Crawling is Associated with Mental Rotation Ability by 9‐Month‐Old Infants

The present experiment examined whether 9‐month‐old infants’ mental rotation ability was related to their crawling ability. Forty‐eight 9‐month‐old infants were tested; half of them crawled for 7.1 weeks on average. Infants were habituated to a video of a simplified Shepard–Metzler object rotating back and forth through a 240° angle around the longitudinal axis of the object. Infants were tested with videos of the same object rotating through the previously unseen 120° angle and with the mirror image of that display. The results showed that the crawlers looked significantly longer at the mirror object than at the familiar object. The results support the interpretation that crawling experience is associated with 9‐month‐old infants’ mental rotation ability.     

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. This 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.     

A Sex Difference in Mental Rotation in Infants: Convergent Evidence

Quinn and Liben (2008) reported a sex difference on a mental rotation task in which 3‐ to 4‐month‐olds were familiarized with a shape in different rotations and then tested with a novel rotation of the familiar shape and its mirror image. As a group, males but not females showed a significant preference for the mirror image, a pattern paralleled at the individual level (with most males but less than half the females showing the preference). Experiment 1 examined a possible explanation for this performance difference, namely, that females were more sensitive to the angular differences in the familiarized shape. Three‐ to 4‐month‐olds were given a discrimination task involving familiarization with a shape at a given rotation and preference testing with the shape in the familiarized versus a novel rotation. Females and males preferred the novel rotation, with no sex difference observed. This finding did not provide support for the suggestion that the sex difference in mental rotation is explained by differential sensitivity to angular rotation. Experiment 2 revealed that the sex difference in mental rotation is observed in 6‐ to 7‐month‐olds and 9‐ to 10‐month‐olds, suggesting that a sex difference in mental rotation is present at multiple ages during infancy.     

Relating 7‐Month‐Olds Visuo‐Spatial Working Memory to Other Basic Mental Skills Assessed With Two Different Versions of the Habituation–Dishabituation Paradigm

This study examines the relationship between various basic mental processing abilities in infancy. Two groups of 7‐month‐olds received the same delayed‐response task to assess visuo‐spatial working memory, but two different habituation–dishabituation tasks to assess processing speed and recognition memory. The single‐stimulus group (N = 32) was familiarized with only one abstract stimulus, whereas the categorization group (N = 32) received varying exemplars of the same kind. In the categorization group, infants high on working memory showed stronger habituation and dishabituation responses than infants scoring low in working memory. No corresponding relations were found for the single‐stimulus group. This suggests that working memory performance is systematically linked to other basic mental skills in 7‐month‐olds, but that corresponding relations may not get evident in any kind of habituation–dishabituation procedure. Implications for understanding the complex interplay of basic mental abilities in infancy will be discussed.     

Picture Perception in Infants: Do 9‐Month‐Olds Attempt to Grasp Objects Depicted in Photographs?

Two experiments tested the DeLoache, Pierroutsakos, Uttal, Rosengren, and Gottlieb (1998 claim that 9‐month‐old infants attempt to grasp objects depicted in photographs. In Experiment 1, 9‐month‐olds viewed an object, a photograph of the object, and 2 flat, nonpictorial displays. On average, they reached for the photograph and nonpictorial displays with their hands approximately horizontal and close to the display surfaces, but reached for the object with their hands oriented obliquely and at significantly higher heights. The infants also exhibited similar behaviors when touching the photograph and nonpictorial displays. In Experiment 2, 9‐month‐olds exhibited similar behaviors when touching a photograph of an object and a photograph of textured carpet. The results of both experiments suggest that 9‐month‐olds treat photographs of objects as 2‐dimensional surfaces and not as graspable objects.     

Intersensory Redundancy and 7‐Month‐Old Infants' Memory for Arbitrary Syllable‐Object Relations

Seven‐month‐old infants require redundant information, such as temporal synchrony, to learn arbitrary syllable‐object relations (Gogate & Bahrick, 1998). Infants learned the relations between 2 spoken syllables, /a/ and /i/, and 2 moving objects only when temporal synchrony was present during habituation. This article presents 2 experiments to address infants' memory for these relations. In Experiment 1, infants remembered the syllable‐object relations after 10 min, only when temporal synchrony between the vocalizations and moving objects was provided during learning. In Experiment 2, 7‐month‐olds were habituated to the same syllable‐object pairs in the presence of temporal synchrony and tested for memory after 4 days. Once again, infants learned and showed emerging memory for the syllable‐object relations 4 days after original learning under the temporally synchronous condition. These findings are consistent with the view that prior to symbolic development, infants learn and remember word‐object relations by perceiving redundant information in the vocal and gestural communication of adults.     

Object Permanence in Five‐and‐a‐Half‐Month‐Old Infants?

Event Set × Event Set designs were used to study the rotating screen paradigm introduced by Baillargeon, Spelke, and Wasserman (1985). In Experiment 1, 36 5 1/2‐month‐old infants were habituated to a screen rotating 180° with no block, a screen rotating 120° up to a block, or a screen rotating 180° up to and seemingly through a block. All infants were then tested on the same 3 events and also a screen rotating 120° with no block. The results indicate that infants are using novelty and familiarity preference to determine their looking times. To confirm this, in Experiment 2, 52 5 1/2‐month‐old infants were familiarized on either 3 or 7 trials to a screen rotating 180° with no block or a screen rotating 120° with no block. All infants were then tested on the same test events as in Experiment 1. Infants with fewer familiarization trials were more likely to prefer the familiar rotation event. The results of these 2 experiments indicate that infants did not use the possibility or impossibility of events but instead used familiarity or novelty relations between the habituation events and the test events to determine their looking times, and suggest that the Baillargeon et al. study should not be interpreted as indicating object permanence or solidity knowledge in young infants.     

Eight‐Month‐Old Infants' Perception of Possible and Impossible Events

This study investigated 8‐month‐old infants' perception of object permanence in an extension of the rotating screen studies by Baillargeon (1987) and Baillargeon, Spelke, and Wasserman (1985). Using computer‐animated stimuli similar to the “live” stimuli used by Baillargeon and her colleagues (Baillargeon, 1987; Baillargeon et al., 1985), 48 8‐month‐old infants were habituated to 1 of 4 computer‐animated events and then tested on all 4 events. The events involved a screen that rotated in either a 180° or 120° arc*** and a block that either was sitting in the path of the rotating screen or absent from the event. The results provided no evidence that infants responded on the basis of the possibility or impossibility of the events as claimed by Baillargeon and her colleagues, but instead indicated that the infants responded on the basis of perceptual novelty. These results are consistent with the findings of Schilling (this issue) and Bogartz, Shinskey, and Schilling (this issue). Taken together, along with the findings of Rivera, Wakeley, and Langer (1999), these more recent findings suggest that Baillargeon's (1987; Baillargeon et al., 1985) results should not be interpreted as definitive evidence of object permanence in very young infants.     

Infants Discriminate the Affective Expressions of their Peers: The Roles of Age and Familiarization Time

Research examining infants’ discrimination of affect often uses unfamiliar faces and voices of adults. Recently, research has examined infant discrimination of affect in familiar faces and voices. In much of this research, infants were habituated to the affective expressions using a “standard” 50% habituation criterion. We extend this line of research by examining infants’ discrimination of unfamiliar peers’, that is, 4‐month‐olds, dynamic, facial, and vocal affective expressions and assessing how discrimination is affected by changing the habituation criterion. In two experiments, using an infant‐controlled habituation design, we explored 3‐ and 5‐month‐olds’ discrimination of their peers’ dynamic audiovisual displays of positive and negative expressions of affect. Results of Experiment 1, using a 50% habituation criterion, revealed that 5‐month‐olds, but not 3‐month‐olds discriminated the affective expressions of their peers. In Experiment 2, we examined whether 3‐month‐olds’ lack of discrimination in Experiment 1 was a result of insufficient habituation (i.e., familiarization). Specifically, 3‐month‐olds were habituated using a 70% habituation criterion, providing them with longer familiarization time. Results revealed that using the more stringent habituation criterion, 3‐month‐olds showed longer habituation times, that is increased familiarization, and discriminated their peers’ affective expressions. Results are discussed in terms of infants’ discrimination of affect, the role of familiarization time, and limitations of the 50% habituation criterion.     

Six‐ and 9‐Month‐Old Infants Discriminate Between Goals Despite Similar Action Patterns

Behne, Carpenter, Call, and Tomasello (2005) showed that 9‐ to 18‐month‐olds, but not 6‐month‐olds, differentiated between people who were unwilling and unable to share toys. As the outcome of the two tasks is the same (i.e., the toy is not shared), the infants must respond to the different goals of the actor. However, visual habituation paradigms have shown an earlier onset of goal awareness. The present study reconciles this disparity by replicating the findings of Behne et al. with both 6‐ and 9‐month‐olds, using similar tasks and additional response measures.     

Evidence of the Face Inversion Effect in 4‐Month‐Old Infants

This study tested the presence of the face inversion effect in 4‐month‐old infants using habituation to criterion followed by a novelty preference paradigm. Results of Experiment 1 confirmed previous findings, showing that when 1 single photograph of a face is presented in the habituation phase and when infants are required to recognize the same photograph, no differences in recognition performance with upright and inverted faces are found. However, Experiment 2 showed that, when infants are habituated to a face shown in a variety of poses and are required to recognize a new pose of the same face, infants' recognition performances were higher for upright than for inverted faces. Overall, results indicate that, under some experimental conditions, 4‐month‐olds process faces differently according to whether faces are presented upright or inverted.     

Mechanisms of Visual Object Recognition in Infancy: Five‐Month‐Olds Generalize Beyond the Interpolation of Familiar Views

This work examined predictions of the interpolation of familiar views (IFV) account of object recognition performance in 5‐month‐olds. Infants were familiarized to an object either from a single viewpoint or from multiple viewpoints varying in rotation around a single axis. Object recognition was then tested in both conditions with the same object rotated around a novel axis. Infants in the multiple‐views condition recognized the object, whereas infants in the single‐view condition provided no evidence for recognition. Under the same 2 familiarization conditions, infants in a 2nd experiment treated as novel an object that differed in only 1 component from the familiar object. Infants' object recognition is enhanced by experience with multiple views, even when that experience is around an orthogonal axis of rotation, and infants are sensitive to even subtle shape differences between components of similar objects. In general, infants' performance does not accord with the predictions of the IFV model of object recognition. These findings motivate the extension of future research and theory beyond the limits of strictly interpolative mechanisms.     

A Global‐to‐Basic Trend in Early Categorization: Evidence From a Dual‐Category Habituation Task

A series of 3 experiments are reviewed in which infants between 4 and 10 months of age were familiarized with members of 2 basic‐level object categories. The degree of distinctiveness between categories was varied. Preference tests were intended to determine whether infants formed a single category representation (at a more global level) or 2 basic‐level representations. Across 3 experiments, 10‐month‐old infants appeared to have formed multiple basic‐level categories, whereas younger infants tended to form broader, more inclusive representations. The tendency to form multiple categories was influenced to some extent by category distinctiveness. Whereas 10‐month‐olds formed separate categories for all contrasts, 7‐month‐olds did so only when the 2 familiarized categories were from separate global domains. A perceptual account of the global‐to‐basic shift in early categorization is offered. Task dependencies in early categorization are also discussed.     

Infants' Sensitivity to the Causal Features of Means‐End Support Sequences in Action and Perception

Current work has yielded differential findings regarding infants' ability to perceptually detect the causal structure of a means‐end support sequence. Resolving this debate has important implications for perception‐action dissociations in this domain of object knowledge. In Study 1, 12‐month‐old infants' ability to perceive the causal structure of a cloth‐pulling sequence was assessed via a habituation paradigm. After seeing an event in which a supported toy was moved by pulling a cloth that it sat on, 12‐month‐old infants demonstrated longer looking to events that violated the causal structure of this sequence than to events that preserved the causal structure but varied other perceptual features of the event. Studies 2 and 3 investigated 10‐month‐olds' interpretations of means‐end support sequences using both a habituation paradigm and a task that assessed infants' own means‐end actions. Whereas 10‐month‐olds failed to demonstrate an understanding of the causal structure when tested using a flat cloth as the support (Study 2), sensitivity to this structure was apparent when a rectangular box was the support. These patterns were evident in both action and perception (Study 3). Moreover, individual variation in action task performance was related to visual habituation performance. The results are discussed with respect to the relation between action and perception in infancy.     

14‐Month‐olds anticipate others’ actions based on their belief about an object's identity

Past research has accumulated evidence regarding infants’ false‐belief understanding, measuring their gaze patterns or active helping behaviors. However, the underlying mechanisms are still debated, specifically, whether young infants can compute that others represent the world under a certain aspect. Such performance requires holding in mind two representations about the same object simultaneously and attributing only one to another person. While 14‐month‐olds can encode an object under different aspects when forming first‐person representations, it is unclear whether infants at this very age could also predict others’ behavior based on their beliefs about an object's identity. Here, we investigate this question in a novel eye‐tracking‐based unexpected‐identity task. We measured 14‐month‐olds’ anticipatory looks combined with their looking time, using a violation‐of‐expectation paradigm. Results show that 14‐month‐olds look longer to an actor's reach that is incongruent with her false belief about the identity of an object compared to a congruent reach. Furthermore, infants correctly anticipated the actor's reach based on her false belief. Thus, as soon as infants represent dual identities they can integrate them in belief attributions and use them for consequent behavioral predictions. Such data provide evidence for the flexibility of false‐belief attributions and support proposals arguing for infants’ rich theory‐of‐mind abilities.     

5‐Month‐Olds’ Categorization of Novel Objects: Task and Measure Dependence

To examine key parameters of the initial conditions in early category learning, two studies compared 5‐month‐olds’ object categorization between tasks involving previously unseen novel objects, and between measures within tasks. Infants in Experiment 1 participated in a visual familiarization–novelty preference (VFNP) task with two‐dimensional (2D) stimulus images. Infants provided no evidence of categorization by either their looking or their examining even though infants in previous research systematically categorized the same objects by examining when they could handle them directly. Infants in Experiment 2 participated in a VFNP task with 3D stimulus objects that allowed visual examination of objects’ 3D instantiation while denying manual contact with the objects. Under these conditions, infants demonstrated categorization by examining but not by looking. Focused examination appears to be a key component of young infants’ ability to form category representations of novel objects, and 3D instantiation appears to better engage such examining.     

The Influence of Labels,Non‐Labeling Sounds,and Source of Auditory Input on 9‐ and 15‐Month‐Olds' Object Categorization

This experiment examines the joint influence of auditory and social cues on infants' basic‐level and global categorization. Nine‐ and fifteen‐month‐olds were familiarized to a series of category exemplars in an object‐examining task. Objects were introduced with a labeling phrase, a non‐labeling sound, or no sound, and auditory input was presented orally by the experimenter or played on a hidden voice recorder. Novel objects from the familiarized category and a contrasting category were then presented. Results of analyses performed on novelty preference scores indicated that infants demonstrated basic‐level categorization in all conditions. However, infants at both age levels only demonstrated global categorization when labeling phrases were introduced. In addition, labels led to global categorization in 9‐month‐olds regardless of the source of those labels; however, labels only led to global categorization in 15‐month‐olds when the labels were presented orally by the experimenter.     

Infant Perception of Surface Texture and Relative Height as Distance Information: A Preferential‐Reaching Study

Two preferential‐reaching experiments explored 5‐ and 7‐month‐olds’ sensitivity to pictorial depth cues. In the first experiment, infants viewed a display in which texture gradients, linear perspective of the surface contours, and relative height in the visual field provided information that two objects were at different distances. Five‐ and 7‐month‐old infants reached preferentially for the apparently nearer object under monocular but not binocular viewing conditions, indicating that infants in both age groups respond to pictorial depth cues. In the second experiment, texture gradients and linear perspective of the surface contours were eliminated from the experimental display, making relative height the sole pictorial depth cue. Seven‐month‐olds again reached more often for the apparently nearer object under monocular, but not binocular viewing conditions. By contrast, the 5‐month‐olds’ reaching behavior did not differ between viewing conditions. These results indicate that 7‐month‐olds respond to the depth cue of relative height but provide no evidence of responsiveness to relative height in 5‐month‐olds. Both age groups responded more consistently to pictorial depth in Experiment 1 than in Experiment 2.     

The Other‐Race Effect in a Longitudinal Sample of 3‐, 6‐ and 9‐Month‐Old Infants: Evidence of a Training Effect

We investigated the development of the other‐race effect “ORE” in a longitudinal sample of 3‐, 6‐, and 9‐month‐old Caucasian infants. Previous research using cross‐sectional samples has shown an unstable ORE at 3 months, an increase at 6 months and full development at 9 months. In Experiment 1, we tested whether 9‐month‐olds showed the ORE with Caucasian and African faces. As expected, the 9‐month‐olds discriminated faces within their own ethnicity (Caucasian) but not within the unfamiliar ethnicity (African). In months. In Experiment 2, we longitudinally tested infants at 3, 6, and 9 months by presenting either the Caucasian or the African faces used in Experiment 1. In contrast to previous cross‐sectional studies and Experiment 1, we found that infants discriminated between all stimuli. Hence, we did not find the ORE in this longitudinal study even at 9 months. We assume that the infants in our longitudinal study showed no ORE because of previous repetitive exposure to African faces at 3 and 6 months. We argue that only a few presentations of faces from other ethnic categories sufficiently slow the development of the ORE.     

Second‐Order Correlation Learning of Dynamic Stimuli: Evidence from Infants and Computational Modeling

We present two habituation experiments that examined 20‐ and 26‐month‐olds’ ability to engage in second‐order correlation learning for static and dynamic features, whereby learned associations between two pairs of features (e.g., P and Q, P and R) are generalized to the features that were not presented together (e.g., Q and R). We also present results from an associative learning mechanism that was implemented as an autoencoder parallel distributed processing (PDP) network in which second‐order correlation learning is shown to be an emergent property of the dynamics of the network. The experiments and simulation demonstrate that 20‐ and 26‐month‐olds as well as neural networks are capable of second‐order correlation learning in a category context for internal features of dynamic objects. However, the model predicts—and Experiment 3 demonstrates—that 20‐ and 26‐month‐olds are unable to encode second‐order correlations in a noncategory context for dynamic objects with internal features. It is proposed that the ability to learn second‐order correlations represents a powerful but as yet unexplored process for generalization in the first years of life.