Validation of an open source, remote web‐based eye‐tracking method (WebGazer) for research in early childhood

Measuring eye movements remotely via the participant's webcam promises to be an attractive methodological addition to in-person eye-tracking in the lab. However, there is a lack of systematic research comparing remote web-based eye-tracking with in-lab eye-tracking in young children. We report a multi-lab study that compared these two measures in an anticipatory looking task with toddlers using WebGazer.js and jsPsych. Results of our remotely tested sample of 18-27-month-old toddlers (N = 125) revealed that web-based eye-tracking successfully captured goal-based action predictions, although the proportion of the goal-directed anticipatory looking was lower compared to the in-lab sample (N = 70). As expected, attrition rate was substantially higher in the web-based (42%) than the in-lab sample (10%). Excluding trials based on visual inspection of the match of time-locked gaze coordinates and the participant's webcam video overlayed on the stimuli was an important preprocessing step to reduce noise in the data. We discuss the use of this remote web-based method in comparison with other current methodological innovations. Our study demonstrates that remote web-based eye-tracking can be a useful tool for testing toddlers, facilitating recruitment of larger and more diverse samples; a caveat to consider is the larger drop-out rate

Quantifying sources of variability in infancy research using the infant-directed-speech preference

Psychological scientists have become increasingly concerned with issues related to methodology and replicability, and infancy researchers in particular face specific challenges related to replicability: For example, high-powered studies are difficult to conduct, testing conditions vary across labs, and different labs have access to different infant populations. Addressing these concerns, we report on a large-scale, multisite study aimed at (a) assessing the overall replicability of a single theoretically important phenomenon and (b) examining methodological, cultural, and developmental moderators. We focus on infants’ preference for infant-directed speech (IDS) over adult-directed speech (ADS). Stimuli of mothers speaking to their infants and to an adult in North American English were created using seminaturalistic laboratory-based audio recordings. Infants’ relative preference for IDS and ADS was assessed across 67 laboratories in North America, Europe, Australia, and Asia using the three common methods for measuring infants’ discrimination (head-turn preference, central fixation, and eye tracking). The overall meta-analytic effect size (Cohen’s d) was 0.35, 95% confidence interval = [0.29, 0.42], which was reliably above zero but smaller than the meta-analytic mean computed from previous literature (0.67). The IDS preference was significantly stronger in older children, in those children for whom the stimuli matched their native language and dialect, and in data from labs using the head-turn preference procedure. Together, these findings replicate the IDS preference but suggest that its magnitude is modulated by development, native-language experience, and testing procedure. (This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 798658.

General and own-species attentional face biases

Humans demonstrate enhanced processing of human faces compared with animal faces, known as own-species bias. This bias is important for identifying people who may cause harm, as well as for recognizing friends and kin. However, growing evidence also indicates a more general face bias. Faces have high evolutionary importance beyond conspecific interactions, as they aid in detecting predators and prey. Few studies have explored the interaction of these biases together. In three experiments, we explored processing of human and animal faces, compared with each other and to nonface objects, which allowed us to examine both own-species and broader face biases. We used a dot-probe paradigm to examine human adults' covert attentional biases for task-irrelevant human faces, animal faces, and objects. We replicated the own-species attentional bias for human faces relative to animal faces. We also found an attentional bias for animal faces relative to objects, consistent with the proposal that faces broadly receive privileged processing. Our findings suggest that humans may be attracted to a broad class of faces. Further, we found that while participants rapidly attended to human faces across all cue display durations, they attended to animal faces only when they had sufficient time to process them. Our findings reveal that the dot-probe paradigm is sensitive for capturing both own-species and more general face biases, and that each has a different attentional signature, possibly reflecting their unique but overlapping evolutionary importance

Look Here! The Development of Attentional Orienting to Symbolic Cues

Although much research has examined the development of orienting to social directional cues (e.g., eye gaze), little is known about the development of orienting to nonsocial directional cues, such as arrows. Arrow cues have been used in numerous studies as a means to study attentional orienting, but the development of children's understanding of such cues has not previously been examined. It remains unclear to what extent the social nature of a cue is important for directing attention; further, it is unknown whether symbolic understanding is necessary for young children to be cued by symbols such as arrows. The present investigation explored when and how arrows cue children's attention. Our results suggest that children younger than 5 years of age orient their attention using the perceptual properties of arrows, and it is not until sometime after 5 years of age that children use the conceptual meaning of arrows to orient their attention. Understanding of the directional meaning of arrows may develop through both exogenous and endogenous orienting; we discuss possible contributions of the compression-based and selection-based learning systems

Finding faces among faces: human faces are located more quickly and accurately than other primate and mammal faces

We tested the specificity of human face search efficiency by examining whether there is a broad window of detection for various face-like stimuli—human and animal faces—or whether own-species faces receive greater attentional allocation. We assessed the strength of the own-species face detection bias by testing whether human faces are located more efficiently than other animal faces, when presented among various other species’ faces, in heterogeneous 16-, 36-, and 64-item arrays. Across all array sizes, we found that, controlling for distractor type, human faces were located faster and more accurately than primate and mammal faces, and that, controlling for target type, searches were faster when distractors were human faces compared to animal faces, revealing more efficient processing of human faces regardless of their role as targets or distractors (Experiment 1). Critically, these effects remained when searches were for specific species’ faces (human, chimpanzee, otter), ruling out a category-level explanation (Experiment 2). Together, these results suggest that human faces may be processed more efficiently than animal faces, both when task-relevant (targets) and task-irrelevant (distractors), even in direct competition with other faces. These results suggest that there is not a broad window of detection for all face-like patterns but that human adults process own-species’ faces more efficiently than other species’ faces. Such own-species search efficiencies may arise through experience with own-species faces throughout development or may be privileged early in development, due to the evolutionary importance of conspecifics’ faces

Superior Detection of Faces in Male Infants at 2 Months

Females generally attend more to social information than males; however, little is known about the early development of these sex differences. With eye tracking, 2-month olds' (N = 101; 44 females) social orienting to faces was measured within four-item image arrays. Infants were more likely to detect human faces compared to objects, suggesting a functional face detection system. Unexpectedly, males looked longer at human faces than females, and only males looked faster and longer at human faces compared to objects. Females, in contrast, looked less at human faces relative to animal faces and objects, appearing socially disinterested. Notably, this is the first report of a male face detection advantage at any age. These findings suggest a unique stage in early infant social development

Face detection in infants and adults: Effects of orientation and color

•Infants and adults detect human faces efficiently, even in visually complex environments.•We observed own-species bias in face detection in 3–5-month-olds, 10–11-moth-olds, and adults.•Infants’ face detection was influenced by low-level manipulations in a species-specific way.•Adults’ face detection was broadly impacted by low-level manipulations equally across species.•Distinct face properties may underlie own-species face processing differences in infants and adults. Humans rapidly locate and recognize human faces, even in complex environments. In the current study, we explored some of the social and perceptual features of faces that may contribute to this ability. We measured infant and adult attention to complex, heterogeneous image arrays containing human and animal faces. Arrays were upright or inverted 180° and in color or grayscale. Infants, aged 3–5 months (n = 51) and 10–11 months (n = 34), viewed 6-item arrays (Experiment 1), whereas adults (n = 120) searched 64-item arrays (Experiment 2). We found that 3- to 5-month-olds already displayed strong own-species biases in face detection—in attention capture, attention holding, and overall detection—suggesting a surprisingly early specialization for human face detection. Furthermore, this remarkable ability was robust, evident even when color and orientation were disrupted, and grew stronger with age. Interestingly, infants’ face detection was reduced by low-level manipulations in a species-specific way, negatively affecting only animal face detection but not affecting human face detection. In contrast, adults’ face detection efficiency was equally reduced by low-level manipulations across species, suggesting potential age differences in own-species face detection. For infants, social relevance (species) may play a more important role than low-level perceptual features, ensuring that infants attend to, connect with, and learn from the people around them. Efficient human face detection during infancy may reflect the uniqueness of own-species faces as a category, perhaps due to their social relevance

Visual Search Efficiency Is Greater for Human Faces Compared to Animal Faces

The Animate Monitoring Hypothesis proposes that humans and animals were the most important categories of visual stimuli for ancestral humans to monitor, as they presented important challenges and opportunities for survival and reproduction; however, it remains unknown whether animal faces are located as efficiently as human faces. We tested this hypothesis by examining whether human, primate, and mammal faces elicit similarly efficient searches, or whether human faces are privileged. In the first three experiments, participants located a target (human, primate, or mammal face) among distractors (non-face objects). We found fixations on human faces were faster and more accurate than primate faces, even when controlling for search category specificity. A final experiment revealed that, even when task-irrelevant, human faces slowed searches for non-faces, suggesting some bottom-up processing may be responsible for the human face search efficiency advantage