Looking (for) patterns: Similarities and differences between infant and adult free scene-viewing patterns.

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 com-mon 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 indi-cate 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 depend-encies between successive fixations and saccades show very similar patterns. A straight-forward conclusion to draw from this set of studies is that infant and adult eye movements are mainly driven by similar underlying basic processes.

Real-world scene perception in infants: What factors guide attention allocation?

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.

Infants' center bias in free viewing of real-world scenes.

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.

Parental negative emotions are related to behavioral and pupillary correlates of infants' attention to facial expressions of emotion.

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.

Gazepath: An eye-tracking analysis tool that accounts for individual differences and data quality.

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.