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.     

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.     

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.     

Postural Position Constrains Multimodal Object Exploration in Infants

Recent research has revealed the important role of multimodal object exploration in infants' cognitive and social development. Yet, the real‐time effects of postural position on infants' object exploration have been largely ignored. In the current study, 5‐ to 7‐month‐old infants (N = 29) handled objects while placed in supported sitting, supine, and prone postures, and their spontaneous exploratory behaviors were observed. Infants produced more manual, oral, and visual exploration in sitting compared to lying supine and prone. Moreover, while sitting, infants more often coupled manual exploration with mouthing and visual examination. Infants' opportunities for learning from object exploration are embedded within a real‐time postural context that constrains the quantity and quality of exploratory behavior.     

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.     

The Effects of Graded Occlusion on Manual Search and Visual Attention in 5‐ to 8‐Month‐Old Infants

Young infants may be limited in searching for hidden objects because they lack the means‐end motor skill to lift occluders from objects. This account was investigated by presenting 5‐ to 8‐month‐old infants with objects hidden behind transparent, semitransparent, and opaque curtains. If a means—end deficit explains search limitations, then infants should search no more for an object behind a transparent curtain than for objects behind semitransparent or opaque curtains. However, level of occlusion had a significant effect on manual search and visual attention. Infants retrieved and contacted the object more, contacted the curtain more, and looked away less with the transparent curtain than with the semi transparent or opaque curtains. Adding a time delay before allowing search and presenting a distraction after occlusion further depressed infants' behavior. The findings fail to support the means—end deficit hypothesis, but are consistent with the account that young infants lack object permanence.     

Attention to Maternal Multimodal Naming by 6‐ to 8‐Month‐Old Infants and Learning of Word–Object Relations

We examined whether mothers' use of temporal synchrony between spoken words and moving objects, and infants' attention to object naming, predict infants' learning of word–object relations. Following 5 min of free play, 24 mothers taught their 6‐ to 8‐month‐olds the names of 2 toy objects, Gow and Chi, during a 3‐min play episode. Infants were then tested for their word mapping. The videotaped episodes were coded for mothers' object naming and infants' attention to different naming types. Results indicated that mothers' use of temporal synchrony and infants' attention during play covaried with infants' word‐mapping ability. Specifically, infants who switched eye gaze from mother to object most frequently during naming learned the word–object relations. The findings suggest that maternal naming and infants' word‐mapping abilities are bidirectionally related. Variability in infants' attention to maternal multimodal naming explains the variability in early lexical‐mapping development.     

Mental Rotation of Dynamic,Three‐Dimensional Stimuli by 3‐Month‐Old Infants

Mental rotation involves transforming a mental image of an object so as to accurately predict how the object would look if it were rotated in space. This study examined mental rotation in male and female 3‐month‐olds, using the stimuli and paradigm developed by Moore and Johnson (2008) . Infants were habituated to a video of a three‐dimensional object rotating back and forth through a 240° angle around the vertical axis. After habituation, infants were tested both with videos of the same object rotating through the previously unseen 120° angle, and with the mirror image of that display. Unlike females, who fixated the test displays for approximately equal durations, males spent significantly more time fixating the familiar object than the mirror‐image object. Because familiarity preferences like this emerge when infants are relatively slow to process a habituation stimulus, the data support the interpretation that mental rotation of dynamic three‐dimensional stimuli is relatively difficult—but possible—for 3‐month‐old males. Interpretation of the sex differences observed in 3‐ and 5‐month‐olds’ performances is discussed.     

Six‐Month‐Old Infants Predict Agents’ Goal‐Directed Actions on Occluded Objects

Infants can infer agents’ goals after observing agents’ goal‐directed actions on objects and can subsequently make predictions about how agents will act on objects in the future. We investigated the representations supporting these predictions. We familiarized 6‐month‐old infants to an agent who preferentially reached for one of two featurally distinct objects following a cue. At test, the objects were sequentially occluded from the infant in the agent's presence. We asked whether infants could generate action predictions without visual access to the relevant objects by measuring whether infants shifted their gaze to the location of the agent's hidden goal object following the cue. We also examined what infants represented about the hidden objects by removing one of the occluders to reveal either the original hidden object or the unexpected other object and measuring infants’ looking time. We found that, even without visual access to the objects, infants made predictive gazes to the location of the agent's occluded goal object, but failed to represent the features of either hidden object. These results suggest that infants make goal‐based action predictions when the relevant objects in the scene are occluded, but doing so may come at the expense of maintaining representations of the objects.     

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.     

Infants' Evolving Representations of Object Motion During Occlusion: A Longitudinal Study of 6‐ to 12‐Month‐Old Infants

Infants' ability to track temporarily occluded objects that moved on circular trajectories was investigated in 20 infants using a longitudinal design. They were first seen at 6 months and then every 2nd month until the end of their 1st year. Infants were presented with occlusion events covering 20% of the target's trajectory (effective occlusion interval ranged from 500–4,000 msec). Gaze was measured using an ASL 504 infrared eye‐tracking system. Results effectively demonstrate that infants from 6 months of age can represent the spatiotemporal dynamics of occluded objects. Infants at all ages tested were able to predict, under certain conditions, when and where the object would reappear after occlusion. They moved gaze accurately to the position where the object was going to reappear and scaled their timing to the current occlusion duration. The average rate of predictive gaze crossings increased with occlusion duration. These results are discussed as a 2‐factor process. Successful predictions are dependent on strong representations, themselves dependent on the richness of information available during encoding and graded representations.     

Infants’ Response to Pictures of Impossible Objects

Previous work has shown that 4‐month‐olds can discriminate between two‐dimensional (2D) depictions of structurally possible and impossible objects [S. M. Shuwairi (2009), Journal of Experimental Child Psychology, 104, 115; S. M. Shuwairi, M. K. Albert, & S. P. Johnson (2007), Psychological Science, 18, 303]. Here, we asked whether evidence of discrimination of possible and impossible pictures would also be revealed in infants’ patterns of reaching and manual exploration. Nine‐month‐old infants were presented with realistic photograph displays of structurally possible and impossible cubes along with a series of perceptual controls, and engaged in more frequent manual exploration of pictures of impossible objects. In addition, the impossible cube display elicited significantly more social referencing and vocalizations than the possible cube and perceptual control displays. The increased manual gestures associated with the incoherent figure suggest that perceptual and manual action mechanisms are interrelated in early development. The infant’s visual system extracts structural information contained in 2D images in analyzing the projected 3D configuration, and this information serves to control both the oculomotor and manual action systems.     

The emergence of object‐based visual attention in infancy: A role for family socioeconomic status and competing visual features

The development of spatial visual attention has been extensively studied in infants, but far less is known about the emergence of object‐based visual attention. We tested 3–5‐ and 9–12‐month‐old infants on a task that allowed us to measure infants’ attention orienting bias toward whole objects when they competed with color, motion, and orientation feature information. Infants’ attention orienting to whole objects was affected by the dimension of the competing visual feature. Whether attention was biased toward the whole object or its salient competing feature (e.g., “ball” or “red”) changed with age for the color feature, with infants biased toward whole objects with age. Moreover, family socioeconomic status predicted feature‐based attention in the youngest infants and object‐based attention in the older infants when color feature information competed with whole‐object information.     

Fine‐Grained Analysis of Motionese: Eye Gaze,Object Exchanges,and Action Units in Infant‐Versus Adult‐Directed Action

Mothers modify their actions when demonstrating objects to infants versus adults. Such modifications have been called infant‐directed action (IDA) or motionese (Brand, Baldwin, & Ashburn, 2002). We investigated the IDA features of interactiveness and simplification by quantifying eye gaze, object exchanges, and action units enacted between exchanges in 42 mothers' demonstrations of novel objects to infants (6–8 months or 11–13 months) or adults. We found more eye gaze, more object exchanges, and fewer action types per turn in demonstrations to infants relative to adults. Unlike prior research using global measurements, we detected differences in behavior directed at infants of different ages: Shorter, more frequent gazes and more exchanges characterized demonstrations to older versus younger infants. These findings indicate the fruitfulness of fine‐grained analysis of IDA, and further clarify how adults may support infants' processing of human motion.     

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.     

A Cross‐Linguistic Study of Word‐Mapping in 18‐ to 20‐Month‐Old Infants

This study was designed to examine whether infants acquiring languages that place a differential emphasis on nouns and verbs, focus their attention on motions or objects in the presence of a novel word. An infant‐controlled habituation paradigm was used to teach 18‐ to 20‐month‐old English‐, French‐, and Japanese‐speaking infants’ novel words for events. Infants were habituated to two word‐event pairings and then presented with new combinations that involved a familiar word with a new object or motion, or both. Children could map the novel word to both the object and the motion, despite the differential salience of object and motion words in their native language. A control experiment with no label confirmed that both object and motion changes were detectable.     

Gaze following in 4.5‐ and 6‐month‐old infants: The impact of proximity on standard gaze following performance tests

Gaze following (GF), the ability to synchronize visual attention with others, is often considered a foundation of social cognition. In this study, GF was assessed while changing the space between an actor's eyes and the gaze target. This was done to address a potential confound in the gold standard GF performance test, namely the spatial bias of the actors’ eye position that occurs when the actor turns the head to look at a target, offsetting the eye position from a centered position toward the attended target. Our results suggest that both 4.5 (n = 27) and 6 (n = 30)‐month‐old infants can follow an actor's gaze regardless of proximity. This is the first demonstration that early GF is not dependent on proximity cues, and our results strengthen previous findings suggesting that GF develops well before 6 months of age. The study was preregistered, and all data and analysis routines can be downloaded with provided links.     

12‐Month‐Old Infants' Perception of Attention Direction in Static Video Images

Twelve‐month‐old infants' ability to perceive gaze direction in static video images was investigated. The images showed a woman who performed attention‐directing actions by looking or pointing toward 1 of 4 objects positioned in front of her (2 on each side). When the model just pointed at the objects, she looked straight ahead, and when she just looked, her hands were hidden below the tabletop. An eye movement system (TOBII) was used to register the gaze of the participants. We found that the infants clearly discriminated the gaze directions to the objects. There was no tendency to mix up the 2 object positions, located 10° apart, on the same side of the model. The infants spent more time looking at the attended objects than the unattended ones and they shifted gaze more often from the face of the model to the attended object than to the unattended objects. Pointing did not significantly increase the infants' tendency to move gaze to the attended object, irrespective of whether the pointing gesture was accompanied by looking or not. In all conditions the infants spent most of the time looking at the model's face. This tendency was especially noticeable in the pointing‐only condition and the condition where the model just looked straight ahead.     

Learned Labels Shape Pre‐speech Infants’ Object Representations

Infants rapidly learn both linguistic and nonlinguistic representations of their environment and begin to link these from around 6 months. While there is an increasing body of evidence for the effect of labels heard in‐task on infants’ online processing, whether infants’ learned linguistic representations shape learned nonlinguistic representations is unclear. In this study 10‐month‐old infants were trained over the course of a week with two 3D objects, one labeled, and one unlabeled. Infants then took part in a looking time task in which 2D images of the objects were presented individually in a silent familiarization phase, followed by a preferential looking trial. During the critical familiarization phase, infants looked for longer at the previously labeled stimulus than the unlabeled stimulus, suggesting that learning a label for an object had shaped infants’ representations as indexed by looking times. We interpret these results in terms of label activation and novelty response accounts and discuss implications for our understanding of early representational development.     

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.