Name: exploring infant sensitivity to visual language using eye tracking and the preferential looking paradigm
Uploaded: 2019-05-15T15:00:00
Description: Watch this Scientific Journal Video about Exploring Infant Sensitivity to Visual Language using Eye Tracking and the Preferential Looking Paradigm at JoVE.com

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.

The following procedure, which involves human participants, was approved by the Human Research Protections Program at University of California, San Diego.
1. Participant screening and preparation
<ol>
	<li>Recruit infants in the defined age range of interest (e.g., 5 to 14 months old). Use multiple methods, including social media, flyers, postal mail. Consider making agreements with local hospitals or governmental offices to retrieve records listing newborns, their parents, and their mailing...

<ol>
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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>
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			<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>
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			<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>
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			<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>
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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>
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			<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 ...

Eye tracking is ideal for studying how babies learn about the environment around them. And how they might be using those environmental cues to learn language. Here we study those perceptual cues that might be guiding babies language learning.The main advantage of eye tracking and our methods described here is that it is a safe, reliable, and non-invasive way to collect copious amounts of gaze data in a short amount of time. Begin by designing the looking preference paradigm, where two different video stimuli are shown simultaneously, each on one half of the screen. Ensure both stimuli differ by one feature, and are otherwise identical for all other visual elements.Insert attention-grabber images before each trial to maintain and redirect infants'attention to the center of the screen immediately before the trial begins. At the beginning and end end of the experimental sequence, insert a three-point calibration check procedure consisting of three slides, each with one target that appears in the upper left corner, screen center, and lower right corner. Next, position the eye tracker directly under the stimuli monitor, and at a low angle, so that it will face the infant's face as directly head-on as possible.Use rulers and a digital angle gauge to measure the placement, and angle of the eye tracker, and the monitor. Position a separate web camera often called a user, or scene camera above the stimulus monitor to record the participant's full face during the experiment. Finally set up the experimental presentation software, usually commercially available with the eye tracker, to present the stimuli, record the eye movements, record the user or scene camera, display gaze points during the experiment, and optionally perform gaze data analysis.Begin by escorting the parent and infant into the testing room. Explain the procedure, and obtain signed consent to proceed with the experiment. Collect standard demographic and medical information, and information about the infant's language and technology environment.Then, dim the lights in the experimental room, and ensure there are no other obvious visual distractors in the room. Use curtains to occlude the infant's field of view from all distractors in the room. Invite the parent to sit in the chair with the infant sitting on their lap.To provide more stability the parent may strap the infant in a soft booster seat placed on the parent's lap. Use the eye tracker software to confirm that the infant's eyes are visible to the eye tracker. Next, perform a five-point calibration procedure according to the eye tracker instructions.After calibration has been successfully verified, begin the experiment with the three-point calibration check. Manually control the duration of each target, when the infant fixates on the target in one slide, immediately proceed to the next target. Then continue with the experiment, beginning with the attention-grabber before the first trial.Manually control how long the attention-grabber is displayed, and begin the trial when the infant fixates on the attention-grabber. After all trials have been shown, perform the same three-point calibration check procedure again to test for possible signal drift, or calibration changes during the experiment. After the experiment is complete, provide compensation and, if consented to share additional flyers, or materials for the parent to distribute among their peers to assist in the recruitment.Finally, analyze the data by drawing two areas of interest, AOIs, one for each side of the screen. Ensure the AOIs are slightly larger than the visual elements themselves, to accommodate any minor calibration inaccuracies, or standard instrument error. Maintain a gap of about 25 pixels or larger in between the two AOIs in the center of the screen.Then, calculate the total looking times for each AOI for each trial, by summing up all gaze points falling within the AOI, and multiplying this count by the sampling interval. Results indicate that younger infants, but not older infants are sensitive to sonority-based phonological restrictions in sign language, despite having never been exposed to sign language before. Further, younger and older infants have different viewing preferences for upright, and inverted signing stimuli.Specifically, younger infants looked longer at the upright stimuli, while older infants looked longer at the inverted stimuli. Some important things to remember. First, make sure that there are no major changes during recording like in the infant's position.You don't want large body movements, or changes in lighting. Also, it is important that the two stimuli presented to infants differ only in one way, so that if the infants do prefer to look at one of them, then you will know why, and results can be interpreted with respect to that one visual feature. Eye tracking technology allows scientists to better understand about how infants perceive and organize cues in their world.Integrated tracking software, and equipment have become more advanced and versatile, allowing us to test babies more easily and address questions, in ways that we couldn't 10 years ago to better understand infant development.

Research

JoVE Journal

Behavior

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 ...

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 ...

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 ...

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 ...

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 ...

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 ...

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 ...

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 ...

An Experimental Paradigm for Measuring the Effects of Ageing on Sentence Processing

Previous studies have found that older adults have greater difficulties in processing syntactically complex sentences than younger adults. However, the ...

A Methodology for Capturing Joint Visual Attention Using Mobile Eye-Trackers

With the advent of new technological advances, it is possible to study social interactions at a microlevel with unprecedented accuracy. High frequency ...