Learning and memory facilitate predictive tracking in 4-month-olds

The Influence of Active and Passive Motion Experience on Infants' Visual Prediction Ability

In the present study we examined whether infants' visual prediction abilities were related to different types of motion experiences. We tested 30 6-month-old infants on a visual-spatial prediction task in which they had to visually anticipate the locational reappearance of temporarily occluded moving objects. We assigned infants to one of three experience groups: active locomotion training, passive motion experience, and a no-training control group. We tested the infants' visual prediction abilities before and after these trainings. We found improved infant predictions at a post-training test only for passively trained infants (p = .015, d = -1.033; Bonferroni corrected). Thus, we conclude that infants' visual-spatial predictions of temporally occluded moving objects was facilitated by mere movement experience, even if passive. Visual information gathered during even passive movement seemed sufficient for visual prediction.

The relation between crawling and 9-month-old infants' visual prediction abilities in spatial object processing

We examined whether 9-month-old infants' visual prediction abilities in the context of spatial object processing are related to their crawling ability. A total of 33 9-month-olds were tested; half of them crawled for 7.6weeks on average. A new visual prediction paradigm was developed during which a three-dimensional three-object array was presented in a live setting. During familiarization, the object array rotated back and forth along the vertical axis. While the array was moving, two target objects of it were briefly occluded from view and uncovered again as the array changed its direction of motion. During the test phase, the entire array was rotated around 90° and then rotated back and forth along the horizontal axis. The targets remained at the same position or were moved to a modified placement. We recorded infants' eye movements directed at the dynamically covered and uncovered target locations and analyzed infants' prediction rates. All infants showed higher prediction rates at test and when the targets' placement was modified. Most importantly, the results demonstrated that crawlers had higher prediction rates during test trials as compared with non-crawlers. Our study supports the assumption that crawling experience might enhance 9-month-old infants' ability to correctly predict complex object movement.

Perceptual learning and face processing in infancy

Configural information (spacing between features) contributes to face-processing expertise in adulthood. We examined whether infants can be "trained" to process this information. In Experiment 1, 3.5-month-olds failed to discriminate changes in the spacing between facial features. However, in Experiments 2 and 3, infants processed the same information after being primed with faces in which the spacing was repeatedly altered. Experiment 4 found that priming was not effective with inverted faces or with faces depicting changes in features but not relations among features, indicating that the priming exhibited in Experiments 2 and 3 was specific to upright faces depicting spacing changes. Thus, even young infants who do not readily process facial configural information can be induced to do so through priming. These findings suggest that learning to encode critical structural information contributes to the development of face processing expertise.

Attentional Predictors of 5-month-olds' Performance on a Looking A-not-B Task

In the first year of life, the ability to search for hidden objects is an indicator of object permanence and, when multiple locations are involved, executive function (i.e. inhibition, cognitive flexibility and working memory). The current study was designed to examine attentional predictors of search in 5-month-old infants (as measured by the looking A-not-B task), and whether levels of maternal education moderated the effect of the predictors. Specifically, in a separate task, the infants were shown a unique puppet, and we measured the percentage of time attending to the puppet, as well as the length of the longest look (i.e., peak fixation) directed towards the puppet. Across the entire sample (N =390), the percentage of time attending to the puppet was positively related to performance on the visual A-not-B task. However, for infants whose mothers had not completed college, having a shorter peak looking time (after controlling for percentage of time) was also a predictor of visual A-not-B performance. The role of attention, peak fixation and maternal education in visual search is discussed.

A new system for quantitative evaluation of infant gaze capabilities in a wide visual field

BACKGROUND

The visual assessment of infants poses specific challenges: many techniques that are used on adults are based on the patient's response, and are not suitable for infants. Significant advances in the eye-tracking have made this assessment of infant visual capabilities easier, however, eye-tracking still requires the subject's collaboration, in most cases and thus limiting the application in infant research. Moreover, there is a lack of transferability to clinical practice, and thus it emerges the need for a new tool to measure the paradigms and explore the most common visual competences in a wide visual field. This work presents the design, development and preliminary testing of a new system for measuring infant's gaze in the wide visual field called CareToy C: CareToy for Clinics.

METHODS

The system is based on a commercial eye tracker (SmartEye) with six cameras running at 60 Hz, suitable for measuring an infant's gaze. In order to stimulate the infant visually and audibly, a mechanical structure has been designed to support five speakers and five screens at a specific distance (60 cm) and angle: one in the centre, two on the right-hand side and two on the left (at 30° and 60° respectively). Different tasks have been designed in order to evaluate the system capability to assess the infant's gaze movements during different conditions (such as gap, overlap or audio-visual paradigms). Nine healthy infants aged 4-10 months were assessed as they performed the visual tasks at random.

RESULTS

We developed a system able to measure infant's gaze in a wide visual field covering a total visual range of ±60° from the centre with an intermediate evaluation at ±30°. Moreover, the same system, thanks to different integrated software, was able to provide different visual paradigms (as gap, overlap and audio-visual) assessing and comparing different visual and multisensory sub-competencies. The proposed system endowed the integration of a commercial eye-tracker into a purposive setup in a smart and innovative way.

CONCLUSIONS

The proposed system is suitable for measuring and evaluating infant's gaze capabilities in a wide visual field, in order to provide quantitative data that can enrich the clinical assessment.

Catching moving objects: Differential effects of background motion on action mode selection and movement control in 6- to 10-month-old infants

In human adults the use of visual information for selecting appropriate modes for action appears to be separate from the use of visual information for the control of movements of which the action is composed (Milner & Goodale, [1995] The visual brain in action; [2008] Neuropsychologia 46:774-785). More specifically, action mode selection primarily relies upon allocentric information, whereas movement control mainly exploits egocentric information. In the present study, we investigated to what degree this division is already present in 6- to 10-month-old infants when reaching for moving objects; that is, whether allocentric information is uniquely exploited for action mode selection (i.e., reaching with one or the other hand) or whether it is also used for movement control (i.e., reaching kinematics). Infants were presented with laterally approaching objects at two speeds (i.e., 20 and 40 cm/s) against a stationary or moving background. Background motion affects allocentric information about the object's velocity relative to its background. Results indicated that object speed constrained both infants' action mode selection and movement control. Importantly, however, the influence of background motion was limited to action mode selection and did not extend to movement control. The findings provide further support for the contention that during early development information usage is--at least to some degree--separated for action mode selection and movement control.

Object labeling influences infant phonetic learning and generalization

Different kinds of speech sounds are used to signify possible word forms in every language. For example, lexical stress is used in Spanish (/'be.be/, 'he/she drinks' versus /be.'be/, 'baby'), but not in French (/'be.be/ and /be.'be/ both mean 'baby'). Infants learn many such native language phonetic contrasts in their first year of life, likely using a number of cues from parental speech input. One such cue could be parents' object labeling, which can explicitly highlight relevant contrasts. Here we ask whether phonetic learning from object labeling is abstract-that is, if learning can generalize to new phonetic contexts. We investigate this issue in the prosodic domain, as the abstraction of prosodic cues (like lexical stress) has been shown to be particularly difficult. One group of 10-month-old French-learners was given consistent word labels that contrasted on lexical stress (e.g., Object A was labeled /'ma.bu/, and Object B was labeled /ma.'bu/). Another group of 10-month-olds was given inconsistent word labels (i.e., mixed pairings), and stress discrimination in both groups was measured in a test phase with words made up of new syllables. Infants trained with consistently contrastive labels showed an earlier effect of discrimination compared to infants trained with inconsistent labels. Results indicate that phonetic learning from object labeling can indeed generalize, and suggest one way infants may learn the sound properties of their native language(s).

Development of Three-Dimensional Completion of Complex Objects

Three-dimensional (3D) object completion, the ability to perceive the backs of objects seen from a single viewpoint, emerges at around 6 months of age. Yet, only relatively simple 3D objects have been used in assessing its development. The present study examined infants' 3D object completion when presented with more complex stimuli. Infants (N = 48) were habituated to an "L"-shaped object shown from a limited viewpoint; then they were tested with volumetrically complete (solid) and incomplete (hollow) versions of the object. Four-month-olds and 6-month-old girls had no preference for either display. Six-month-old boys and both sexes at 9.5 months of age showed a novelty preference for the incomplete object. A control group (N = 48), only shown the test displays, had no spontaneous preference. Perceptual completion of complex 3D objects requires infants to integrate multiple, local object features and thus may tax their nascent attentional skills. Infants might use mental rotation to supplement performance, giving an advantage to young boys. Examining the development of perceptual completion of more complex 3D objects reveals distinct mechanisms for the acquisition and refinement of 3D object completion in infancy.

Getting the closer object? An information-based dissociation between vision for perception and vision for movement in early infancy

In human adults two functionally and neuro-anatomically separate systems exist for the use of visual information in perception and the use of visual information to control movements (Milner & Goodale, 1995, 2008). We investigated whether this separation is already functioning in the early stages of the development of reaching. To this end, 6- and 7-month-old infants were presented with two identical objects at identical distances in front of an illusory Ponzo-like background that made them appear to be located at different distances. In two further conditions without the illusory background, the two objects were presented at physically different distances. Preferential reaching outcomes indicated that the allocentric distance information contained in the illusory background affected the perception of object distance. Yet, infants' reaching kinematics were only affected by the objects' physical distance and not by the perceptual distance manipulation. These findings were taken as evidence for the two-visual systems, as proposed by Milner and Goodale (2008), being functional in early infancy. We discuss the wider implications of this early dissociation.

Young infants' perception of the trajectories of two- and three-dimensional objects

We investigated oculomotor anticipations in 4-month-old infants as they viewed center-occluded object trajectories. In two experiments, we examined performance in two-dimensional (2D) and three-dimensional (3D) dynamic occlusion displays and in an additional 3D condition with a smiley face as the moving target stimulus. Rates of anticipatory eye movements were not facilitated by 3D displays or by the (presumably) more salient smiley face relative to the 2D condition. However, latencies of anticipations were reduced, implying that 3D visual information may have supported formation of more robust mental representations of the moving object. Results are interpreted in a context of perceptual constraints on developing cognitive capacities during early infancy.

A Critical Test of Temporal and Spatial Accuracy of the Tobii T60XL Eye Tracker

Infant eye tracking is becoming increasingly popular for its presumed precision relative to traditional looking time paradigms and potential to yield new insights into developmental processes. However, there is strong reason to suspect that the temporal and spatial resolution of popular eye tracking systems is not entirely accurate, potentially compromising any data from an infant eye tracking experiment. Moreover, "best practices" for infant eye tracking, such as knowing which software tool enhances experimental flexibility, remain to be determined. The present investigation was designed to evaluate the temporal and spatial accuracy of data from the Tobii T60XL eye tracker through the use of visual latency and spatial accuracy tasks involving adults and infants. Systematic delays and drifts were revealed in oculomotor response times, and the system's spatial accuracy was observed to deviate somewhat in excess of the manufacturer's estimates; the experimental flexibility of the system appears dependent on the chosen software.

Trajectory recognition as the basis for object individuation: a functional model of object file instantiation and object-token encoding

The perception of persisting visual objects is mediated by transient intermediate representations, object files, that are instantiated in response to some, but not all, visual trajectories. The standard object file concept does not, however, provide a mechanism sufficient to account for all experimental data on visual object persistence, object tracking, and the ability to perceive spatially disconnected stimuli as continuously existing objects. Based on relevant anatomical, functional, and developmental data, a functional model is constructed that bases visual object individuation on the recognition of temporal sequences of apparent center-of-mass positions that are specifically identified as trajectories by dedicated "trajectory recognition networks" downstream of the medial-temporal motion-detection area. This model is shown to account for a wide range of data, and to generate a variety of testable predictions. Individual differences in the recognition, abstraction, and encoding of trajectory information are expected to generate distinct object persistence judgments and object recognition abilities. Dominance of trajectory information over feature information in stored object tokens during early infancy, in particular, is expected to disrupt the ability to re-identify human and other individuals across perceptual episodes, and lead to developmental outcomes with characteristics of autism spectrum disorders.

How does Learning Impact Development in Infancy? The Case of Perceptual Organization

Pattern perception and organization are critical functions of the visual cognition system. Many organizational processes are available early in life, such that infants as young 3 months of age are able to readily utilize a variety of cues to organize visual patterns. However, other processes are not readily evident in young infants, and their development involves perceptual learning. We describe a theoretical framework that addresses perceptual learning in infancy and the manner in which it affects visual organization and development. It identifies five kinds of experiences that induce learning, and suggests that they work via attentional and unitization mechanisms to modify visual organization. In addition, the framework proposes that this kind of learning is abstract, domain general, functional at different ages in a qualitatively similar manner, and has a long-term impact on development through a memory reactivation process. Although most models of development assume that experience is fundamental to development, very little is actually known about the process by which experience affects development. The proposed framework is an attempt to account for this process in the domain of perception.

Anticipatory reaching of seven- to eleven-month-old infants in occlusion situations

The present study examined 7- to 11-month-old infants' anticipatory and reactive reaching for temporarily occluded objects. Infants were presented with laterally approaching objects that moved at different velocities (10, 20, and 40 cm/s) in different occlusion situations (no-, 20 cm-, and 40 cm-occlusion), resulting in occlusion durations ranging between 0 and 4s. Results show that except for object velocity and occlusion distance, occlusion duration was a critical constraint for infants' reaching behaviors. We found that the older infants reached more often, but that an increase in occlusion duration resulted in a decline in reaching frequency that was similar across age groups. Anticipatory reaching declined with increasing occlusion duration, but the adverse effects for longer occlusion durations diminished with age. It is concluded that with increasing age infants are able to retain and use information to guide reaching movements over longer periods of non-visibility, providing support for the graded representation hypothesis (Jonsson & von Hofsten, 2003) and the two-visual systems model (Milner & Goodale, 1995).

How Infants Learn About the Visual World

The visual world of adults consists of objects at various distances, partly occluding one another, substantial and stable across space and time. The visual world of young infants, in contrast, is often fragmented and unstable, consisting not of coherent objects but rather surfaces that move in unpredictable ways. Evidence from computational modeling and from experiments with human infants highlights three kinds of learning that contribute to infants' knowledge of the visual world: learning via association, learning via active assembly, and learning via visual-manual exploration. Infants acquire knowledge by observing objects move in and out of sight, forming associations of these different views. In addition, the infant's own self-produced behavior-oculomotor patterns and manual experience, in particular-are important means by which infants discover and construct their visual world.

Transfer and scaffolding of perceptual grouping occurs across organizing principles in 3- to 7-month-old infants

Previous research has demonstrated that organizational principles become functional over different time courses of development: Lightness similarity is available at 3 months of age, but form similarity is not readily in evidence until 6 months of age. We investigated whether organization would transfer across principles and whether perceptual scaffolding can occur from an already functional principle to a not-yet-operational principle. Six- to 7-month-old infants (Experiment 1) and 3- to 4-month-old infants (Experiment 2) who were familiarized with arrays of elements organized by lightness similarity displayed a subsequent visual preference for a novel organization defined by form similarity. Results with the older infants demonstrate transfer in perceptual grouping: The organization defined by one grouping principle can direct a visual preference for a novel organization defined by a different grouping principle. Findings with the younger infants suggest that learning based on an already functional organizational process enables an organizational process that is not yet functional through perceptual scaffolding.