Synchronous change and perception of object unity: evidence from adults and infants.

Adults and infants display a robust ability to perceive the unity of a center-occluded object when the visible ends of the object undergo common motion (e.g. Kellman, P.J., Spelke, E.S., 1983. Perception of partly occluded objects in infancy. Cognitive Psychology 15, 483-524). Ecologically oriented accounts of this ability focus on the primary of motion in the perception of segregated objects, but Gestalt theory suggests a broader possibility: observers may perceive object unity by detecting patterns of synchronous change, of which common motion is a special case. We investigated this possibility with observations of adults and 4-month-old infants. Participants viewed a center-occluded object whose visible surfaces were either misaligned or aligned, stationary or moving, and unchanging or synchronously changing in color or brightness in various temporal patterns (e.g. flashing). Both alignment and common motion contributed to adults' perception of object unity, but synchronous color changes did not. For infants, motion was an important determinant of object unity, but other synchronous changes and edge alignment were not. When a stationary object with aligned edges underwent synchronous changes in color or brightness, infants showed high levels of attention to the object, but their perception of its unity appeared to be indeterminate. An inherent preference for fast over slow flash rates, and a novelty preference elicited by a change in rate, both indicated that infants detected the synchronous changes, although they failed to use them as information for object unity. These findings favor ecologically oriented accounts of object perception in which surface motion plays a privileged role.     

Development of perceptual completion in infancy

Perceptual completion consists of bridging the gaps imposed by occlusion, such as perceiving the unity of center-occluded objects. It is unknown at present what developmental mechanisms underlie the emergence of functional perceptual completion in infancy. One current debate centers on the role of visible surface motion. According to a core-principles account, perceptual completion emerges simultaneously with the onset of motion discrimination, the sole determinant of unity percepts in infants. According to a contrasting constructivist account, motion discrimination is but one of several independent inputs to perceptual completion. In the present study, 2-month-old infants were tested for both unity perception and motion discrimination in partial-occlusion displays. Motion discrimination obtained under all conditions, even under circumstances in which infants were unable to perceive completion. Four-month-olds showed marked improvements in perceptual completion, most likely because of improvements in information integration. Taken together, these findings support a constructivist view of early perceptual and cognitive development.     

How infants relate looker and object: evidence for a perceptual learning account of gaze following in infancy

In two experiments, it was investigated how preverbal infants perceive the relationship between a person and an object she is looking at. More specifically, it was examined whether infants interpret an adult's object-directed gaze as a marker of an intention to act or whether they relate the person and the object via a mechanism of associative learning. Fourteen-month-old infants observed an adult gazing repeatedly at one of two objects. When the adult reached out to grasp this object in the test trials, infants showed no systematic visual anticipations to it (i.e. first visual anticipatory gaze shifts) but only displayed longer looking times for this object than for another before her hand reached the object. However, they showed visual anticipatory gaze shifts to the correct action target when only the grasping action was presented. The second experiment shows that infants also look longer at the object a person has been gazing at when the person is still present, but is not performing any action during the test trials. Looking preferences for the objects were reversed, however, when the person was absent during the test trials. This study provides evidence for the claim that infants around 1 year of age do not employ other people's object-directed gaze to anticipate future actions, but to establish person-object associations. The implications of this finding for theoretical conceptions of infants' social-cognitive development are discussed.     

Perception of object shape and texture in human newborns: evidence from cross-modal transfer tasks

The present research investigates newborn infants' perceptions of the shape and texture of objects through studies of the bi-directionality of cross-modal transfer between vision and touch. Using an intersensory procedure, four experiments were performed in newborns to study their ability to transfer shape and texture information from vision to touch and from touch to vision. The results showed that cross-modal transfer of shape is not bi-directional at birth. Newborns visually recognized a shape previously held but they failed to tactually recognize a shape previously seen. In contrast, a bi-directional cross-modal transfer of texture was observed. Taken together, the results suggest that newborn infants, like older children and adults, gather information differently in the visual and tactile modes, for different object properties. The findings provide evidence for continuity in the development of mechanisms for perceiving object properties.     

Late influences on perceptual grouping: Amodal completion

Perceptual grouping is generally assumed to be an early visual process that operates on a previously unorganized image-based representation. The present experiment shows that elements perceived as occluded by a closer surface tend to be grouped with elements having the same shape as the amodally completed percept rather than with those having the same retinal shape as the incomplete stimulus. It is therefore concluded that perceptual grouping by shape similarity either occurs after amodal completion or is a temporally extended process that occurs both before and after it.     

Simulating the role of visual selective attention during the development of perceptual completion

We recently proposed a multi‐channel, image‐filtering model for simulating the development of visual selective attention in young infants (Schlesinger, Amso & Johnson, 2007). The model not only captures the performance of 3‐month‐olds on a visual search task, but also implicates two cortical regions that may play a role in the development of visual selective attention. In the current simulation study, we used the same model to simulate 3‐month‐olds’ performance on a second measure, the perceptual unity task. Two parameters in the model – corresponding to areas in the occipital and parietal cortices – were systematically varied while the gaze patterns produced by the model were recorded and subsequently analyzed. Three key findings emerged from the simulation study. First, the model successfully replicated the performance of 3‐month‐olds on the unity perception task. Second, the model also helps to explain the improved performance of 2‐month‐olds when the size of the occluder in the unity perception task is reduced. Third, in contrast to our previous simulation results, variation in only one of the two cortical regions simulated (i.e. recurrent activity in posterior parietal cortex) resulted in a performance pattern that matched 3‐month‐olds. These findings provide additional support for our hypothesis that the development of perceptual completion in early infancy is promoted by progressive improvements in visual selective attention and oculomotor skill.     

Priming effects in picture fragment completion: support for the perceptual closure hypothesis

The perceptual closure hypothesis says that priming will be optimum when just enough information is available in the prime to support closure. Across 5 experiments, a moderately complete fragmented image (Level 4) produced more priming than an almost complete (Level 7) or a very incomplete (Level 1) fragmented image. Only Level 4 priming was improved by increases in prime duration and by showing the prime again after Ss attempted to identify it. Explicit memory played little role in primed fragment completion except for Level 1 priming, in which specific fragment memory was responsible for the entire effect. In contrast, true perceptual learning was shown to be responsible for Level 4 and Level 7 priming. These priming effects cannot be accounted for by the transfer-appropriate procedures approach of Roediger and his colleagues because Level 1 priming produced less transfer to Level 1 identification at test than Level 4 priming did.     

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.     

Learning to perceive object unity: a connectionist account

To explore questions of how human infants begin to perceive partly occluded objects, we devised two connectionist models of perceptual development. The models were endowed with an existing ability to detect several kinds of visual information that have been found important in infants’ and adults’ perception of object unity (motion, co‐motion, common motion, relatability, parallelism, texture and T‐junctions). They were then presented with stimuli consisting of either one or two objects and an occluding screen. The models’ task was to determine whether the object or objects were joined when such a percept was ambiguous, after specified amounts of training with events in which a subset of possible visual information was provided. The model that was trained in an enriched environment achieved superior levels of performance and was able to generalize veridical percepts to a wide range of novel stimuli. Implications for perceptual development in humans, current theories of development and origins of knowledge are discussed.     

An expanded model for perceptual visual single object recognition system using expectation priming following neuroscientific evidence

Under numerous circumstances, humans recognize visual objects in their environment with remarkable response times and accuracy. Existing artificial visual object recognition systems have not yet surpassed human vision, especially in its universality of application. We argue that modeling the recognition process in an exclusive feedforward manner hinders those systems’ performance. To bridge that performance gap between them and human vision, we present a brief review of neuroscientific data, which suggests that considering an agent’s internal influences (from cognitive systems that peripherally interact with visual-perceptual processes) recognition can be improved. Then, we propose a model for visual object recognition which uses these systems’ information, such as affection, for generating expectation to prime the object recognition system, thus reducing its execution times. Later, an implementation of the model is described. Finally, we present and discuss an experiment and its results.     

Infants' haptic perception of object unity in rotating displays

Four-month-old infants were allowed to manipulate, without vision, two rings attached to a bar that permitted each ring to undergo rotary motion against a fixed surface. In different conditions, the relative motions of the rings were rigid, independent, or opposite, and they circled either the same fixed point outside the zone of manipulation or spatially separated points. Infants' perception of the ring assemblies were affected by the nature of the rotary motion in two ways. First, infants perceived a unitary object when the felt ends of the object underwent a common, rigid rotary motion; perception of object unity was stronger in this condition than when the ends underwent either independent or opposite rotary motions. Second, infants perceived two distinct objects when the felt ends of the objects underwent independent rotary motions that centred on distinct fixed points. Perception of the distinctness of the objects was less clear when the ends underwent opposite or independent rotary motions that centred on a common fixed point. These findings provide the first evidence that infants are sensitive to rotary motion patterns and can extrapolate a global pattern of rigid motion from the distinct, local velocities that they produce and experience at their two hands.     

In search of unity: Twardowski,Husserl, and Ingarden on the unity of the object

This paper is devoted to Kazimierz Twardowski's thesis that the unity of a compound object (a whole) can be ensured only by the relations between its parts and the object itself. Twardowski's idea of unity raises many difficulties, especially the threat of petitio principii: the whole is presupposed as furnishing the ground for the unification of its parts, and yet it also seems to be the result of this unification. To avoid these problems, Edmund Husserl sought to refute Twardowski's thesis, and ascribed the role of a principle of unity to the foundational relationships which directly hold between the parts of a whole. Roman Ingarden then seemed to return to Twardowski's concept of unity, but employed it within a different theory of objects, according to which to be an object is to be a subject of properties. I seek to demonstrate that: (1) Twardowski's thesis is sound if a compound object is something over and above its parts; (2) with respect to Husserl's solution, it is not clear as to whether the whole is really something over and above its parts; (3) Ingarden's conception of the subject-properties structure saves Twardowski's thesis; (4) Ingarden's theory of higher-order objects is invalid.     

Motion and edge sensitivity in perception of object unity

Although much evidence indicates that young infants perceive unitary objects by analyzing patterns of motion, infants' abilities to perceive object unity by analyzing Gestalt properties and by integrating distinct views of an object over time are in dispute. To address these controversies, four experiments investigated adults' and infants' perception of the unity of a center-occluded, moving rod with misaligned visible edges. Both alignment information and depth information affected adults' and infants' perception of object unity in similar ways, and infants perceived object unity by integrating information about object features over time. However, infants perceived a moving, misaligned, three-dimensional object as indeterminate in its connectedness, whereas adults perceived it as connected behind the occluder. These findings indicate that the effectiveness of common motion in specifying unified surfaces across an occluder is reduced by misalignment of edges. Alignment information enhances perception of object unity either by serving directly as information for unity or by optimizing the detectability of motion-carried information for unity. In addition, young infants are able to retain information about edge orientation over short intervals in determining connectedness via a process of spatiotemporal integration.     

Early perception-action coupling: eye movements and the development of object perception

We investigated the scanning strategies used by 2- to 3.5-month-old infants when viewing partly occluded object displays. Eye movements were recorded with a corneal reflection system as the infants observed stimuli depicting two rod parts above and below an occluding box. Stimulus parameters were chosen on the basis of past research demonstrating the importance of motion, occluder width, and edge alignment to perception of object unity. Results indicated that the infants tailored scanning to display characteristics, engaging in more extensive scanning when unity perception was challenged by a wide occluder or misaligned edges. In addition, older infants tended to scan the lower parts of the displays more frequently than did younger infants. Exploration of individual differences, however, revealed marked contrasts in specific scanning styles across infants. The findings are consistent with views of perceptual development stressing the importance of information processing skills and self-directed action to the acquisition of object knowledge.     

Pseudoneglect: evidence for both perceptual and attentional factors

When neurologically normal individuals bisect a horizontal line as accurately as possible, they reliably show a slight leftward error. This leftward inaccuracy is called pseudoneglect because errors made by neurologically normal individuals are directionally opposite to those made by persons with visuospatial neglect (Jewell & McCourt, 2000). In the current study, normal right-handed observers bisected horizontal lines that were altered to bias line length judgments either toward the right or the left side of the line. Non-target dots were placed on or near the line stimuli using principles derived from a theory of visual illusions of length called centroid extraction (Morgan, Hole, & Glennerster, 1990). This theory argues that the position of a visual target is calculated as the mean position of all stimuli in close proximity to the target stimulus. We predicted that perceptual alterations that shifted the direction of centroid extraction would also shift the direction of line bisection errors. Our findings confirmed this prediction and support the idea that both perceptual and attentional factors contribute to the pseudoneglect effect.     

Configural processing at birth: evidence for perceptual organisation

We report a series of ten experiments aimed to investigate the newborn's ability to discriminate the components of a visual pattern and to process the visual information that specifies the global configuration of a stimulus. The results reveal that: (i) newborn babies are able to distinguish individual elements of a stimulus (experiments 1A, 1B, 1C, and 1D); (ii) they can group individual elements into a holistic percept on the basis of Gestalt principles (experiments 2A and 3A); (iii) their spontaneous preferences cannot be easily modified by habituation (experiments 2B and 3B); and (iv) when horizontal stimuli are paired with vertical stimuli, they prefer the horizontal ones (experiments 4A and 4B).     

Perception of object unity in chicks: A comparison with the human infant

Newly hatched chicks (Gallus gallus) were imprinted on a display consisting of two rod pieces that moved above and below a central occluder. On test trials, the chicks approached a complete rod in preference to two rod pieces. This finding, supported by those from control coditions, suggests that chicks, soon after hatching, perceive object unity. The results are compared with those from human infants.