Name: gaze in action: head-mounted eye tracking of children's dynamic visual attention during naturalistic behavior
Uploaded: 2018-11-14T13:15:00
Description: Watch this Scientific Journal Video about Gaze in Action: Head-mounted Eye Tracking of Children's Dynamic Visual Attention During Naturalistic Behavior at JoVE.com

This research was funded by the National Institutes of Health grants R01HD074601 (C.Y.), T32HD007475-22 (J.I.B., D.H.A.), and F32HD093280 (L.K.S.); National Science Foundation grant BCS1523982 (L.B.S., C.Y.); and by Indiana University through the Emerging Area Research Initiative - Learning: Brains, Machines, and Children (L.B.S.). The authors thank the child and parent volunteers who participated in this research and who agreed to be used in the figures and filming of this protocol. We also appreciate the members of the Computational Cognition and Learning Laboratory, especially Sven Bambach, Anting Chen, Steven Elmlinger, Seth Foster, Grace Lisandrelli, and Charlene Tay, for their assistance in developing and honing this protocol.

This tutorial is based on a procedure for collecting head-mounted eye-tracking data with toddlers approved by the Institutional Review Board at Indiana University. Informed parental consent was obtained prior to toddlers&#39; participation in the experiment.
1. Preparation for the Study
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	<li>Eye-Tracking Equipment. Select one of the several head-mounted eye-tracking systems that are commercially available, either one marketed as specifically for children or modify the s...

<ol>
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This protocol provides guiding principles and practical recommendations for implementing head-mounted eye tracking with infants and young children. This protocol was based on the study of natural toddler behaviors in the context of parent-toddler free play with toys in a laboratory setting. In-house eye-tracking equipment and software were used for calibration and data coding. Nevertheless, this protocol is intended to be generally applicable to researchers using a variety of head-mounted eye-tracking systems to study a ...

The last several decades have seen growing interest in studying the development of infant and toddler visual attention. This interest has stemmed in large part from the use of looking time measurements as a primary means to assess other cognitive functions in infancy and has evolved into the study of infant visual attention in its own right. Contemporary investigations of infant and toddler visual attention primarily measure eye movements during screen-based eye-tracking tasks. Infants sit in a chair or parent&#39;s lap in front of a screen while their eye movements are monitored during the presentation of static images or events. Such tasks, however, fail to capture the dynamic nature of natural visual attention and the means by which children&#39;s natural visual environments are generated - active exploration.
Infants and toddlers are active creatures, moving their hands, heads, eyes, and bodies to explore the objects, people, and spaces around them. Each new development in body morphology, motor skill, and behavior - crawling, walking, picking up objects, engaging with social partners - is accompanied by concomitant changes in the early visual environment. Because what infants do determines what they see, and what they see serves for what they do in visually guided action, studying the natural development of visual attention is best carried out in the context of natural behavior1.
Head-mounted eye trackers (ETs) have been invented and used for adults for decades2,3. Only recently have technological advances made head-mounted eye-tracking technology suitable for infants and toddlers. Participants are outfitted with two lightweight cameras on the head, a scene camera facing outward that captures the first person perspective of the participant and an eye camera facing inward that captures the eye image. A calibration procedure provides training data to an algorithm that maps as accurately as possible the changing positions of the pupil and corneal reflection (CR) in the eye image to the corresponding pixels in the scene image that were being visually attended. The goal of this method is to capture both the natural visual environments of infants and infants&#39; active visual exploration of those environments as infants move freely. Such data can help to answer questions not only about visual attention, but also about a broad range of perceptual, cognitive, and social developments4,5,6,7,8. The use of these techniques has transformed understandings of joint attention7,8,9, sustained attention10, changing visual experiences with age and motor development4,6,11, and the role of visual experiences in word learning12. The present paper provides guiding principles and practical recommendations for carrying out head-mounted eye-tracking experiments with infants and toddlers and illustrates the types of data that can be generated from head-mounted eye tracking in one natural context for toddlers: free-flowing toy play with a parent.

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			<td height="42" style="height:42px;width:216px;">Head-mounted eye tracker</td>
			<td style="width:71px;">Pupil Labs</td>
			<td style="width:352px;">World Camera and Eye Camera</td>
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gaze in action: head-mounted eye tracking of children's dynamic visual attention during naturalistic behavior

Young children's visual environments are dynamic, changing moment-by-moment as children physically and visually explore spaces and objects and interact with people around them. Head-mounted eye tracking offers a unique opportunity to capture children's dynamic egocentric views and how they allocate visual attention within those views. This protocol provides guiding principles and practical recommendations for researchers using head-mounted eye trackers in both laboratory and more naturalistic settings. Head-mounted eye tracking complements other experimental methods by enhancing opportunities for data collection in more ecologically valid contexts through increased portability and freedom of head and body movements compared to screen-based eye tracking. This protocol can also be integrated with other technologies, such as motion tracking and heart-rate monitoring, to provide a high-density multimodal dataset for examining natural behavior, learning, and development than previously possible. This paper illustrates the types of data generated from head-mounted eye tracking in a study designed to investigate visual attention in one natural context for toddlers: free-flowing toy play with a parent. Successful use of this protocol will allow researchers to collect data that can be used to answer questions not only about visual attention, but also about a broad range of other perceptual, cognitive, and social skills and their development.

The method discussed here was applied to a free-flowing toy play context between toddlers and their parents. The study was designed to investigate natural visual attention in a cluttered environment. Dyads were instructed to play freely with a set of 24 toys for six minutes. Toddlers&#39; visual attention was measured by coding the onset and offset of looks to specific regions of interest (ROIs) -- each of the 24 toys and the parent&#39;s face -- and by analyzing the duration and proporti...

Watch this Scientific Journal Video about Gaze in Action: Head-mounted Eye Tracking of Children's Dynamic Visual Attention During Naturalistic Behavior at JoVE.com

Gaze in Action: Head-mounted Eye Tracking of Children's Dynamic Visual Attention During Naturalistic Behavior

Young children do not passively observe the world, but rather actively explore and engage with their environment. This protocol provides guiding principles and practical recommendations for using head-mounted eye trackers to record infants' and toddlers' dynamic visual environments and visual attention in the context of natural behavior.

Young children's visual environments are dynamic, changing moment-by-moment as children physically and visually explore spaces and objects and interact ...

This method can help researchers understand what the world looks like from a young child's perspective, as well as how they allocate their real attention within that view. Compared with screen-based eye tracking, which is widely used in behavioral science, head-mounted eye tracking allows us to monitor where children look during everyday activities like toy play and picture book reading. Demonstrating the procedure will be graduate students Catalina Suarez-Rivera and Yayun Zhang, and lab manager Daniel Pearcy.Before beginning an experiment, modify a system to work with a custom-made infant cap. Select a scene camera that is adjustable in terms of positioning, and has a wide enough angle to capture a field of view appropriate for addressing the research questions of interest. Select an eye camera that is adjustable in terms of positioning, and has an infrared LED positioned in such a way that the cornea of the child's eye will reflect this light.The eye tracking system should be as unobtrusive and lightweight as possible, to provide the greatest chance that young children will tolerate wearing the equipment. Then attach the scene and the eye cameras to a hook and loop strap that is affixed to the opposite side of a piece of hook and loop strap sewn onto a child-sized cap, to embed the system into the cap, and position the cameras so that they will be out of the center of the child's view. For eye-tracking data collection, have two researchers present:one to interact with, and to occupy the child, and one to place and position the eye tracking system.Fully engage the child in an activity that occupies the child's hands, so that the child does not reach up to move or grab the eye-tracking system, and place the eye-tracking system onto the child's head. Position the scene camera low on the forehead to best approximate the child's field of view, and center the scene camera view on what the child will be looking at during the study. To obtain high-quality gaze data, position the eye camera to detect both the pupil and corneal reflection with no cheek or eyelash occlusion throughout the eye's full range of motion.The trickiest part of this protocol is placing the equipment on the child's head and adjusting the cameras without upsetting the child. Speed, confidence, and practice are essential. Once the scene and eye images are as high-quality as can be obtained, draw the child's attention to different locations in their field of view to collect calibration data.Take care that the child's body positioning during the calibration matches the position that will be used during the study. When all the calibration points have been obtained, begin collecting the eye-tracking data. Taking note of any points at which the eye-tracking system gets bumped or misaligned, to allow recalibration as necessary, and to allow separate coding of the data before and after the misalignment.To calibrate the eye-tracking data at the end of the study, open an appropriate calibration software program, and adjust the thresholds of the various detection parameters within the calibration software to obtain a good eye image. During the first round of calibration, identify calibration points at moments when the child is clearly looking to a distinct point in the scene image, keeping in mind that these can be points intentionally created by the researcher during the data collection, or points from within the study, in which the point of gaze is easily identifiable, as long as the pupil is accurately detected for those frames. Create a series of calibration points to establish the mapping between the scene and the eye.If the eye-tracking system changed position at any time during the study, create separate calibrations for the portions before and after the change in position. To code the regions of interest, compile a list of all the regions of interest that should be coded based on the research questions, and use the child's eye image, scene image, and point of gaze track to determine which region of interest is being visually attended. Scroll through frames one by one to watch for moments of the pupil within the eye image as the primary cue that the region of interest may have changed.When a visible movement of the eye occurs, check whether the child was shifting the point of gaze to a new region of interest, or to no defined region of interest. Although the regions of interest are coded separately for each frame, use frames before and after the frame being analyzed to gain contextual information that may aid in determining the correct region of interest. Here, sample region of interest streams for two 18-month old children are shown.Each colored block represents continuous frames during which the child looked at a particular region of interest. Children showed individual differences in their selectivity for different subsets of toys, as evidenced by the differences in proportion of the interactions that each child spent looking at each of the toy regions of interest. Although the total proportion of time both children spent looking at all of the toys was somewhat similar, the proportions of time spent on individual toys varied greatly, both within and between subjects.Moreover, how these proportions of looking time were achieved also differed, with Child Two's mean look duration almost double that of Child One. Another property demonstrated by these data is that both children rarely looked to the faces of their parents during the session, and that when they did, each gaze duration was typically for less than one second. Researchers can place head-mounted eye trackers on children and their social partner simultaneously, as well as integrate this procedure with techniques such as motion-tracking and heart rate monitoring, to provide high-density, multi-modal datasets for answering a variety of questions.The use of these techniques has transformed our understanding of many topics in the developmental literature, including joint and sustained attention, changing visual experiences with age and motor development, and the role of visual experiences in word learning. This protocol has been successfully employed with clinical populations, including children with cochlear implants and children diagnosed with autism spectrum disorders.

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