We present an exact replication of Experiment 2 from Kovács and Mehler's 2009 study, which showed that 7-month-old infants who are raised bilingually exhibit a cognitive advantage. In the experiment, a sound cue, following an AAB or ABB pattern, predicted the appearance of a visual stimulus on the screen. The stimulus appeared on one side of the screen for nine trials and then switched to the other side. In the original experiment, both mono- and bilingual infants anticipated where the visual stimulus would appear during pre-switch trials. However, during post-switch trials, only bilingual children anticipated that the stimulus would appear on the other side of the screen. The authors took this as evidence of a cognitive advantage. Using the exact same materials in combination with novel analysis techniques (Bayesian analyses, mixed effects modeling and cluster based permutation analyses), we assessed the robustness of these findings in four babylabs (N = 98). Our results did not replicate the original findings: although anticipatory looks increased slightly during post-switch trials for both groups, bilingual infants were not better switchers than monolingual infants. After the original experiment, we presented additional trials to examine whether infants associated sound patterns with cued locations, for which we did not find any evidence either. The results highlight the importance of multicenter replications and more fine-grained statistical analyses to better understand child development. HIGHLIGHTS: We carried out an exact replication across four baby labs of the high-impact study by Kovács and Mehler (2009). We did not replicate the findings of the original study, calling into question the robustness of the claim that bilingual infants have enhanced cognitive abilities. After the original experiment, we presented additional trials to examine whether infants correctly associated sound patterns with cued locations, for which we did not find any evidence. The use of novel analysis techniques (Bayesian analyses, mixed effects modeling and cluster based permutation analyses) allowed us to draw better-informed conclusions.

We conducted a close replication of the seminal work by Marcus and colleagues from 1999, which showed that after a brief auditory exposure phase, 7-month-old infants were able to learn and generalize a rule to novel syllables not previously present in the exposure phase. This work became the foundation for the theoretical framework by which we assume that infants are able to learn abstract representations and generalize linguistic rules. While some extensions on the original work have shown evidence of rule learning, the outcomes are mixed, and an exact replication of Marcus et al.'s study has thus far not been reported. A recent meta-analysis by Rabagliati and colleagues brings to light that the rule-learning effect depends on stimulus type (e.g., meaningfulness, speech vs. nonspeech) and is not as robust as often assumed. In light of the theoretical importance of the issue at stake, it is appropriate and necessary to assess the replicability and robustness of Marcus et al.'s findings. Here we have undertaken a replication across four labs with a large sample of 7-month-old infants (N = 96), using the same exposure patterns (ABA and ABB), methodology (Headturn Preference Paradigm), and original stimuli. As in the original study, we tested the hypothesis that infants are able to learn abstract "algebraic" rules and apply them to novel input. Our results did not replicate the original findings: infants showed no difference in looking time between test patterns consistent or inconsistent with the familiarization pattern they were exposed to.

Describing, analyzing and explaining patterns in eye movement behavior is crucial for understanding visual perception. Further, eye movements are increasingly used in informing cognitive process models. In this article, we start by reviewing basic characteristics and desiderata for models of eye movements. Specifically, we argue that there is a need for models combining spatial and temporal aspects of eye-tracking data (i.e., fixation durations and fixation locations), that formal models derived from concrete theoretical assumptions are needed to inform our empirical research, and custom statistical models are useful for detecting specific empirical phenomena that are to be explained by said theory. In this article, we develop a conceptual model of eye movements, or specifically, fixation durations and fixation locations, and from it derive a formal statistical model --- meeting our goal of crafting a model useful in both the theoretical and empirical research cycle. We demonstrate the use of the model on an example of infant natural scene viewing, to show that the model is able to explain different features of the eye movement data, and to showcase how to identify that the model needs to be adapted if it does not agree with the data. We conclude with discussion of potential future avenues for formal eye movement models.

Determining the meanings of words requires language learners to attend to what other people say. However, it behooves a young language learner to simultaneously encode relevant non-verbal cues, for example, by following the direction of their eye gaze. Sensitivity to cues such as eye gaze might be particularly important for bilingual infants, as they encounter less consistency between words and objects than monolingual infants, and do not always have access to the same word-learning heuristics (e.g., mutual exclusivity). In a preregistered study, we tested the hypothesis that bilingual experience would lead to a more pronounced ability to follow another's gaze. We used a gaze-following paradigm developed by Senju and Csibra (Current Biology, 18, 2008, 668) to test a total of 93 6- to 9-month-old and 229 12- to 15-month-old monolingual and bilingual infants, in 11 laboratories located in 8 countries. Monolingual and bilingual infants showed similar gaze-following abilities, and both groups showed age-related improvements in speed, accuracy, frequency, and duration of fixations to congruent objects. Unexpectedly, bilinguals tended to make more frequent fixations to on-screen objects, whether or not they were cued by the actor. These results suggest that gaze sensitivity is a fundamental aspect of development that is robust to variation in language exposure.

Systematic tendencies such as the center and horizontal bias are known to have a large influence on how and where we move our eyes during static onscreen free scene viewing. However, it is unknown whether these tendencies are learned viewing strategies or are more default tendencies in the way we move our eyes. To gain insight into the origin of these tendencies we explore the systematic tendencies of infants (3 - 20-month-olds, N = 157) and adults (N = 88) in three different scene viewing data sets. We replicated common findings, such as longer fixation durations and shorter saccade amplitudes in infants compared to adults. The leftward bias was never studied in infants, and our results indicate that it is not present, while we did replicate the leftward bias in adults. The general pattern of the results highlights the similarity between infant and adult eye movements. Similar to adults, infants’ fixation durations increase with viewing time and the dependencies between successive fixations and saccades show very similar patterns. A straightforward conclusion to draw from this set of studies is that infant and adult eye movements are mainly driven by similar underlying basic processes.

Circular data are encountered throughout a variety of scientific disciplines, such as in eye movement research as the direction of saccades. Motivated by such applications, mixtures of peaked circular distributions are developed. The peaked distributions are a novel family of Batschelet-type distributions, where the shape of the distribution is warped by means of a transformation function. Because the Inverse Batschelet distribution features an implicit inverse that is not computationally feasible for large or complex data, an alternative called the Power Batschelet distribution is introduced. This distribution is easy to compute and mimics the behavior of the Inverse Batschelet distribution. Inference is performed in both the frequentist framework, through Expectation–Maximization (EM) and the bootstrap, and the Bayesian framework, through MCMC. All parameters can be fixed, which may be done by assumption to reduce the number of parameters. Model comparison can be performed through information criteria or through bridge sampling in the Bayesian framework, which allows performing a wealth of hypothesis tests through the Bayes factor. An R package, flexcircmix, is available to perform these analyses.

Numerous studies have used object familiarity as an independent variable without ever actually defining the construct. Instead, it has been used as a measure of exposure - more exposure of a stimulus making it more familiar. Yet, we argue, that being familiar with an object is more than simple exposure: different levels of experience with and knowledge about an object should be integrated into the construct. Thus, we created the Developmental Object Familiarity Inventory (DOFI) as a new parent report measure to evaluate object familiarity on a six-point scale. The scale points are: (1)My child has never seen this object before, (2)My child has paid attention to this object before, (3)My child has shown interest to explore the object at least once, (4)My child has some knowledge about the object's use, (5)My child can indicate where the object is when asked for it, and (6)My child has and uses a consistent word for the object. This way, real-life familiarity about real-life objects can be measured, as well as, other research questions related to object familiarity (e.g., van Renswoude et al., 2019). Items were 76 objects covering six object categories following the CDI's organization (Fenson et al., 1993): 'vehicles' (9 items), 'toys' (9 items), 'food' (11 items), 'clothing' (14 items), 'household' (18 items), and 'furniture' (15 items) based on the Dutch CDI (N-CDI; Zink & Lejaeger, 2002). In three studies the new measure's reliability and validity was investigated by collecting data about infants between the age of 6 and 24 months. A first study (N = 10 infant reports, M = 15,37; SD = 3,98) shows that the six scale points indeed follow a strict order for all parents for all items. A second study (N = 28 complete infant reports, M = 13,5; SD = 5,5) was aimed at testing the internal structure of the questionnaire (Messick, 1995; Downing, 2003). The survey had great internal consistency (Cronbach's alpha is .991) and a good interitem correlation (d = .63). The scale's ordinality was to be analyzed with a graded response model (GRM, Samejima, 2011; Figure 1). When including age and gender as covariates in the model, age has a significant, positive effect on the latent trait (β = 1.17, t = 2.67, p < .05). Twelve participants responded to the test-retest survey. On average, the interval between measurements was 23 days (min = 9; max = 57; SD = 12,64). With a correlation of r = .86 (p < .001) the test-retest reliability was good. In the third, pilot study, an eye-tracking validation (N = 6 infants between the ages of 7,3 and 22 months, M = 14,4; SD = 4,52), the familiarity scores obtained in the DOFI were attempted to be related to preferential looking. We gathered important information to consider when designing future studies implementing the DOFI (in progress). In conclusion, the DOFI shows great potential to be used in object familiarity related research and might revolutionize the field towards a more natural and generalizable manner of research.

The foci of visual attention were modeled as a function of perceptual salience, adult fixation locations, and attentional control mechanisms (measured in separate tasks) in infants (N = 45, 3- to 15-month-olds) as they viewed static real-world scenes. After controlling for the center bias, the results showed that low-level perceptual salience predicts where infants look. In addition, high-level factors also played a role: Infants fixated parts of the scenes frequently fixated by adults and this effect was stronger for older than younger infants. In line with this finding, infant fixation durations were longer on regions more frequently fixated by adults, implying longer time taken to process the available information. Fixation durations decreased with age, and this decline interacted with orienting skills such that fixation durations decreased faster with age for infants with high orienting skills, relative to infants with low orienting skills. There was a further interaction between fixation durations and selective attention abilities: Infants with low selective attention skills showed a decrease in fixation durations with age, whereas infants with higher selective attention skills showed a slight increase in fixation durations with age. These findings imply that infants' visual processing of static real-world stimuli develops in accord with attentional control.

This study examines how salience and a center bias drive infants' first fixation while looking at complex scenes. Adults are known to have a strong center bias, their first point of gaze is nearly always in the center of the scene. The center bias is likely to be a strategic bias, as looking towards the center minimizes the distance to other parts of the scene and important objects are often located at the center. In an experimental design varying salience regions of scenes and start positions we examined infants' (N = 48, Age = 5-20-month-olds) first fixation after scene onset. The pre-registered hypothesis that infants also have a center bias while looking at real-world scenes was confirmed. The strength of the center bias is correlated with the saliency distribution such that the bias is weaker when the strongest salience is peripheral rather central. In the absence of clear salient regions there still was a strong center bias. These results suggests there is a competition between stimulus-driven factors and a center bias in steering attention from a young age onwards.

Previous evidence revealed links between maternal negative emotions and infants' attention to facial expressions of emotion in clinical and community samples. This study investigated the associations between infants' attention to emotional faces and infants' and parents' negative emotions in a community sample. Infants' (N = 57, Mage = 14.26 months) fixations and pupil responses to fearful, sad, angry versus happy and neutral faces were measured with an eye-tracker. Mothers' and fathers' negative emotions (negative affect, depression, and anxiety), and infants' negative temperament were measured with questionnaires. Infants looked longer at fearful than happy or neutral faces, while they showed less pupil dilation to fearful than to happy or neutral faces. Higher levels of maternal negative emotions were related to less pupillary arousal to emotional facial expressions in infants, while paternal negative emotions did not predict infants' pupil responses. Exploratory analyses suggested a significant link between paternal but not maternal negative emotions and infants' fixations that was moderated by infant negative temperament: Higher levels of negative emotions in fathers were related to longer fixations in children with high levels of negative temperament, while it was related to shorter fixations in infants with low levels of negative temperament. The findings provide support for the idea that exposure to mothers' and fathers' negative emotions play a role on the development of infants' attention to facial expressions in typical development.

Eye-trackers are a popular tool for studying cognitive, emotional, and attentional processes in different populations (e.g., clinical and typically developing) and participants of all ages, ranging from infants to the elderly. This broad range of processes and populations implies that there are many inter- and intra-individual differences that need to be taken into account when analyzing eye-tracking data. Standard parsing algorithms supplied by the eye-tracker manufacturers are typically optimized for adults and do not account for these individual differences. This paper presents gazepath, an easy-to-use R-package that comes with a graphical user interface (GUI) implemented in Shiny (RStudio Inc 2015). The gazepath R-package combines solutions from the adult and infant literature to provide an eye-tracking parsing method that accounts for individual differences and differences in data quality. We illustrate the usefulness of gazepath with three examples of different data sets. The first example shows how gazepath performs on free-viewing data of infants and adults, compared to standard EyeLink parsing. We show that gazepath controls for spurious correlations between fixation durations and data quality in infant data. The second example shows that gazepath performs well in high-quality reading data of adults. The third and last example shows that gazepath can also be used on noisy infant data collected with a Tobii eye-tracker and low (60 Hz) sampling rate.

A robust set of studies show that adults make more horizontal than vertical and oblique saccades, while scanning real-world scenes. In this paper we study the horizontal bias in infants. The directions of eye movements were calculated for 41 infants (M = 8.40 months, SD = 3.74, range = 3.48–15.47) and 47 adults (M = 21.74 years, SD = 4.54, range = 17.89–39.84) while viewing 28 real-world scenes. Saccade directions were binned to study the proportion of saccades in the horizontal, vertical and oblique directions. In addition, saccade directions were also modeled using a mixture of Von Mises distributions, to account for the relatively large amount of variance in infants data. Horizontal bias was replicated in adults and also found in infants, using both the binning and Von Mises approach. Moreover, a developmental pattern was observed in which older infants are more precise in targeting their saccades than younger infants. That infants have a horizontal bias is important in understanding infants’ eye movements. Future studies should account for the horizontal bias in their designs and analyses.

Reproducibility is a defining feature of science, but the extent to which it characterizes current research is unknown. We conducted replications of 100 experimental and correlational studies published in three psychology journals using high-powered designs and original materials when available. Replication effects were half the magnitude of original effects, representing a substantial decline. Ninety-seven percent of original studies had statistically significant results. Thirty-six percent of replications had statistically significant results; 47% of original effect sizes were in the 95% confidence interval of the replication effect size; 39% of effects were subjectively rated to have replicated the original result; and if no bias in original results is assumed, combining original and replication results left 68% with statistically significant effects. Correlational tests suggest that replication success was better predicted by the strength of original evidence than by characteristics of the original and replication teams.