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.     

Young Infants' Performance in the Object‐Variation Version of the Above‐Below Categorization Task: A Result of Perceptual Distraction or Conceptual Limitation?

Five experiments were conducted to examine the performance of young infants on above versus below categorization tasks. Experiments 1 and 2 showed that infants did not form abstract categorical representations for above and below when familiarized with different objects depicted in a constant spatial relation relative to a horizontal bar and tested on a novel object depicted in the familiar and novel spatial relation. Experiments 3 through 5 examined perceptual‐attentional distraction versus conceptually based generalization explanations for young infant performance in the object‐variation version of the above‐below categorization task. Experiments 3 and 4 demonstrated that infants still did not form abstract categorical representations for above and below when object variation was removed from the familiarization trials or when object novelty was reduced during the preference test trials. However, Experiment 5 showed that 3‐ and 4‐month‐olds succeeded on the above versus below categorization task when familiarized with object variation and preference tested with a familiar versus novel object‐bar relation. These results indicate that young infants can form categorical representations for above and below in the object‐variation version of the above‐below categorization task, but that such representations are specific to the particular objects presented. Young infant performance in the object‐variation version of the above‐below categorization task thus reflects a conceptually based generalization limit rather than a problem of perceptual‐attentional distraction.     

A Comparison of Infants' Categorization in Paired and Successive Presentation Familiarization Tasks

Three experiments directly compared infants' categorization in variations of the visual familiarization task. In each experiment, 4‐ or 6‐month‐old infants were familiarized with a collection of dogs or cats and then their response to novel dogs and cats was assessed. In Experiment 1, 4‐month‐old infants responded to the exclusive distinction of dogs or cats when tested in a paired‐comparison task. In Experiments 2 and 3, 6‐month‐old infants, but not 4‐month‐old infants, responded to this same distinction in a successive presentation task, even when the amount of familiarization was equated to that of the paired comparison task. Therefore, familiarization with a particular set of stimuli does not induce infants to respond to a single category but rather they respond to different categories depending on features of the task.     

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.     

The Use of Pitch Accent in Word–Object Association by Monolingual Japanese Infants

This study investigated the lexical use of Japanese pitch accent in Japanese‐learning infants. A word–object association task revealed that 18‐month‐old infants succeeded in learning the associations between two nonsense objects paired with two nonsense words minimally distinguished by pitch pattern (Experiment 1). In contrast, 14‐month‐old infants failed (Experiment 2). Eighteen‐month‐old infants succeeded even for sounds that contained only the prosodic information (Experiment 3). However, a subsequent experiment revealed that 14‐month‐old infants succeeded in an easier single word–object task using pitch contrast (Experiment 4). These findings indicate that pitch pattern information is robustly available to 18‐month‐old Japanese monolingual infants in a minimal pair word‐learning situation, but only partially accessible in the same context for 14‐month‐old infants.     

Neural Correlates of Encoding Predict Infants’ Memory in the Paired‐Comparison Procedure

The present study used event‐related potentials (ERPs) to monitor infant brain activity during the initial encoding of a previously novel visual stimulus, and examined whether ERP measures of encoding predicted infants’ subsequent performance on a visual memory task (i.e., the paired‐comparison task). A late slow wave component of the ERP measured at encoding predicted infants’ immediate performance in the paired‐comparison task: amplitude of the late slow wave at right‐central and temporal leads decreased with stimulus repetition, and greater decreases at right‐anterior‐temporal leads during encoding were associated with better memory performance at test. By contrast, neither the amplitude nor latency of the negative central (Nc) component predicted infants’ subsequent performance in the paired‐comparison task. These findings are discussed with respect to a biased competition model of visual attention and memory.     

Infant Side Biases and Familiarity‐Novelty Preferences During a Serial Paired‐Comparison Task

We monitored changes in looking that emerged when 3‐ to 6‐month‐old infants were presented with 48 trials pairing familiar and novel faces. Graphic displays were used to identify changes in looking throughout the task. Many infants exhibited strong side biases produced by infants looking repeatedly in the same direction. Although an overall novelty preference was found for the group, individual infants exhibited brief novelty runs. Few infants began with a familiarity preference. We argue that variable looking patterns emerged during the task from competition between the infants' preference to look for something novel versus their tendency to look back to previous locations. Our data suggest that looking during paired‐comparison tasks is a dynamic process dependent on perceptual‐motor events happening during the task itself.     

Task‐to‐Task Vagal Regulation: Relations With Language and Play in 20‐Month‐Old Children

In this article we report patterns of task‐to‐task vagal tone change across multiple language and play tasks as well as associations between these patterns of task‐to‐task vagal tone change and language and play performance in 20‐month‐old girls and boys. Although initially different in vagal tone suppression during solitary play, girls and boys exhibited similar group patterns of vagal reengagement during successive language and play tasks with their mothers and with an experimenter. In terms of individual differences, vagal suppression during solitary play and vagal reengagement during social interactive tasks predicted language and play performance. Gender differences emerged in patterns of predictive relations: Task‐to‐task vagal changes predicted primarily play performance in girls and language performance in boys. These findings expose the effects of social context on directional changes in task‐to‐task vagal tone and speak to the functional role of appropriate vagal regulation in young children's language and play performance.     

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.     

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.     

Evaluation of the Psychometric Properties of the Gap‐Overlap Task in 10‐Month‐Old Infants

Understanding the development of attention is key to understanding cognitive maturation. The gap‐overlap task can be administered at all ages and is widely used to study the development of overt visual attention. However, studies using the gap‐overlap task report different measures and little is known about the tasks’ psychometric properties, especially in infants. We tested the 1‐week test–retest reliability of two frequently used gap‐overlap measures of attentional disengagement in 10‐month‐old infants; the gap effect as measured by the difference between the gap and overlap condition and the gap effect as measured by the difference between the gap and baseline condition. Sixty‐seven infants performed the gap‐overlap task twice, of which 45 infants had sufficient data quality for further analyses. Test–retest reliability of the overlap‐gap gap effect was higher (r = .50) than the baseline‐gap gap effect (r = .29). Moreover, the shared variance between overlap and baseline saccadic reaction times was moderate to high across sessions. In light of these results and the methodological challenges and limitations of infant research, we consider the overlap‐gap gap effect to be a good measure to study the development of attentional disengagement in infants and suggest the exclusion of the baseline condition in future studies.     

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.     

Exploring the Emergence of Side Biases and Familiarity–Novelty Preferences from the Real‐Time Dynamics of Infant Looking

This study examined how look dynamics contribute to infants’ emerging novelty preferences. Time‐series analyses were used to study the temporal nature of looking displayed by 3‐ to 5‐month‐old infants during a serial paired‐comparison task. Evidence was found only for short‐term stability: Novelty preferences and side biases were not stable from one visit to the next, but looking was consistent from one moment to the next producing stability within trials and temporarily across trials leading to the formation of behavioral runs. Persistence in looking left or right across multiple trials did not change from one visit to the next, but persistence in looking at familiar stimuli declined with age. By Visit 3, familiarity runs occurred less often than did novelty runs. Frequent but highly variable runs, including surprisingly late familiarity preferences, suggest that overall side biases and novelty preferences found during visual preference tasks are emergent phenomena affected by moment‐to‐moment changes in looking.     

Are You an Animal Too? US and Malawian Infants' Categorization of Plastic and Wooden Animal Replicas

In this study, we examined the effects of infant country and exemplar material on 24 US and 22 Malawian (African) 15‐month‐olds' categorization of animals versus vehicles. Following familiarization with either plastic or wooden animal replicas, infants were tested with objects of both materials in a standard object‐examining task. Both US and Malawian infants demonstrated category formation regardless of the material of the animal replicas. In addition, infants extended a category of plastic animals to novel wooden animals, but did not extend a category of wooden animals to novel plastic animals. These findings document a uniform impact of stimuli characteristics on infant object categorization despite differences in infant cultural background and toy animal experience. In addition, they show that, in some cases, infants can generalize their categorization of animals from one type of replica to another.     

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.     

Looking Behavior at Test and Relational Memory in 6‐Month‐Old Infants

Small‐scale eye‐tracking research lends support to behavioral studies of relational memory by 6 months of life. Here, in the largest eye‐tracking test of relational memory to date (n = 276), we replicate these findings and examine the impact of excluding data based on looking behavior characteristics at test. Past work examining infants' preferential looking toward arbitrary‐paired objects and scenes has excluded infants from analysis based upon “insufficient looking” at test. Yet, research suggests that variation in looking behavior may be associated with looking patterns during encoding, as well as trait‐like differences in visual and cognitive processing. Similar to past research, we observed evidence for relational memory among 6‐month‐olds. In keeping with past research, when infants were excluded based on “insufficient looking,” we observed evidence for relational memory only when infants were tested immediately. However, when exclusion criteria were relaxed, infants specifically demonstrated preferential looking during a presumably more difficult delay‐plus‐interference condition. Moreover, analyses revealed that looking behavior during encoding was associated with looking behavior at test. Together, results suggest that infants do possess rudimentary relational memory capabilities, but that experimenters' ability to detect these capabilities is influenced by both experimental conditions and individual differences in looking behavior.     

Learning While Babbling: Prelinguistic Object‐Directed Vocalizations Indicate a Readiness to Learn

Two studies illustrate the functional significance of a new category of prelinguistic vocalizing—object‐directed vocalizations (ODVs)—and show that these sounds are connected to learning about words and objects. Experiment 1 tested 12‐month‐old infants’ perceptual learning of objects that elicited ODVs. Fourteen infants’ vocalizations were recorded as they explored novel objects. Infants learned visual features of objects that elicited the most ODVs but not of objects that elicited the fewest vocalizations. Experiment 2 assessed the role of ODVs in learning word–object associations. Forty infants aged 11.5 months played with a novel object and received a label either contingently on an ODV or on a look alone. Only infants who received labels in response to an ODV learned the association. Taken together, the findings suggest that infants’ ODVs signal a state of attention that facilitates learning.     

Twelve‐Month‐Olds Understand Social Intentions Based on Prosody and Gesture Shape

Infants infer social and pragmatic intentions underlying attention‐directing gestures, but the basis on which infants make these inferences is not well understood. Previous studies suggest that infants rely on information from preceding shared action contexts and joint perceptual scenes. Here, we tested whether 12‐month‐olds use information from act‐accompanying cues, in particular prosody and hand shape, to guide their pragmatic understanding. In Experiment 1, caregivers directed infants’ attention to an object to request it, share interest in it, or inform them about a hidden aspect. Caregivers used distinct prosodic and gestural patterns to express each pragmatic intention. Experiment 2 was identical except that experimenters provided identical lexical information across conditions and used three sets of trained prosodic and gestural patterns. In all conditions, the joint perceptual scenes and preceding shared action contexts were identical. In both experiments, infants reacted appropriately to the adults’ intentions by attending to the object mostly in the sharing interest condition, offering the object mostly in the imperative condition, and searching for the referent mostly in the informing condition. Infants’ ability to comprehend pragmatic intentions based on prosody and gesture shape expands infants’ communicative understanding from common activities to novel situations for which shared background knowledge is missing.     

Word Level Stress and Lexical Processing in 17‐Month‐Old Infants

Detailed representations enable infants to distinguish words from one another and more easily recognize new words. We examined whether 17‐month‐old infants encode word stress in their familiar word representations. In Experiment 1, infants were presented with pairs of familiar objects while hearing a target label either properly pronounced with the correct stress (e.g., baby /’be?bi/) or mis‐pronounced with the incorrect stress pattern (e.g., baby /be?’bi/). Infants mapped both the correctly stressed and mis‐stressed labels to the target objects; however, they were slower to fixate the target when hearing the mis‐stressed label. In Experiment 2, we examined whether infants appreciate that stress has a nonproductive role in English (i.e., altering the stress of a word does not typically signal a change in word meaning) by presenting infants with a familiar object paired with a novel object while hearing either correctly stressed or mis‐stressed familiar words (Experiment 2). Here, infants mapped the correctly stressed label to the familiar object but did not map the mis‐stressed label reliably to either the target or distractor objects. These findings suggest that word stress impacts the processing of familiar words, and infants have burgeoning knowledge that altering the stress pattern of a familiar word does not reliably signal a new referent.     

Where Infants Look Determines How They See: Eye Movements and Object Perception Performance in 3‐Month‐Olds

A fundamental question of perceptual development concerns how infants come to perceive partly hidden objects as unified across a spatial gap imposed by an occluder. Much is known about the time course of development of perceptual completion during the first several months after birth, as well as some of the visual information that supports unity perception in infants. The goal of this investigation was to examine the inputs to this process. We recorded eye movements in 3‐month‐old infants as they participated in a standard object unity task and found systematic differences in scanning patterns between those infants whose post‐habituation preferences were indicative of unity perception versus those infants who did not perceive unity. Perceivers, relative to nonperceivers, scanned more reliably in the vicinity of the visible rod parts and scanned more frequently across the range of rod motion. These results suggest that emerging object concepts are tied closely to available visual information in the environment, and the process of information pickup.