Discrimination of Possible and Impossible Objects in Infancy

A failure to learn object shape geometry: Implications for convolutional neural networks as plausible models of biological vision

Here we examine the plausibility of deep convolutional neural networks (CNNs) as a theoretical framework for understanding biological vision in the context of image classification. Recent work on object recognition in human vision has shown that both global, and local, shape information is computed, and integrated, early during perceptual processing. Our goal was to compare the similarity in how object shape information is processed by CNNs and human observers. We tested the hypothesis that, unlike the human system, CNNs do not compute representations of global and local object geometry during image classification. To do so, we trained and tested six CNNs (AlexNet, VGG-11, VGG-16, ResNet-18, ResNet-50, GoogLeNet), and human observers, to discriminate geometrically possible and impossible objects. The ability to complete this task requires computation of a representational structure of shape that encodes both global and local object geometry because the detection of impossibility derives from an incongruity between well-formed local feature conjunctions and their integration into a geometrically well-formed 3D global shape. Unlike human observers, none of the tested CNNs could reliably discriminate between possible and impossible objects. Detailed analyses using gradient-weighted class activation mapping (GradCam) of CNN image feature processing showed that network classification performance was not constrained by object geometry. In contrast, if classification could be made based solely on local feature information in line drawings the CNNs were highly accurate. We argue that these findings reflect fundamental differences between CNNs and human vision in terms of underlying image processing structure. Notably, unlike human vision, CNNs do not compute representations of object geometry. The results challenge the plausibility of CNNs as a framework for understanding image classification in biological vision systems.

Increased visual interest and affective responses to impossible figures in early infancy

This research evaluated infants' facial expressions as they viewed pictures of possible and impossible objects on a TV screen. Previous studies in our lab demonstrated that four-month-old infants looked longer at the impossible figures and fixated to a greater extent within the problematic region of the impossible shape, suggesting they were sensitive to novel or unusual object geometry. Our work takes studies of looking time data a step further, determining if increased looking co-occurs with facial expressions associated with increased visual interest and curiosity, or even puzzlement and surprise. We predicted that infants would display more facial expressions consistent with either "interest" or "surprise" when viewing the impossible objects relative to possible ones, which would provide further evidence of increased perceptual processing due to incompatible spatial information. Our results showed that the impossible cubes evoked both longer looking times and more reactive expressions in the majority of infants. Specifically, the data revealed significantly greater frequency of raised eyebrows, widened eyes and returns to looking when viewing impossible figures with the most robust effects occurring after a period of habituation. The pattern of facial expressions were consistent with the "interest" family of facial expressions and appears to reflect infants' ability to perceive systematic differences between matched pairs of possible and impossible objects as well as recognize novel geometry found in impossible objects. Therefore, as young infants are beginning to register perceptual discrepancies in visual displays, their facial expressions may reflect heightened attention and increased information processing associated with identifying irreconcilable contours in line drawings of objects. This work further clarifies the ongoing formation and development of early mental representations of coherent 3D objects.

Three-Dimensional Representations of Objects in Dorsal Cortex are Dissociable from Those in Ventral Cortex

An established conceptualization of visual cortical function is one in which ventral regions mediate object perception while dorsal regions support spatial information processing and visually guided action. This division has been contested by evidence showing that dorsal regions are also engaged in the representation of object shape, even when actions are not required. The critical question is whether these dorsal, object-based representations are dissociable from ventral representations, and whether they play a functional role in object recognition. We examined the neural and behavioral profile of patients with impairments in object recognition following ventral cortex damage. In a functional magnetic resonanace imaging experiment, the blood oxygen level-dependent response in the ventral, but not dorsal, cortex of the patients evinced less sensitivity to object 3D structure compared with that of healthy controls. Consistently, in psychophysics experiments, the patients exhibited significant impairments in object perception, but still revealed residual sensitivity to object-based structural information. Together, these findings suggest that, although in the intact system there is considerable crosstalk between dorsal and ventral cortices, object representations in dorsal cortex can be computed independently from those in ventral cortex. While dorsal representations alone are unable to support normal object perception, they can, nevertheless, support a coarse description of object structural information.

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.

The life-span trajectory of visual perception of 3D objects

Deriving a 3D structural representation of an object from its 2D input is one of the great challenges for the visual system and yet, this type of representation is critical for the successful recognition of and interaction with objects. Perhaps reflecting the importance of this computation, infants have some sensitivity to 3D structural information, and this sensitivity is, at least, partially preserved in the elderly population. To map precisely the life-span trajectory of this key visual computation, in a series of experiments, we compared the performance of observers from ages 4 to 86 years on displays of objects that either obey or violate possible 3D structure. The major findings indicate that the ability to derive fine-grained 3D object representations emerges after a prolonged developmental trajectory and is contingent on the explicit processing of depth information even in late childhood. In contrast, the sensitivity to object 3D structure remains stable even through late adulthood despite the overall reduction in perceptual competence. Together, these results uncover the developmental process of an important perceptual skill, revealing that the initial, coarse sensitivity to 3D information is refined, automatized and retained over the lifespan.

Multisensory object perception in infancy: 4-month-olds perceive a mistuned harmonic as a separate auditory and visual object

Infants learn to use auditory and visual information to organize the sensory world into identifiable objects with particular locations. Here we use a behavioural method to examine infants' use of harmonicity cues to auditory object perception in a multisensory context. Sounds emitted by different objects sum in the air and the auditory system must figure out which parts of the complex waveform belong to different sources (auditory objects). One important cue to this source separation is that complex tones with pitch typically contain a fundamental frequency and harmonics at integer multiples of the fundamental. Consequently, adults hear a mistuned harmonic in a complex sound as a distinct auditory object (Alain, Theunissen, Chevalier, Batty, & Taylor, 2003). Previous work by our group demonstrated that 4-month-old infants are also sensitive to this cue. They behaviourally discriminate a complex tone with a mistuned harmonic from the same complex with in-tune harmonics, and show an object-related event-related potential (ERP) electrophysiological (EEG) response to the stimulus with mistuned harmonics. In the present study we use an audiovisual procedure to investigate whether infants perceive a complex tone with an 8% mistuned harmonic as emanating from two objects, rather than merely detecting the mistuned cue. We paired in-tune and mistuned complex tones with visual displays that contained either one or two bouncing balls. Four-month-old infants showed surprise at the incongruous pairings, looking longer at the display of two balls when paired with the in-tune complex and at the display of one ball when paired with the mistuned harmonic complex. We conclude that infants use harmonicity as a cue for source separation when integrating auditory and visual information in object perception.

Infants' perception of lightness changes related to cast shadows

When humans perceive the lightness of an object’s surface in shadows there is an implicit assumption that cast shadows dim the surface. In two experiments, we investigated whether 5- to 8-month-old infants make this assumption about shadows. According to this shadow assumption, the apparent change in lightness produced by shadows on an object’s surface are attributed to blocked light sources. If infants can use the shadow assumption to perceive the object’s lightness in shadows, they will also be able to detect unnatural lightness changes in shadows. We compared the infants’ looking times to the unnatural and the natural lightness changes in the shadow when an object (duck) goes through the cast shadow. In Experiment 1, we examined whether infants could detect the unnatural lightness changes of the object’s surface in shadows. We created computer-graphic movies of unnatural and natural lightness changes to the duck’s surface. Our results showed that 7- to 8-month-olds but not 5- to 6-month-olds significantly preferred the movie with the unnatural changes in lightness, indicating that only the older infants could detect these changes. In Experiment 2, we confirmed that the infants’ preference was based on the detection of unnatural lightness changes according to the shadow assumption. The natural and the unnatural lightness changes of Experiment 1 were presented without cast shadows. Under these conditions, neither younger nor older infants showed a significant preference. Taken together, the experiments showed that 7- to 8-month-old infants could detect the unnaturalness of a surface’s lightness changes produced by shadows. In conclusion, our findings suggest that 7- to 8-month-old infants can perceive an object’s lightness in shadows by using an assumption that cast shadows dim the surface of an object.

Impossible expectations: fMRI adaptation in the lateral occipital complex (LOC) is modulated by the statistical regularities of 3D structural information

fMRI adaptation (fMRIa), the attenuation of fMRI signal which follows repeated presentation of a stimulus, is a well-documented phenomenon. Yet, the underlying neural mechanisms supporting this effect are not fully understood. Recently, short-term perceptual expectations, induced by specific experimental settings, were shown to play an important modulating role in fMRIa. Here we examined the role of long-term expectations, based on 3D structural statistical regularities, in the modulation of fMRIa. To this end, human participants underwent fMRI scanning while performing a same-different task on pairs of possible (regular, expected) objects and spatially impossible (irregular, unexpected) objects. We hypothesized that given the spatial irregularity of impossible objects in relation to real-world visual experience, the visual system would always generate a prediction which is biased to the possible version of the objects. Consistently, fMRIa effects in the lateral occipital cortex (LOC) were found for possible, but not for impossible objects. Additionally, in alternating trials the order of stimulus presentation modulated LOC activity. That is, reduced activation was observed in trials in which the impossible version of the object served as the prime object (i.e. first object) and was followed by the possible version compared to the reverse order. These results were also supported by the behavioral advantage observed for trials that were primed by possible objects. Together, these findings strongly emphasize the importance of perceptual expectations in object representation and provide novel evidence for the role of real-world statistical regularities in eliciting fMRIa.

Infant Perception of Incongruent Shapes in Cast Shadows

A cast shadow occurs when an object blocks the light from an illumination and projects a dark region onto a surface. Previous studies have reported that adults are slower to identify an object when the object has an incongruent cast shadow than when it has a congruent cast shadow (Castiello, 2001). Here, we used the familiarization-novelty preference procedure to examine whether 5- to 8-month-old infants could detect the relationship between object shapes and cast shadows. In Experiment 1, we examined the infants' ability to detect incongruency between objects and cast shadows. Results showed that 7- to 8-month olds could detect incongruence between the object shapes and the cast shadows, whereas 5- to 6-month olds did not. Yet, our control experiment showed that infants could not detect this incongruence from stimuli in which a white outline had been added to the original cast shadow to decrease the possibility of it being perceived as a cast shadow (Experiment 2). The results of these experiments demonstrate that 7- to 8-month olds responded to the congruence of cast shadows and to consistent contrast polarity between the cast shadow and its background.

Evidence for similar early but not late representation of possible and impossible objects

The perceptual processes that mediate the ability to efficiently represent object 3D structure are still not fully understood. The current study was aimed to shed light on these processes by utilizing spatially possible and impossible objects that could not be created in real 3D space. Despite being perceived as exceptionally unusual, impossible objects still possess fundamental Gestalt attributes and valid local depth cues that may support their initial successful representation. Based on this notion and on recent findings from our lab, we hypothesized that the initial representation of impossible objects would involve common mechanisms to those mediating typical object perception while the perceived differences between possible and impossible objects would emerge later along the processing hierarchy. In Experiment 1, participants preformed same/different classifications of two markers superimposed on a display containing two objects (possible or impossible). Faster reaction times were observed for displays in which the markers were superimposed on the same object (“object-based benefit”). Importantly, this benefit was similar for possible and impossible objects, suggesting that the representations of the two object categories rely on similar perceptual organization processes. Yet, responses for impossible objects were slower compared to possible objects. Experiment 2 was designed to examine the origin of this effect. Participants classified the location of two markers while exposure duration was manipulated. A similar pattern of performance was found for possible and impossible objects for the short exposure duration, with differences in accuracy between these two types of objects emerging only for longer exposure durations. Overall, these findings provide evidence that the representation of object structure relies on a multi-level process and that object impossibility selectively impairs the rendering of fine-detailed description of object structure.

Sensitivity to object impossibility in the human visual cortex: evidence from functional connectivity

Processing spatial configuration is a fundamental requirement for object recognition. Using fMRI, the neural basis underlying this ability was examined while human participants viewed possible and visually similar, but spatially impossible, objects presented for either long or short exposure duration. Response profiles in object-selective cortical regions exhibited sensitivity to object possibility, but only for the long exposure duration. Contrary, functional connectivity, indexed by the pairwise correlations between activation profiles across ROIs, revealed sensitivity to possibility, evident in enhanced correlations for impossible compared with possible objects. Such sensitivity was found even following a brief exposure duration, which allowed only minimal awareness of possibility. Importantly, this sensitivity was correlated with participants' general spatial ability as assessed by an independent neuropsychological test. These results suggest that the visual system is highly susceptible to objects' 3-D structural information even with minimal perceptual awareness. Such sensitivity is captured at the level of functional connectivity between object-selective regions, rather than the absolute level of within-region activity, implicating the role of interregional synchronization in the representation of objects' 3-D structure.

Infants' ability to respond to depth from the retinal size of human faces: comparing monocular and binocular preferential-looking

To examine sensitivity to pictorial depth cues in young infants (4 and 5 months-of-age), we compared monocular and binocular preferential looking to a display on which two faces were equidistantly presented and one was larger than the other, depicting depth from the size of human faces. Because human faces vary little in size, the correlation between retinal size and distance can provide depth information. As a result, adults perceive a larger face as closer than a smaller one. Although binocular information for depth provided information that the faces in our display were equidistant, under monocular viewing, no such information was provided. Rather, the size of the faces indicated that one was closer than the other. Infants are known to look longer at apparently closer objects. Therefore, we hypothesized that infants would look longer at a larger face in the monocular than in the binocular condition if they perceived depth from the size of human faces. Because the displays were identical in the two conditions, any difference in looking-behavior between monocular and binocular viewing indicated sensitivity to depth information. Results showed that 5-month-old infants preferred the larger, apparently closer, face in the monocular condition compared to the binocular condition when static displays were presented. In addition, when presented with a dynamic display, 4-month-old infants showed a stronger 'closer' preference in the monocular condition compared to the binocular condition. This was not the case when the faces were inverted. These results suggest that even 4-month-old infants respond to depth information from a depth cue that may require learning, the size of faces.

Concept formation and categorization of complex, asymmetric, and impossible figures

Impossible figures are striking examples of inconsistencies between global and local perceptual structures, in which the overall spatial configuration of the depicted image does not yield a coherent three-dimensional object. In order to investigate whether structural "impossibility" is an important perceptual property of depicted objects, we used a category formation task in which subjects were asked to divide pictures of shapes into groups that seemed most natural to them. Category formation is usually unidimensional, such that sorting is dominated by a single perceptual property, so this task can serve as a measure of which dimensions are most salient. In Experiment 1, subjects received sets of 12 line drawings consisting of six possible and six impossible objects. Very few subjects grouped the figures by impossibility on the first try, and only half did so after multiple attempts at sorting. In Experiment 2, we investigated other global properties of figures: symmetry and complexity. Subjects readily sorted objects by complexity, but seldom by symmetry. In Experiment 3, subjects were asked to draw each of the figures before sorting them, which had only a minimal effect on categorization. Finally, in Experiment 4, subjects were explicitly instructed to divide the shapes by symmetry or impossibility. Performance on this task was perfect for symmetry, but not for impossibility. Although global properties of figures seem extremely important to our perception, the results suggest that some of these cues are not immediately obvious or salient for most observers.

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.

Measuring young infants' sensitivity to height-in-the-picture-plane by contrasting monocular and binocular preferential-looking

To examine young infants' sensitivity to a pictorial depth cue, we compared monocular and binocular preferential looking to objects of which depth was specified by height-in-the-picture-plane. For adults, this cue generates the perception that a lower object is closer than a higher object. This study showed that 4- and 5-month-old infants fixated the lower, apparently closer, figure more often under the monocular than binocular presentation providing evidence of their sensitivity to the pictorial depth cue. Because the displays were identical in the two conditions except for binocular information for depth, the difference in looking-behavior indicated sensitivity to depth information, excluding a possibility that they responded to 2D characteristics. This study also confirmed the usefulness of the method, preferential looking with a monocular and binocular comparison, to examine sensitivity to a pictorial depth cue in young infants, who are too immature to reach reliably for the closer of two objects.

Oculomotor Exploration of Impossible Figures in Early Infancy

Previous studies with young infants revealed that young infants can distinguish between displays of possible or impossible figures, which may require detection of inconsistent depth relations among local line junctions that disrupt global object configurations. Here, we used an eye-tracking paradigm to record eye movements in young infants during an object discrimination task with matched pairs of possible and impossible figures. Our goal was to identify differential patterns of oculomotor activity as infants viewed pictures of possible and impossible objects. We predicted that infants would actively attend to specific pictorial depth cues that denote shape (e.g., T-junctions), and in the context of an impossible figure that they would fixate to a greater extent in anomalous regions of the display relative to other parts. By the age of 4 months, infants fixated reliably longer overall on displays of impossible vs. possible cubes, specifically within the critical region where the incompatible lines and irreconcilable depth relations were located, implying an early capacity for selective attention to critical line junction information and integration of local depth cues necessary to perceive object coherence.

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.

Infants and adults use line junction information to perceive 3D shape

Two experiments investigated infants' and adults' perception of 3D shape from line junction information. Participants in both experiments viewed a concave wire half-cube frame. In Experiment 1, adults reported that the concave wire frame appeared to be convex when it was viewed monocularly (with one eye covered) and that it appeared to be concave when it was viewed binocularly. In Experiment 2, 5- and 7-month-old infants were shown the concave wire frame under monocular and binocular viewing conditions, and their reaching behavior was recorded. The infants in both age groups reached preferentially toward the center of the wire frame in the monocular condition and toward its edges in the binocular condition. Because infants typically reach to what they perceive to be closest to them, these reaching preferences provide evidence that they perceived the wire frame as convex when they viewed it monocularly and as concave when they viewed it binocularly. These findings suggest that, by 5 months of age, infants, like adults, use line junction information to perceive depth and object shape.

Infants' sensitivity to pictorial depth cues: a review and meta-analysis of looking studies

This paper reviews habituation-dishabituation and preferential-looking studies on the emergence of sensitivity to pictorial depth cues in infancy. This research can be subdivided into two groups. While one group of studies has established responsiveness to pictorial depth cues at 3-5 months of age, the other has found that the ability to extract pictorial 3D information emerges at about 6 months. In the former, young infants were tested for their ability to distinguish between displays that differ in spatial information provided by pictorial depth cues. The results of these studies might demonstrate that 3-5-month-old infants perceive spatial layout from pictorial cues. It is possible, however, that the infants in these studies responded primarily to low-level, two-dimensional stimulus differences. In contrast, the second group of studies controlled for the potential influence of lower-level stimulus features on the infants' experimental performance and more unambiguously demonstrated sensitivity to pictorial depth information in infants 6 months of age and older. In sum, the divergent findings of studies in this area may be resolved by assuming substantial developmental progress in infant sensitivity to pictorial depth cues during the first months of life.

Frontoparietal activation distinguishes face and space from artifact concepts

Empirical and theoretical studies suggest that human knowledge is partly based on innate concepts that are experience-independent. We can, therefore, consider concepts underlying our knowledge as being broadly divided into inherited and acquired ones. Using fMRI, we studied the brain reaction in 20 subjects to violation of face, space (inherited), and artifact (acquired) concepts by presenting them with deformed faces, impossible figures (i.e., impossible chairs), and deformed planes, respectively, as well as their normal counterparts. Violation of the inherited concepts of face and space led to significant activation in frontoparietal cortex, whereas artifacts did not, thus distinguishing neurologically between the two categories. Participants were further exposed to these deformities daily for 1 month to test the supposition that inherited concepts are not modifiable, hence that prolonged exposure would not change the brain circuits that are engaged when viewing them. Consistent with this supposition, our results showed no significant change in activation for both categories, suggesting that such concepts are stable at the neural level at least within a time frame of 1 month. Finally, we investigated the regions of the brain that are critical for object representation. Our results show distinct and overlapping areas in the ventral visual cortex for all three categories, with faces activating the ventral visual cortex inferiorly, especially centered on right fusiform gyrus, and chairs and planes activating more diffuse regions, overlapping with the superior part of face region and mainly located in middle occipital cortex and parietal areas.

Evidence of different developmental trajectories for length estimation according to egocentric and allocentric viewpoints in children and adults

This study investigated the influence of egocentric and allocentric viewpoints on a comparison task of length estimation in children and adults. A total of 100 participants ranging in age from 5 years to adulthood were presented with virtual scenes representing a park landscape with two paths, one straight and one serpentine. Scenes were presented either from an egocentric or allocentric viewpoint. Results showed that when the two paths had the same length, participants always overestimated the length of the straight line for allocentric trials, whereas a development from a systematic overestimation in children to an underestimation of the straight line length in adults was found for egocentric trials. We discuss these findings in terms of the influences of both bias-inhibition processes and school acquisitions.

Die Entwicklung der räumlichen Wahrnehmung im Säuglingsalter: Eine Positionsbestimmung

Zusammenfassung. In den vergangenen Jahrzehnten ist eine Vielzahl experimenteller Studien mit dem Ziel durchgeführt worden, den Zeitpunkt der Entstehung der räumlichen Wahrnehmung im ersten Lebensjahr aufzuspüren. Ein Problem dieser Forschungsarbeiten besteht darin, dass sie auf keine einheitlichen Altersangaben hin konvergieren und so keine sicheren Schlussfolgerungen darüber zulassen, ab wann genau die jeweilige Wahrnehmungsleistung vorhanden ist. Insbesondere im Bereich der bildhaften Tiefenwahrnehmung gibt es eine vermeintliche Diskrepanz in den Ergebnissen von Studien, in denen die Methode des präferentiellen Greifens zur Anwendung kommt, und Studien, in denen das kindliche Blickverhalten beobachtet wird. Aufgabe der Forschung ist daher die Entwicklung und Anwendung von Heuristiken, mit deren Hilfe eine Klärung der Faktoren erfolgen kann, die für derartige unterschiedliche Befundlagen verantwortlich sind. Zu diesen Heuristiken zählen das Verfahren der metaanalytischen Auswertung vorhandener Ergebnisse sowie die Anwendung unterschiedlicher Untersuchungsmethoden und Versuchsdesigns auf einen Inhaltsbereich. Am Beispiel der bildhaften Tiefenwahrnehmung wird dargestellt, dass eine metaanalytische Vorgehensweise die Theorienbildung vorantreiben kann. Zudem werden unterschiedliche experimentelle Designs und Techniken der Datenerhebung skizziert und in ihrer Rolle für die Forschung erläutert.

Spontaneous discrimination of possible and impossible objects by newly hatched chicks

Four-month-old infants can integrate local cues provided by two-dimensional pictures and interpret global inconsistencies in structural information to discriminate between possible and impossible objects. This leaves unanswered the issue of the relative contribution of maturation of biologically predisposed mechanisms and of experience with real objects, to the development of this capability. Here we show that, after exposure to objects in which junctions providing cues to global structure were occluded, day-old chicks selectively approach the two-dimensional image that depicted the possible rather than the impossible version of a three-dimensional object, after restoration of the junctions. Even more impressively, completely naive newly hatched chicks showed spontaneous preferences towards approaching two-dimensional depictions of structurally possible rather than impossible objects. These findings suggest that the vertebrate brain can be biologically predisposed towards approaching a two-dimensional image representing a view of a structurally possible three-dimensional object.

The development of the ability of infants to utilize static cues to create and access representations of object shape

A "transfer-across-depth-cues" method was used to explore the development of the ability to generate and use spatial representations of an object as specified by static pictorial depth cues. Infants were habituated to an object with depth specified by one cue and then presented with the same shape with depth specified by a different cue. Only if an abstract representation of that object had been formed could transfer across cues occur. Shading and line junctions uniquely determined the 3D shapes in these displays so that they appeared to be either a slice of cake with a flat top or a rocket. Without these cues, both line drawings were identical. Infants aged 6 to 7 months showed significant evidence of transfer, while infants aged 4 to 5 months did not. A control experiment demonstrated that the younger infants could discriminate between the objects when a single depth cue specified the shapes. These results are similar to our previous findings, which indicated that 6- to 7-month-old infants show transfer across shading and surface-contour cues, specifying convex and concave surfaces (A. Tsuruhara, T. Sawada, S. Kanazawa, M. K. Yamaguchi, & A. Yonas, 2009). This work supports the hypothesis that the ability to form 3D spatial representations from pictorial depth cues develops at about 6 months of age.

Early biases and developmental changes in self-generated object views

Object recognition depends on the seen views of objects. These views depend in part on the perceivers' own actions as they select and show object views to themselves. The self-selection of object views from manual exploration of objects during infancy and childhood may be particularly informative about the human object recognition system and its development. Here, we report for the first time on the structure of object views generated by 12 to 36 month old children (N = 54) and for comparison adults (N = 17) during manual and visual exploration of objects. Object views were recorded via a tiny video camera placed low on the participant's forehead. The findings indicate two viewing biases that grow rapidly in the first three years: a bias for planar views and for views of objects in an upright position. These biases also strongly characterize adult viewing. We discuss the implications of these findings for a developmentally complete theory of object recognition.

Infant attention, heart rate, and looking time during habituation/dishabituation

Six-month-olds (N=60) were tested in a habituation/dishabituation paradigm during which their heart rate was recorded. In the attention getter condition a salient stimulus appeared prior to each trial. In the no attention getter condition a blank slide appeared. It was hypothesized that the attention getter would lead to a heart rate decrease putting the infant into a state of sustained attention, and facilitate infants' encoding of the habituation stimulus. The encoding hypothesis was strongly supported. Infants in the attention getter condition showed shorter looking times during habituation and correspondingly an increased dishabituation response.

The Relative Contribution of Relative Height, Linear Perspective, and Texture Gradients to Pictorial Depth Perception in 7-Month-Old Infants

In the current preferential-reaching experiments, 7-month-olds were tested for their ability to respond to a combination of relative height and texture gradients. The infants were presented with a display in which these pictorial depth cues specified that two toys were at different distances. The experimental displays differed from the textured surfaces employed in earlier studies in that linear perspective of the contours of the texture elements was omitted. Experiment A shows that the infants still preferred to reach for the apparently nearer toy under monocular, but not binocular, viewing conditions, indicating that they responded to the pictorial depth cues. In experiment B, relative height and texture provided the infants with conflicting information for depth. Here, relative height outperformed texture information. A statistical comparison between the experiments as well as systematic comparisons with experimental conditions from an earlier study (Hemker et al, 2010 Infancy15 6 – 27) revealed that texture gradients, unlike linear perspective, neither enhanced nor weakened the effect exerted by relative height. In sum, 7-month-old infants are obviously more sensitive to relative height and to the linear perspective of the surface contours than to the texture gradients of compression, perspective, and density.

In defense of qualitative changes in development

The balance between the preservation of early cognitive functions and serious transformations on these functions shifts across time. Piaget's writings, which favored transformations, are being replaced by writings that emphasize continuities between select cognitive functions of infants and older children. The claim that young infants possess elements present in the older child's concepts of number, physical impossibility, and object permanence is vulnerable to criticism because the inferences are based primarily on the single measure of change in looking time. It is suggested that investigators use unique constructs to describe phenomena observed in young infants that appear, on the surface, to resemble the psychological competences observed during later developmental stages.

Development of three-dimensional object completion in infancy

Three-dimensional (3D) object completion was investigated by habituating 4- and 6-month-old infants (n= 24 total) with a computer-generated wedge stimulus that pivoted 15 degrees , providing only a limited view. Two displays, rotating 360 degrees , were then shown: a complete, solid volume and an incomplete, hollow form composed only of the sides seen during habituation. There were no reliable preferences for either test display by 4-month-olds. At 6 months, infants showed a reliable novelty preference for the incomplete test display. Infants in a control group (n= 24) not habituated to the limited-view wedge preferred neither test display. By 6 months, infants may represent simple objects as complete in 3D space despite a limited perspective. Possible mechanisms of development of 3D object completion are discussed.

Preference for impossible figures in 4-month-olds

Can infants use interposition and line junction cues to infer three-dimensional (3D) structure? Previous work has shown that in a task that required 4-month-olds to discriminate between static two-dimensional (2D) pictures of possible and impossible cubes, infants exhibited a spontaneous preference for displays of the impossible cube but left open the question of whether they did so on the basis of purely local "critical regions" or whether they were able to employ more global clues. Here infants were presented with possible and impossible cubes in which the strictly local cues that could have derived from exterior binding contours were deleted. Results showed that infants were still able to discriminate possible cubes from impossible cubes, suggesting that longer looking infants are sensitive to global properties and that the capacity to integrate pictorial information to perceive aspects of global 3D shape may develop earlier than demonstrated previously using reaching tasks.

Development of perceptual completion originates in information acquisition

Adults have little difficulty perceiving objects as complete despite occlusion, but newborn infants perceive moving partly occluded objects solely in terms of visible surfaces. The developmental mechanisms leading to perceptual completion have never been adequately explained. Here, the authors examine the potential contributions of oculomotor behavior and motion sensitivity to perceptual completion performance in individual infants. Young infants were presented with a center-occluded rod, moving back and forth against a textured background, to assess perceptual completion. Infants also participated in tasks to assess oculomotor scanning patterns and motion direction discrimination. Individual differences in perceptual completion performance were strongly correlated with scanning patterns but were unrelated to motion direction discrimination. The authors present a new model of development of perceptual completion that posits a critical role for targeted visual scanning, an early developing oculomotor action system.