Data collection for the study was conducted in the UCSD Mind, Experience, and Perception Lab (UCSD MEP Lab) at the University of California, San Diego. Funding was provided by NIH R01EY024623 (Bosworth &#38; Dobkins) and NSF SBE-1041725 (Petitto &#38; Allen; subaward to Bosworth). We are grateful to the MEPLab student research team, and to the infants and families in San Diego, California, who participated in this study.

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The authors have nothing to disclose.

We used the preferential looking paradigm to discover evidence that infants may be sensitive to a particular visual cue in the language signal, despite having no prior experience with signed language. Furthermore, this sensitivity was observed only in younger infants, and not older infants, a manifestation of the classic perceptual narrowing function. Evidence of an age-based preference for well-formed syllables based on sonority restrictions allowed us to further hypothesize that sonority may be an important cue for inf...

The paramount goal of developmental science is to study the emergence of cognitive functions, language, and social cognition in infants and children. Eye movements are modulated by participants&#39;&#160;intentions, comprehension, knowledge, interest, and attention to the external world. Collecting oculomotor responses in infants while they orient to and scan visual static or dynamic images can provide information about infants&#39;&#160;emerging understanding of, and attention to, their external visual worlds and the language input they receive.
While eye tracking technology has been around for more than a hundred years, it has only recently advanced in efficiency and usability, permitting it to be used to study infants. In the last decade, eye tracking has revealed much about the mental world of infants. For example, we now know much about short-term memory, object occlusion, and the anticipation of upcoming events in 6-month-olds from gaze behavior1,2,3. Eye tracking can also be used to study infant language learning4. Generally, infant language learning depends on the ability to discriminate sensory cues present in the environment and to identify the cues that are most salient for language transmission5,6. Developmental scientists seek to better understand what these sensory cues are, why they attract infants&#39;&#160;attention, and how attention to these cues scaffold language learning in infants. The present paper presents an eye tracking protocol and a preferential looking paradigm that can be used together to study infants&#39;&#160;sensitivities to such cues in spoken or signed languages.
In Stone, et al.7, eye tracking was used with a preferential looking paradigm to test whether sign-na&#239;ve infants possessed a sensitivity to a set of phonological contrasts in signed language. These contrasts differed by sonority (i.e., perceptual salience), a structural linguistic property present in both spoken and signed languages7,8,9,10,11,12,13. Sonority is thought to be important for phonological restrictions in syllable formation in spoken and signed languages such that syllables which obey sonority-based restrictions are considered to be more &#34;well-formed.&#34;&#160;Infants, when listening to speech, have been observed to show behavioral preferences for well-formed syllables over ill-formed syllables across multiple languages, and even in languages they had never heard before14,15. We hypothesized that infants would also show similar preferences for well-formed syllables in signed language, even if they had no prior experience with signed language.
We further hypothesized that this preference - or sensitivity - would be subject to perceptual narrowing. This is the language acquisition phenomenon where, as the infant approaches its first birthday, the infant&#8217;s early, universal sensitivity to many language features attenuates down to only the features within the language(s) the infant has been exposed to16,17. We recruited younger (six-month-olds) and older (twelve-month-olds) infants, selecting these ages because they are on opposite ends of the perceptual narrowing function for sensitivity to novel phonetic contrasts17,18,19. We predicted that younger infants would demonstrate a preference for well-formed syllables in signed language, but that older infants would not. The infants watched videos consisting of well-formed and ill-formed fingerspelling, selected for two reasons.&#160; First, syllables in fluent fingerspelling are theorized to obey sonority-based phonological restrictions8, providing an opportunity to produce experimental contrasts that directly test whether infants are sensitive to sonority-based cues in early language learning. Second, we chose fingerspelling instead of full signs on the body and face because fingerspelling allowed us to more rigorously control possible perceptual confounds including the speed and size of hand movements, compared to full signs that vary greatly in signing space and movement speed. Our study used videos showing only the hands, but this paradigm is generalizable to videos showing signers and speakers&#39;&#160;heads or full bodies, or even showing animals or inanimate objects, depending on the scientific question and contrasts being studied.
The value using a preferential looking preference paradigm to measure sensitivity to language or sensory contrasts is in its relative simplicity and ease of control. In such paradigms, infants are presented with two stimuli side-by-side which differ by only one dimension or one feature relevant to the research question. Infants are given opportunities to foveate on either stimulus. Total looking times towards each stimulus are recorded and analyzed. A significant difference in looking behavior for the two stimuli indicates that the infant may be capable of perceiving the dimension with which the two stimuli differ. Because both stimuli are shown at the same time and at equal durations, the overall experiment is well-controlled for the idiosyncrasies of infant behavior (inattentiveness, looking elsewhere, fussiness, crying). That is in comparison to other paradigms where stimuli are shown sequentially, in which case, infants may spontaneously show different amounts of attention towards different stimuli for reasons unrelated to the stimuli (e.g., fussier during a period where there were more trials of Stimuli A than Stimuli B). Also, instructions and comprehension of the stimuli are not required; infants merely need to look at it. Last, this paradigm does not require actively monitoring infant behavior for criterion in order to change the stimuli presentation, as is common in infant-controlled habituation paradigms16,20. The looking preference paradigm is also suitable for testing hypotheses about looking preferences rather than differences. In other words, aside from infants being able to discriminate between Stimuli A and Stimuli B, researchers can also test for which stimuli elicited increased or decreased looking behavior, which may be informative about infants&#8217; nascent biases and emerging cognition.
More generally, the advantages of modern, non-invasive eyetracking technology are numerous. Eye tracking relies on measuring near infrared light which is emitted from the device and reflected off the participant&#8217;s eyes1,21. This infrared light is invisible, imperceptible, and completely safe. Eye tracking experiments require no instructions and depends only on passive viewing. Current models generate a copious amount of gaze data in a short amount of time with a simple setup. Infants can sit on their parent&#8217;s lap and, in our experience, they often enjoy the experiment. Most modern remote eye trackers do not require head restraints or items placed on the infant, and are robust to head movements, recovering quickly after blinking, crying, moving out of range, or looking away. If desired, saccade patterns, head position data, and pupillometry can be recorded in addition to eye position data.
The challenges in conducting infant eye tracking research are real, but not insurmountable. Eye tracking data can be noisy due to infants&#39;&#160;movement, inattention, fussiness, and sleepiness. Experiments must be designed so they can be completed in about 10 min or less - which can be an advantage in that lab visits are quick, but also a disadvantage if you need to obtain more data or have several experimental conditions. Another important caveat is that a null finding does not mean that infants are non-sensitive to the experimental manipulation. If infants show no significant difference between Stimuli A and Stimuli B, this finding could mean either (1) an insensitivity to the difference between A and B, or (2) a failure to elicit behavioral preferences. For example, perhaps the infant was equally fascinated by A and B, even though the infant was sensitive to the difference between them. This issue may be addressed by the addition of a second condition, ideally using the same (or highly similar) stimuli but testing along a different dimension for which it is known that infants do exhibit behavioral preferences. If infants do not demonstrate a preference in the first condition, but do so in the second, then it may be interpreted that the infants are capable of demonstrating looking preferences for the stimuli, which can help clarify the interpretation of any null results. Finally, it is vital to precisely calibrate the eye tracker. Calibration must be accurate, with both low spatial and temporal error, so that eye gaze data can be precisely mapped onto the experimental stimuli. In other words, &#34;your study is only as good as your calibration.&#34;&#160;Calibration checks before and after stimuli presentation can provide an added measure of confidence. Detailed and excellent reviews on calibrating eye tracking with infants have been published elsewhere1,21,22,23,24,25,26,27.&#160;

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			<td height="21" style="height:21px;width:223px;">Eye Tracker</td>
			<td style="width:71px;">Tobii</td>
			<td style="width:71px;"></td>
			<td style="width:639px;">Model X120</td>
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			<td height="42" style="height:42px;width:223px;">Experiment Presentation &#38; Gaze Analysis Software</td>
			<td style="width:71px;">Tobii</td>
			<td style="width:71px;"></td>
			<td style="width:639px;">Tobii Studio Pro</td>
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			<td height="22" style="height:23px;width:223px;">Experimenter Monitor</td>
			<td style="width:71px;">Dell</td>
			<td style="width:71px;"></td>
			<td>Dell Professional P2210 22&#34; Wide Monitor</td>
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		<tr height="22">
			<td height="22" style="height:23px;width:223px;">Stimulus Monitor</td>
			<td style="width:71px;">Dell</td>
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			<td>Generic 17&#34; Monitor</td>
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			<td height="42" style="height:42px;width:223px;">CPU</td>
			<td style="width:71px;">Dell</td>
			<td style="width:71px;"></td>
			<td style="width:639px;">Dell Precision T5500 Advanced with 2.13 Ghz Quad Core Intel Xeon Processor and 4 GB DDR3 Memory) with 250 GB SSD hard disk and standard video output cards.</td>
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			<td height="21" style="height:21px;width:223px;">Webcamera</td>
			<td style="width:71px;">Logitech</td>
			<td style="width:71px;"></td>
			<td>Logitech C150 HD Cam</td>
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			<td height="21" style="height:21px;width:223px;">Video Capture Card</td>
			<td style="width:71px;">Osprey</td>
			<td style="width:71px;"></td>
			<td>Osprey 230 Video Capture Card (to capture stimulus that is output to Stimulus Monitor)</td>
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exploring infant sensitivity to visual language using eye tracking and the preferential looking paradigm

We discuss the use of the preferential looking paradigm in eye tracking studies in order to study how infants develop, understand, and attend to the world around them. Eye tracking is a safe and non-invasive way to collect gaze data from infants, and the preferential looking paradigm is simple to design and only requires the infant to be attending to the screen. By simultaneously showing two visual stimuli that differ in one dimension, we can assess whether infants show different looking behavior for either stimulus, thus demonstrating sensitivity to that difference. The challenges in such experimental approaches are that experiments must be kept brief (no more than 10 min) and be carefully controlled such that the two stimuli differ in only one way. The interpretation of null results must also be carefully considered. In this paper, we illustrate a successful example of an infant eye tracking study with a preferential looking paradigm to discover that 6-month-olds are sensitive to linguistic cues in a signed language despite having no prior exposure to signed language, suggesting that infants possess intrinsic or innate sensitivities to these cues.

The sample in Stone, et al.7 consisted of 16 younger infants (mean age = 5.6 &#177; 0.6 months; range = 4.4-6.7 months; 8 female) and 13 older infants (mean age = 11.8 &#177; 0.9 months; range = 10.6-12.8 months; 7 female). None of these infants had seen sign language before. First, we assessed for differences in total looking time between age groups, and found no significant difference (Means: 48.8 s vs. 36.7 s; t(27) = 1.71; p = 0.10). This rules out the possibility of extraneous age-re...

Watch this Scientific Journal Video about Exploring Infant Sensitivity to Visual Language using Eye Tracking and the Preferential Looking Paradigm at JoVE.com

Exploring Infant Sensitivity to Visual Language using Eye Tracking and the Preferential Looking Paradigm

Eye tracking studies using a preferential looking paradigm can be used to study infants&#39;&#160;emerging understanding of, and attention to, their external visual world.

We discuss the use of the preferential looking paradigm in eye tracking studies in order to study how infants develop, understand, and attend to the world ...

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8.2K Views.  Convo Communications. Eye tracking studies using a preferential looking paradigm can be used to study infants' emerging understanding of, and attention to, their external visual world.

Video: Exploring Infant Sensitivity to Visual Language using Eye Tracking and the Preferential Looking Paradigm

A Method to Quantify Visual Information Processing in Children Using Eye Tracking

Visual problems that occur early in life can have major impact on a child's development. Without verbal communication and only based on observational methods, it is difficult to make a quantitative assessment of a child's visual problems. This limits accurate diagnostics in children under the age of 4 years and in children with intellectual disabilities. Here we describe a quantitative method that overcomes these problems. The method uses a remote eye tracker and a four choice preferential looking paradigm to measure eye movement responses to different visual stimuli. The child sits without head support in front of a monitor with integrated infrared cameras. In one of four monitor quadrants a visual stimulus is presented. Each stimulus has a specific visual modality with respect to the background, e.g., form, motion, contrast or color. From the reflexive eye movement responses to these specific visual modalities, output parameters such as reaction times, fixation accuracy and fixation duration are calculated to quantify a child's viewing behavior. With this approach, the quality of visual information processing can be assessed without the use of communication. By comparing results with reference values obtained in typically developing children from 0-12 years, the method provides a characterization of visual information processing in visually impaired children. The quantitative information provided by this method can be advantageous for the field of clinical visual assessment and rehabilitation in multiple ways. The parameter values provide a good basis to: (i) characterize early visual capacities and consequently to enable early interventions; (ii) compare risk groups and follow visual development over time; and (iii), construct an individual visual profile for each child.

A method is described to quantify the quality of visual information processing based on reflexive eye movements in response to specific visual modalities. Reaction times and fixation output parameters are used to characterize visual performance in children with and without visual impairments from 6 months of age.

Visual problems that occur early in life can have major impact on a child's development. Without verbal communication and only based on observational ...

Eye Tracking During Visually Situated Language Comprehension: Flexibility and Limitations in Uncovering Visual Context Effects

The present work is a description and an assessment of a methodology designed to quantify different aspects of the interaction between language processing and the perception of the visual world. The recording of eye-gaze patterns has provided good evidence for the contribution of both the visual context and linguistic/world knowledge to language comprehension. Initial research assessed object-context effects to test&#160;theories of modularity in language processing. In the introduction, we describe how subsequent investigations have taken the role of the wider visual context in language processing as a research topic in its own right, asking questions such as how our visual perception of events and of speakers contributes to&#160;comprehension informed by&#160;comprehenders&#39; experience. Among the examined aspects of the visual context are actions, events, a speaker&#39;s gaze, and emotional facial expressions, as well as spatial object configurations. Following an overview of the eye-tracking method and its different applications, we list the key steps of the methodology in the protocol, illustrating how to successfully use it to study visually-situated language comprehension. A final section presents three sets of representative results and illustrates the benefits and limitations of eye tracking for investigating the interplay between the perception of the visual world and language comprehension.

The present article reviews an eye-tracking methodology for studies on language comprehension. To obtain reliable data, key steps of the protocol must be followed. Among these are the correct set-up of the eye tracker (e.g., ensuring good quality of the eye and head images) and accurate calibration.

The present work is a description and an assessment of a methodology designed to quantify different aspects of the interaction between language processing ...

Using Eye Movements Recorded in the Visual World Paradigm to Explore the Online Processing of Spoken Language

In a typical eye tracking study using the visual world paradigm, participants' eye movements to objects or pictures in the visual workspace are recorded via an eye tracker as the participant produces or comprehends a spoken language describing the concurrent visual world. This paradigm has high versatility, as it can be used in a wide range of populations, including those who cannot read and/or who cannot overtly give their behavioral responses, such as preliterate children, elderly adults, and patients. More importantly, the paradigm is extremely sensitive to fine grained manipulations of the speech signal, and it can be used to study the online processing of most topics in language comprehension at multiple levels, such as the fine grained acoustic phonetic features, the properties of words, and the linguistic structures. The protocol described in this article illustrates how a typical visual world eye tracking study is conducted, with an example showing how the online processing of some semantically complex statements can be explored with the visual world paradigm.

The visual world paradigm monitors participants' eye movements in the visual workspace as they are listening to or speaking a spoken language. This paradigm can be used to investigate the online processing of a wide range of psycholinguistic questions, including semantically complex statements, such as disjunctive statements.

In a typical eye tracking study using the visual world paradigm, participants' eye movements to objects or pictures in the visual workspace are recorded ...

Eye-tracking to Distinguish Comprehension-based and Oculomotor-based Regressive Eye Movements During Reading

Regressive eye movements are eye movements that move backwards through the text and comprise approximately 10-25% of eye movements during reading. As such, understanding the causes and mechanisms of regressions plays an important role in understanding eye movement behavior. Inhibition of return (IOR) is an oculomotor effect that results in increased latency to return attention to a previously attended target versus a target that was not previously attended. Thus, IOR may affect regressions. This paper describes how to design materials to distinguish between regressions caused by comprehension-related and oculomotor processes; the latter is subject to IOR. The method allows researchers to identify IOR and control the causes of regressions. While the method requires tightly controlled materials and large numbers of participants and materials, it allows researchers to distinguish and control the types of regressions that occur in their reading studies.

The method was designed to investigate the role of inhibition of return (IOR) in regressive eye movements during reading. The focus is on differentiating between regressions triggered as a result of comprehension difficulty versus those triggered from oculomotor error, including the role of IOR in the two types of regressions.

Regressive eye movements are eye movements that move backwards through the text and comprise approximately 10-25% of eye movements during reading. As ...

Using the Visual World Paradigm to Study Sentence Comprehension in Mandarin-Speaking Children with Autism

Sentence comprehension relies on the ability to rapidly integrate different types of linguistic and non-linguistic information. However, there is currently a paucity of research exploring how preschool children with autism understand sentences using different types of cues. The mechanisms underlying sentence comprehension remains largely unclear. The present study presents a protocol to examine the sentence comprehension abilities of preschool children with autism. More specifically, a visual world paradigm of eye-tracking is used to explore the moment-to-moment sentence comprehension in the children. The paradigm has multiple advantages. First, it is sensitive to the time course of sentence comprehension and thus can provide rich information about how sentence comprehension unfolds over time. Second, it requires minimal task and communication demands, so it is ideal for testing children with autism. To further minimize the computational burden of children, the present study measures eye movements that arise as automatic responses to linguistic input rather than measuring eye movements that accompany conscious responses to spoken instructions.

We present a protocol to examine the use of morphological cues during real-time sentence comprehension by children with autism.

Sentence comprehension relies on the ability to rapidly integrate different types of linguistic and non-linguistic information. However, there is ...

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.

Gaze in Action: Head-mounted Eye Tracking of Children&#039;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 ...

Investigating the Deployment of Visual Attention Before Accurate and Averaging Saccades via Eye Tracking and Assessment of Visual Sensitivity

This experimental protocol was designed to investigate whether visual attention is obligatorily deployed at the endpoint of saccades. To this end, we recorded the eye position of human participants engaged in a saccade task via eye tracking and assessed visual orientation discrimination performance at various locations during saccade preparation. Importantly, instead of using a single saccade target paradigm for which the saccade endpoint typically coincides roughly with the target, this protocol comprised the presentation of two nearby saccade targets, leading to a distinct spatial dissociation between target locations and saccade endpoint on a substantial number of trials. The paradigm allowed us to compare presaccadic visual discrimination performance at the endpoint of accurate saccades (landing at one of the saccade targets) and of averaging saccades (landing at an intermediate location in between the two targets). We observed a selective enhancement of visual sensitivity at the endpoint of accurate saccades but not at the endpoint of averaging saccades. Rather, before the execution of averaging saccades, visual sensitivity was equally enhanced at both targets, suggesting that saccade averaging follows from unresolved attentional selection among the saccade targets. These results argue against a mandatory coupling between visual attention and saccade programming based on a direct measure of presaccadic visual sensitivity rather than saccadic reaction times, which have been used in other protocols to draw similar conclusions. While our protocol provides a useful framework to investigate the relationship between visual attention and saccadic eye movements at the behavioral level, it can also be combined with electrophysiological measures to extend insights at the neuronal level.

This experimental protocol combined eye tracking and the assessment of presaccadic visual sensitivity in a dual task paradigm, consisting of a free choice saccade task and a visual discrimination task, to investigate the deployment of visual spatial attention before both, accurate and averaging saccades.

This experimental protocol was designed to investigate whether visual attention is obligatorily deployed at the endpoint of saccades. To this end, we ...

Defining the Role Of Language in Infants' Object Categorization with Eye-tracking Paradigms

Assessing infant category learning is a challenging but vital aspect of studying infant cognition. By employing a familiarization-test paradigm, we straightforwardly measure infants&#8217; success in learning a novel category while relying only on their looking behavior. Moreover, the paradigm can directly measure the impact of different auditory signals on the infant categorization across a range of ages. For instance, we assessed how 2-year-olds learn categories in a variety of labeling environments: in our task, 2-year-olds successfully learned categories when all exemplars were labeled&#160;or the first two exemplars were labeled, but they failed to categorize when no exemplars were labeled or only the final two exemplars were labeled. To determine infants&#8217; success in such tasks, researchers can examine both the overall preference displayed by infants in each condition and infants&#8217; pattern of looking over the course of the test phase, using an eye-tracker to provide fine-grained time-course data. Thus, we present a powerful paradigm for identifying the role of language, or any auditory signal, in infants&#8217; object category learning.

Here we present a protocol for familiarization-test paradigms which provide a direct test of infant categorization and help to define the role of language in early category learning.

Assessing infant category learning is a challenging but vital aspect of studying infant cognition. By employing a familiarization-test paradigm, we ...

Experimental Paradigm for Measuring the Effect of Induced Emotion on Grammar Learning

Previous studies have found that emotion has significant influence on the learning of foreign language vocabulary and textual comprehension. However, little attention has been given to the effect of induced emotion on grammar learning. This research examined the influence of positive induced emotion on the learning of Japanese grammatical rules among a group of learners with Chinese as their native language, using a semi-artificial language (i.e. Chipanese), which combines the grammatical rules of Japanese and the vocabulary of Chinese. Music was used to invoke positive emotional conditions in participants. Participants were required to learn Chipanese sentences in a training session through practice and then a grammaticality judgment task was administered to measure learning outcomes. We found that participants in positive emotional states performed less accurately and efficiently than those in the control group. The findings suggest that the protocol is effective in identifying the effect of positive induced emotion on grammar learning. The implications of this experimental paradigm for investigating foreign language learning are discussed.

Here, we present a protocol to measure the effect of positive induced emotion on grammar learning in foreign language learners using a semi-artificial language that integrates the grammatical rules of a foreign language with the lexicon of the learners&#39; native language.

Previous studies have found that emotion has significant influence on the learning of foreign language vocabulary and textual comprehension. However, ...

An Automated Assessment of Visual Acuity in Infants and Toddlers

An Automated Method for Assessing Visual Acuity in Infants and Toddlers Using an Eye-Tracking System

Visual acuity measurement is an important visual function test to perform in infancy and childhood. However, accurate visual acuity measurement in infants is difficult because of deficiencies in their communication ability. This paper presents a novel automated method to assess visual acuity in children (5-36 months old). This method, the automated acuity card procedure (AACP), uses a webcam for eye tracking and recognizes children's watching behaviors automatically. A two-choice preferential-looking test is performed when the tested child watches the visual stimuli shown on a high-resolution digital display screen. When the tested child watches the stimuli, their facial pictures are recorded by the webcam. These pictures are used by the set computer program to analyze their watching behavior. With this procedure, the child's eye movement responses to different stimuli are measured, and their visual acuity is assessed without communication. By comparing the results with grating acuity obtained by Teller Acuity Cards (TACs), AACP performance is deemed comparable to that of TACs.

Author Spotlight: An Automated Method for Assessing Visual Acuity in Infants and Toddlers Using an Eye-Tracking System  

In this paper, we present a novel automated method for assessing visual acuity in infants and toddlers by using an eye-tracking system.

Visual acuity measurement is an important visual function test to perform in infancy and childhood. However, accurate visual acuity measurement in infants ...