon a visual world, acquired by sequential foveal fixations connected by visual gaze saccades. We investigated the scanning behavior of bats and compared it to visual scanning. We assumed that each pulse-echo pair evaluation corresponds to a foveal fixation and that sonar beam movements between pulses can be seen as acoustic gaze saccades. We used a two-dimensional 16 microphone array to determine the sonar beam direction of succeeding pulses and to characterize the three dimensional scanning behavior in the common pipistrelle bat (Pipistrellus pipistrellus) flying in the field. We also used variations of signal amplitude of single microphone recordings as indicator for scanning behavior in open space. We analyzed 33 flight sequences containing more than 700 echolocation calls to determine bat positions, source levels, and beam aiming. When searching for prey and orienting in space, bats moved their sonar beam in all directions, often alternately back and forth. They also produced sequences with irregular or no scanning movements. When approaching the array, the scanning movements were much smaller and the beam was moved over the array in small steps. Differences in the scanning pattern at various recording sites indicated that the scanning behavior depended on the echolocation task that was being performed. The scanning angles varied over a wide range and were often larger than the maximum angle measurable by our array. We found that echolocating bats use a “saccade and fixate” strategy similar to vision. Through the use of scanning movements, bats are capable of finding and exploring targets in a wide search cone centered along flight direction.

Abstract TP244: Distinguishing Stroke Mimics From Strokes Prior To Treatment With tPA

Introduction: Up to 25% of patients treated with IV tPA are later found to have stroke mimics. Despite low rates of hemorrhagic transformation in these patients, avoiding exposure to unnecessary risk is desirable. Here, we define baseline demographic and clinical characteristics of strokes vs. stroke mimics that might help distinguish these two populations prior to treatment decisions. Methods: All patients treated with IV tPA at our tertiary care academic medical center are registered in a prospectively maintained database. Consecutive patients from 1/09 to 6/12 were entered in this study. Demographic, historical, and neuro exam findings (20 variables) from stroke or stroke mimic patients (based on the discharge diagnosis) were examined. Spearman correlations and binary logistic regression were used to determine variables contributing to mimic status. Post-hoc correlations of individual NIHSS items with mimic status were examined. Results: During this period, 346 patients were treated with IV tPA of which 38 (11%) were stroke mimics. Logistic regression revealed that age (B = -0.61, p &lt; 0.001), history of drug use (B = 1.508, p &lt;0.05), and acute NIHSS facial score (B = -1.12, p &lt; 0.01) significantly predicted mimic status. Sex (B = -1.043, p = .066) and “drip and ship” status (B = 1.04, p = .063) were marginal predictors, whereas history of depression, epilepsy, and number of ED visits in the past 5 years failed to predict mimic status. The logistic regression equation accounted for 39% of the variance in mimic status. Post-hoc Spearman correlations of NIHSS categories with mimic status found that total score ( r = -0.16), visual field loss ( r = -0.16), gaze deviation ( r = -0.21), facial weakness (r = -0.22), dysarthria (r = -0.19), and neglect ( r = -0.18) were all variables significantly associated with acute stroke. Conclusion: Younger age, female gender, history of drug use, and treatment at outlying facility (drip and ship) were associated with stroke mimics. NIHSS categories associated with acute stroke were visual field loss, gaze deviation, facial droop, dysarthria and neglect. Identifying baseline variables that help distinguish mimics may minimize inappropriate treatment with tPA.