Infants’ reasoning about ambiguous motion events: The role of spatiotemporal and dispositional status information

Two experiments investigate whether 7-month-olds reason about the origin of motion events by considering two sources of causally relevant information: spatiotemporal cues and dispositional status information derived from the identification of an object as either animate (with the enduring causal property of self-initiated motion) or inanimate (requiring an external cause of motion). Infants were shown a ball, a human hand, and an animal engaged in a motion event. While dispositional status information remained constant, spatiotemporal relations varied across conditions. Based on looking time data, we conclude that infants attend flexibly to both types of information. Without spatiotemporal cues, infants rely on dispositional status information. When two objects provide dispositional cues to motion origin, but only one also provides corresponding spatiotemporal information, infants attribute the motion to the object providing both types of information. Given an ambiguous motion event with two dispositional motion originators but no additional spatiotemporal cues, infants may prefer either of the two.     

Make the first move: how infants learn about self-propelled objects

In 3 experiments, the author investigated 16- to 20-month-old infants' attention to dynamic and static parts in learning about self-propelled objects. In Experiment 1, infants were habituated to simple noncausal events in which a geometric figure with a single moving part started to move without physical contact from an identical geometric figure that possessed a single static part. Infants were then tested with an event in which the parts of the objects were switched. In Experiments 2 and 3, infants were habituated and tested with identical events except that the part possessed by each object during habitation was switched relative to the first experiment. Results of the experiments revealed that 16-month-olds failed to encode the relation between an object's part and its onset of motion, 18-month-olds were unconstrained in the relations involving self-propulsion that they would encode, and 20-month-olds were constrained in the relations they would encode. The results are discussed with regard to the developmental trajectory of learning about motion properties and the mechanism involved in early concept acquisition.     

Infants' sensitivity to correlations between static and dynamic features in a category context

Four experiments with the habituation procedure investigated 14-22-month-olds' ability to attend to correlations between static and dynamic features embedded in a category context. In Experiment 1, infants were habituated to four objects that exhibited invariant relations between moving features and motion trajectory. Results revealed that 14-month-olds did not process any independent features, 18-month-olds processed individual features but not relations among features, and 22-month-olds processed relations among features. In Experiment 2, 14-month-olds differentiated all of the features in the events in a simpler discrimination task. In Experiments 3a and 3b, 22-month-olds failed to show sensitivity to correlations between dynamic and static features in a category context. In Experiment 4, 22-month-olds, but not 18-month-olds, generalized the learned feature-motion relation to a novel instance. The results are discussed in relation to infants' developing ability to attend to correlations, constraints on learning, category coherence, and the development of the animate-inanimate distinction.     

Can an agent's false belief be corrected by an appropriate communication? Psychological reasoning in 18-month-old infants

Do 18-month-olds understand that an agent's false belief can be corrected by an appropriate, though not an inappropriate, communication? In Experiment 1, infants watched a series of events involving two agents, a ball, and two containers: a box and a cup. To start, agent1 played with the ball and then hid it in the box, while agent2 looked on. Next, in agent1's absence, agent2 moved the ball from the box to the cup. When agent1 returned, agent2 told her "The ball is in the cup!" (informative-intervention condition) or "I like the cup!" (uninformative-intervention condition). During test, agent1 reached for either the box (box event) or the cup (cup event). In the informative-intervention condition, infants who saw the box event looked reliably longer than those who saw the cup event; in the uninformative-intervention condition, the reverse pattern was found. These results suggest that infants expected agent1's false belief about the ball's location to be corrected when she was told "The ball is in the cup!", but not "I like the cup!". In Experiment 2, agent2 simply pointed to the ball's new location, and infants again expected agent1's false belief to be corrected. These and control results provide additional evidence that infants in the second year of life can attribute false beliefs to agents. In addition, the results suggest that by 18 months of age infants expect agents' false beliefs to be corrected by relevant communications involving words or gestures.     

A secret agent? How infants learn about the identity of objects in a causal scene

Four experiments examined the role of correlations between dynamic and static parts on 12- to 16-month-olds' ability to learn the identity of agents and recipients in a simple causal event. Infants were habituated to events in which objects with a dynamic or static part acted as an agent or a recipient and then were tested with an event in which the part-causal role relations were switched. Experiment 1 revealed that 16-month-olds, but not 12-month-olds, associate a dynamic part with the role of agent and a static part with the role of recipient. Experiment 2 showed that 12- and 16-month-olds do not associate a static part with the role of agent or a dynamic part with the role of recipient. Experiment 3 demonstrated that 14-month-olds will learn the relations presented in Experiment 1 and Experiment 2. Experiment 4 revealed that 12-month-olds were able to discriminate the two geometric figures in the events. The results are discussed with respect to infants' developing ability to attend to correlations between dynamic and static cues and the mechanism underlying early object concept acquisition.     

The effect of body and part-based motion on the recognition of unfamiliar objects

We investigated the role of global (body) and local (parts) motion on the recognition of unfamiliar objects. Participants were trained to categorise moving objects and were then tested on their recognition of static images of these targets using a priming paradigm. Each static target shape was primed by a moving object that comprised either the same body and parts motion; same body, different parts motion; different body, same part motion as the learned target or was non-moving. Only the same body but not the same part motion facilitated shape recognition (Experiment 1), even when either motion was diagnostic of object identity (Experiment 2). When parts motion was more related to the object's body motion then it facilitated the recognition of the static target (Experiment 3). Our results suggest that global and local motions are independently accessed during object recognition and have important implications for how objects are represented in memory.     

Sound induces perceptual reorganization of an ambiguous motion display in human infants

Adults who watch an ambiguous visual event consisting of two identical objects moving toward, through, and away from each other and hear a brief sound when the objects overlap report seeing visual bouncing. We conducted three experiments in which we used the habituation/test method to determine whether these illusory effects might emerge early in development. In Experiments 1 and 3 we tested 4‐, 6‐ and 8‐month‐old infants’ discrimination between an ambiguous visual display presented together with a sound synchronized with the objects’ spatial coincidence and the identical visual display presented together with a sound no longer synchronized with coincidence. Consistent with illusory perception, the 6‐ and 8‐month‐old, but not the 4‐month‐old, infants responded to these events as different. In Experiment 2 infants were habituated to the ambiguous visual display together with a sound synchronized with the objects’ coincidence and tested with a physically bouncing object accompanied by the sound at the bounce. Consistent with illusory perception again, infants treated these two events as equivalent by not exhibiting response recovery. The developmental emergence of this intersensory illusion at 6 months of age is hypothesized to reflect developmental changes in object knowledge and attentional mechanisms.     

Object individuation in young infants: Further evidence with an event-monitoring paradigm

Recent results indicate that, when tested with an event-monitoring task, 7.5- and 9.5-month-olds give evidence that they can individuate objects in different-objects occlusion events – events in which two distinct objects appear successively on either side of an occluder (Wilcox and Baillargeon, in press). The present research sought to confirm and extend these findings. The experiments examined 7.5- and 4.5-month-olds’ ability to correctly interpret a different-objects (ball-box condition) and a same-object (ball-ball condition) occlusion event. The infants in the ball-box condition saw a test event in which a ball disappeared behind the left edge of a screen; after a pause, a box emerged from behind the screen's right edge. For half of the infants (wide-screen event), the screen was wide and could occlude the ball and box simultaneously; for the other infants (narrow-screen event), the screen was narrow and should not have been able to occlude the ball and box at the same time. The infants in the ball-ball condition saw identical wide- and narrow-screen events except that the ball appeared on both sides of the screen. The infants in the ball-box condition looked reliably longer at the narrow- than at the wide-screen event, whereas those in the ball-ball condition tended to look equally at the events. These results suggest that the ball-box infants (a) were led by the featural differences between the ball and box to view them as distinct objects; (b) judged that the ball and box could both be occluded by the wide but not the narrow screen; and (c) were surprised in the narrow-screen event when this judgment was violated. In contrast, the ball-ball infants (a) assumed, based on the featural similarities of the balls that appeared on either side of the screen, that they were one and the same ball, and (b) realized that the ball could be occluded by either the wide or the narrow screen. These results indicate that, by 4.5 months of age, infants are able to use featural information to correctly interpret different-objects and same-object occlusion events. These findings are discussed in the context of the newly-drawn distinction between event-monitoring and event-mapping paradigms (Wilcox and Baillargeon, in press).     

Six-month-olds’ ability to use linguistic cues when interpreting others’ pointing actions

The present research investigated whether six-month-olds who rarely produce pointing actions can detect the object-directedness and communicative function of others’ pointing actions when linguistic information is provided. In Experiment 1, infants were randomly assigned to either a novel-word or emotional-vocalization condition. They were first familiarized with an event in which an actor uttered either a novel label (novel-word condition) or exclamatory expression (emotional-vocalization condition) and then pointed to one of two objects. Next, the positions of the objects were switched. During test trials, each infant watched the new-referent event where the actor pointed to the object to which the actor had not pointed before or the old-referent event where the actor pointed to the old object in its new location. Infants in the novel-word condition looked reliably longer at the new-referent event than at the old-referent event, suggesting that they encoded the object-directedness of the actor’s point. In contrast, infants in the emotional-vocalization condition showed roughly equal looking times to the two events. To further examine infants’ understanding of the communicative aspect of an actor’s point using a different communicative context, Experiment 2 used an identical procedure to the novel-word condition in Experiment 1, except there was only one object present during the familiarization trials. When the familiarization trials did not include a contrasting object, we found that the communicative intention of the actor’s point could be ambiguous. The infants showed roughly equal looking times during the two test events. The current research suggests that six-month-olds understand the object-directedness and communicative intention of others’ pointing when presented with a label, but not when presented with an emotional non-speech vocalization.     

Knowing who dunnit: Infants identify the causal agent in an unseen causal interaction

Preverbal infants can represent the causal structure of events, including distinguishing the agentive and receptive roles and categorizing entities according to stable causal dispositions. This study investigated how infants combine these 2 kinds of causal inference. In Experiments 1 and 2, 9.5-month-olds used the position of a human hand or a novel puppet (causal agents), but not a toy train (an inert object), to predict the subsequent motion of a beanbag. Conversely, in Experiment 3, 10- and 7-month-olds used the motion of the beanbag to infer the position of a hand but not of a toy block. These data suggest that preverbal infants expect a causal agent as the source of motion of an inert object.     

Infants' sensitivity to effects of gravity on visible object motion.

A preference method probed infants' perception of object motion on an inclined plane. Infants viewed videotaped events in which a ball rolled downward (or upward) while speeding up (or slowing down). Then infants were tested with events in which the ball moved in the opposite direction with appropriate or inappropriate acceleration. Infants aged 7 months, but not 5 months, looked longer at the test event with inappropriate acceleration, suggesting emerging sensitivity to gravity. A further study tested whether infants appreciate that a stationary object released on an incline moves downward rather than upward; findings again were positive at 7 months and negative at 5 months. A final study provided evidence, nevertheless, that 5-month-old infants discriminate downward from upward motion and relate downward motion in videotaped events to downward motion in live events. Sensitivity to certain effects of gravity appears to develop in infancy.     

Color-function categories that prime infants to use color information in an object individuation task

There is evidence for developmental hierarchies in the type of information to which infants attend when reasoning about objects. Investigators have questioned the origin of these hierarchies and how infants come to identify new sources of information when reasoning about objects. The goal of the present experiments was to shed light on this debate by identifying conditions under which infants’ sensitivity to color information, which is slow to emerge, could be enhanced in an object individuation task. The outcome of Experiment 1 confirmed and extended previous reports that 9.5-month-olds can be primed, through exposure to events in which the color of an object predicts its function, to attend to color differences in a subsequent individuation task. The outcomes of Experiments 2-4 revealed age-related changes in the nature of the representations that support color priming. This is exemplified by three main findings. First, the representations that are formed during the color-function events are relatively specific. That is, infants are primed to use the color difference seen in the color-function events to individuate objects in the test events, but not other color differences. Second, 9.5-month-olds can be led to form more abstract event representations, and then generalize to other colors in the test events if they are shown multiple pairs of colors in the color-function events. Third, slightly younger 9-month-olds also can be led to form more inclusive categories with multiple color pairs, but only when they are allowed to directly compare the exemplars in each color pair during the present events. These results shed light on the development of categorization abilities, cognitive mechanisms that support color-function priming, and the kinds of experiences that can increase infants’ sensitivity to color information.     

How do 8‐month‐old infants recognize causality in object motion and that in human action?1

Abstract: In Experiment 1, 8‐month‐old infants were first habituated to the event in which a moving object collided with another behind an occluder, then they were shown the two test events with no occluder: the contact event, in which the two objects actually collided, and the non‐contact event, in which the second object started to move without contact with the first. The infants looked at both events for an equal amount of time. In Experiment 2, in which the first object was a human actor, however, infants looked at the non‐contact event reliably longer than the contact event. In Experiment 3, in which both objects were human actors stood face‐to‐back, infants looked at the non‐contact event longer, whereas in Experiment 4, in which human actors faced toward each other, infants looked at both events equally. In Experiment 5, in which the first actor told the second to go, 10‐month‐old infants looked at both events for an equal amount of time. These results suggest that 8‐ and 10‐month‐old infants appreciate different causal principles between objects and humans, and that, in doing this, they may acknowledge the possibility of communication between humans.     

Priming 4.5-month-old infants to use height information by enhancing retrieval

How do infants select and use information that is relevant to the task at hand? Infants treat events that involve different spatial relations as distinct, and their selection and use of object information depends on the type of event they encounter. For example, 4.5-month-olds consider information about object height in occlusion events, but infants typically fail to do so in containment events until they reach the age of 7.5 months. However, after seeing a prime involving occlusion, 4.5-month-olds became sensitive to height information in a containment event (Experiment 1). The enhancement lasted over a brief delay (Experiment 2) and persisted even longer when infants were shown an additional occlusion prime but not an object prime (Experiment 3). Together, these findings reveal remarkable flexibility in visual representations of young infants and show that their use of information can be facilitated not by strengthening object representations per se but by strengthening their tendency to retrieve available information in the representations.     

Eye tracking provides no evidence that young infants understand path obstruction

In two experiments with 47 4-month-olds, we investigated attention to key aspects of events in which an object moved along a partly occluded path that contained an obstruction. Infants were familiarized with a ball rolling behind an occluder to be revealed resting on an end wall, and on test trials an obstruction wall was placed in the ball's path. In Experiment 1, we did not find longer looking when the object appeared in an impossible location beyond the obstruction, and infants did not selectively fixate the object in this location. In Experiment 2, after rolling one or two balls, we measured infants' fixations of a two-object outcome with one ball in a novel but possible resting position and the other in a familiar but impossible location beyond the obstruction. Infants looked longer at the ball in the possible but novel location, likely reflecting a looking preference for location novelty. Thus we obtained no evidence that infants reasoned about obstruction and identified a violation on that basis.     

Perception of Mooney faces by young infants: the role of local feature visibility, contrast polarity, and motion

We examined the ability of young infants (3- and 4-month-olds) to detect faces in the two-tone images often referred to as Mooney faces. In Experiment 1, this performance was examined in conditions of high and low visibility of local features and with either the presence or absence of the outer head contour. We found that regardless of the presence of the outer head contour, infants preferred upright over inverted two-tone face images only when local features were highly visible (Experiment 1a). We showed that this upright preference disappeared when the contrast polarity of two-tone images was reversed (Experiment 1b), reflecting operation of face-specific mechanisms. In Experiment 2, we investigated whether motion affects infants' perception of faces in Mooney faces. We found that when the faces appeared to be rigidly moving, infants did show an upright preference in conditions of low visibility of local features (Experiment 2a). Again the preference disappeared when the contrast polarity of the image was reversed (Experiment 2b). Together, these results suggest that young infants have the ability to integrate fragmented image features to perceive faces from two-tone face images, especially if they are moving. This suggests that an interaction between motion and form rather than a purely motion-based process (e.g., structure from motion) facilitates infants' perception of faces in ambiguous two-tone images.     

Infant perception of causal motion produced by humans and inanimate objects

Both the movements of people and inanimate objects are intimately bound up with physical causality. Furthermore, in contrast to object movements, causal relationships between limb movements controlled by humans and their body displacements uniquely reflect agency and goal-directed actions in support of social causality. To investigate the development of sensitivity to causal movements, we examined the looking behavior of infants between 9 and 18 months of age when viewing movements of humans and objects. We also investigated whether individual differences in gender and gross motor functions may impact the development of the visual preferences for causal movements. In Experiment 1, infants were presented with walking stimuli showing either normal body translation or a “moonwalk” that reversed the horizontal motion of body translations. In Experiment 2, infants were presented with unperformable actions beyond infants’ gross motor functions (i.e., long jump) either with or without ecologically valid body displacement. In Experiment 3, infants were presented with rolling movements of inanimate objects that either complied with or violated physical causality. We found that female infants showed longer looking times to normal walking stimuli than to moonwalk stimuli, but did not differ in their looking time to movements of inanimate objects and unperformable actions. In contrast, male infants did not show sensitivity to causal movement for either category. Additionally, female infants looked longer at social stimuli of human actions than male infants. Under the tested circumstances, our findings indicate that female infants have developed a sensitivity to causal consistency between limb movements and body translations of biological motion, only for actions with previous visual and motor exposures, and demonstrate a preference toward social information.     

Development of manipulatory skills and the deployment of attention

Two independent tasks, object manipulation and auditory-visual matching, were used to examine the relationship between developing manual action skills and attention to intermodal object properties in 3.5- and 5.5-month-olds. Although handling skills improved with age, with older infants demonstrating more varied manipulation, there were no age differences for the matching task. When grouped by handling skills, a significant interaction between skill and event type was found for the two age groups combined and for 5.5-month-olds alone. Auditory-visual matching of social events did not vary with handling skills, whereas auditory-visualmatching of object events did. Infants at higher skill levels responded similarly to social and object events, whereas less skilled infants' matching preferences were weaker for object events. These findings indicate that infants increase their attention to auditory and visual properties of objects as this information becomes useful for guiding new actions. This effect is independent of age due to considerable individual variability in the development of object handling skills.     

Object manipulation facilitates kind-based object individuation of shape-similar objects

Five experiments investigated the importance of shape and object manipulation when 12-month-olds were given the task of individuating objects representing exemplars of kinds in an event-mapping design. In Experiments 1 and 2, results of the study from Xu, Carey, and Quint (2004, Experiment 4) were partially replicated, showing that infants were able to individuate two natural-looking exemplars from different categories, but not two exemplars from the same category. In Experiment 3, infants failed to individuate two shape-similar exemplars (from Pauen, 2002a) from different categories. However, Experiment 4 revealed that allowing infants to manipulate objects shortly before the individuation task enabled them to individuate shape-similar objects from different categories. In Experiment 5, allowing object manipulation did not induce infants to individuate natural-looking objects from the same category. These findings suggest that object manipulation facilitates kind-based individuation of shape-similar objects by 12-month-olds.     

When do infants understand that they can obtain a desired part of a composite object by grasping another part?

When do infants start to understand that they can grasp an object by its handle when the interesting part is out of reach? Whereas it is known from preferential looking tasks that already at three months of age infants show surprise when all parts of an object do not move together, little is known about when infants are able to use such knowledge in an active grasp situation. To answer this question we presented six, eight, and 10 month-old infants in a cross-sectional and a longitudinal study with a white cardboard handle within reach and a bright ball at the end of the handle and out of reach. A trick condition, where the handle and the ball seem attached but were not, was added to get an indication of the infant's expectation by observing a possible surprise reaction.Results show that 6-month-olds’ most frequent first behaviors consisted in pointing toward the ball without grasping the handle, or grasping the handle without looking at the ball until it moved. In addition, they often did not look surprised in the trick condition. Eight- and 10-month-olds most often grasped the handle while looking at the ball, and showed clear surprise in the trick condition. This was interpreted as showing that around eight or 10 months, infants take a significant step in understanding the cohesiveness of composite objects during grasping.