The Emergence and Stability of the Attentional Bias to Fearful Faces in Infancy

Several studies have shown that at 7 months of age, infants display an attentional bias toward fearful facial expressions. In this study, we analyzed visual attention and heart rate data from a cross‐sectional study with 5‐, 7‐, 9‐, and 11‐month‐old infants (Experiment 1) and visual attention from a longitudinal study with 5‐ and 7‐month‐old infants (Experiment 2) to examine the emergence and stability of the attentional bias to fearful facial expressions. In both experiments, the attentional bias to fearful faces appeared to emerge between 5 and 7 months of age: 5‐month‐olds did not show a difference in disengaging attention from fearful and nonfearful faces, whereas 7‐ and 9‐month‐old infants had a lower probability of disengaging attention from fearful than nonfearful faces. Across the age groups, heart rate (HR) data (Experiment 1) showed a more pronounced and longer‐lasting HR deceleration to fearful than nonfearful expressions. The results are discussed in relation to the development of the perception and experience of fear and the interaction between emotional and attentional processes.     

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.     

Infants Experience Perceptual Narrowing for Nonprimate Faces

Perceptual narrowing—a phenomenon in which perception is broad from birth, but narrows as a function of experience—has previously been tested with primate faces. In the first 6 months of life, infants can discriminate among individual human and monkey faces. Though the ability to discriminate monkey faces is lost after about 9 months, infants retain human face discrimination, presumably because of their experience with human faces. The current study demonstrates that 4‐ to 6‐month‐old infants are able to discriminate nonprimate faces as well. In a visual paired comparison test, 4‐ to 6‐month‐old infants (n = 26) looked significantly longer at novel sheep (Ovis aries) faces, compared to a familiar sheep face (p = .017), while 9‐ to 11‐month‐olds (n = 26) showed no visual preference, and adults (n = 27) had a familiarity preference (p < .001). Infants’ face recognition systems are broadly tuned at birth—not just for primate faces, but for nonprimate faces as well—allowing infants to become specialists in recognizing the types of faces encountered in their first year of life.     

Motion Popout in Selective Visual Orienting at 4.5 But Not at 2 Months in Human Infants

The effect of element density on selective orienting was examined in 2 experiments with 2‐ and 4.5‐month‐old infants. Selective visual orienting to a singleton oscillating target that appeared with other static bars was used to study the effects of element density. Increasing the set size and density of the static bars decreased selective orienting to the moving target in the 2‐month‐old infants, but it increased selective orienting in the 4.5‐month‐olds despite the fact that the overall levels of correct orienting to the target were titrated to be the same at the 2 ages. Thus, density affected the selectivity of visual orienting to movement at these 2 ages differently with popout being evident at the older age. In the 2nd experiment, motion popout for the 4.5‐month‐old infants was replicated using oscillating targets that had the same peak and mean speeds but different temporal frequencies and amplitudes of oscillation. Increases in the efficiency of perceptual grouping of similar elements between 2 and 4.5 months of age could overcome the lateral masking effects of increasing element density seen at the lower end of this age range.     

Emergence of a consonant bias during the first year of life: New evidence from own‐name recognition

Recent evidence suggests that during the first year of life, a preference for consonant information during lexical processing (consonant bias) emerges, at least for some languages like French. Our study investigated the factors involved in this emergence as well as the developmental consequences for variation in consonant bias emergence. In a series of experiments, we measured 5‐, 8‐, and 11‐month‐old French‐learning infants orientation times to a consonant or vowel mispronunciation of their own name, which is one of the few word forms familiar to infants at this young age. Both 5‐ and 8‐month‐olds oriented longer to vowel mispronunciations, but 11‐month‐olds showed a different pattern, initially orienting longer to consonant mispronunciations. We interpret these results as further evidence of an initial vowel bias, with consonant bias emergence by 11 months. Neither acoustic‐phonetic nor lexical factors predicted preferences in 8‐ and 11‐month‐olds. Finally, counter to our predictions, a vowel bias at the time of test for 11‐month‐olds was related to later productive vocabulary outcomes.     

Speed of Processing and Face Recognition at 7 and 12 Months

This research examined developmental and individual differences in infants' speed of processing faces and the relation of processing speed to the type of information encoded. To gauge processing speed, 7‐ and 12‐month‐olds were repeatedly presented with the same face (frontal view), each time paired with a new one, until they showed a consistent preference for the new one. Subsequent probe trials assessed recognition of targets that either preserved configural integrity (Study 1: 3/4 profile and full profile poses) or disrupted it while preserving featural information (Study 2: rotations of 160° or 200° and fracturings). There were developmental differences in both speed and in infants' appreciation of information about faces. Older infants took about 60% fewer trials to reach criterion and had more mature patterns of attention (i.e., looks of shorter duration and more shifts of gaze). Whereas infants of both ages recognized the familiar face in a 3/4 pose, the 12‐month‐olds also recognized it in profile and when rotated. Twelve‐month‐olds who were fast processors additionally recognized the fractured faces; otherwise, processing speed was unrelated to the type of information extracted. At 7 months then, infants made use of some configural information in processing faces; at 12 months, they made use of even more of the configural information, along with part‐based or featural information.     

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.     

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.     

Infants' Looking at Possible and Impossible Screen Rotations: The Role of Familiarization

The effects of familiarization and age were examined using Baillargeon's rotating screen paradigm. In Condition A, 4‐month‐olds exposed to 7 180° familiarization trials looked significantly longer at the 180° test events than the 112° test events; there was a familiarity preference. In Condition B, which consisted of 12 instead of 7 180° familiarization trials, the 4‐month‐olds looked significantly longer at the 112° test events than the 180° test events; there was a novelty preference. In Condition C, which was similar to Condition A except that there were 112° familiarization trials, the infants showed a familiarity preference. Thus, 4‐month‐olds experiencing 7 familiarization trials exhibited a familiarity preference, and those experiencing 12 familiarization trials showed a novelty preference. In Condition D, 6‐month‐olds experienced 7 180° familiarization trials; there was no preferential looking to either familiar (180°) test events or novel (112°) test events. Therefore, looking behavior during the test trials was a function of the type of familiarization experience and age and not necessarily an inferred violation of physics.     

The Development of Affect Specificity in Infants' Use of Emotion Cues

This study examined the emergence of affect specificity in infancy. In this study, infants received verbal and facial signals of 2 different, negatively valenced emotions (fear and sadness) as well as neutral affect via a television monitor to determine if they could make qualitative distinctions among emotions of the same valence. Twenty 12‐ to 14‐month‐olds and 20 16‐ to 18‐month‐olds were examined. Results suggested that younger infants showed no evidence of referential specificity, as they responded similarly to both the target and distracter toys, and showed no evidence of affect specificity, showing no difference in play between affect conditions. Older infants, in contrast, showed evidence both of referential and affect specificity. With respect to affect specificity, 16‐ to 18‐month‐olds touched the target toy less in the fear condition than in the sad condition and showed a larger proportion of negative facial expressions in the sad condition versus the fear condition. These findings suggest a developmental emergence after 15 months of age for affect specificity in relating emotional messages to objects.     

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.     

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.     

Young Infants Match Facial and Vocal Emotional Expressions of Other Infants

Research has demonstrated that infants recognize emotional expressions of adults in the first half year of life. We extended this research to a new domain, infant perception of the expressions of other infants. In an intermodal matching procedure, 3.5‐ and 5‐month‐old infants heard a series of infant vocal expressions (positive and negative affect) along with side‐by‐side dynamic videos in which one infant conveyed positive facial affect and another infant conveyed negative facial affect. Results demonstrated that 5‐month‐olds matched the vocal expressions with the affectively congruent facial expressions, whereas 3.5‐month‐olds showed no evidence of matching. These findings indicate that by 5 months of age, infants detect, discriminate, and match the facial and vocal affective displays of other infants. Further, because the facial and vocal expressions were portrayed by different infants and shared no face–voice synchrony, temporal, or intensity patterning, matching was likely based on detection of a more general affective valence common to the face and voice.     

Infants’ Visual Attention to Baby DVDs as a Function of Program Pacing

This study examined the effects of program pacing, defined as the rate of scene and character change per minute, on infants’ visual attention to video presentations. Seventy‐two infants (twenty‐four 6‐month‐olds, twenty‐four 9‐month‐olds, twenty‐four 12‐month‐olds) were exposed to one of two sets of high‐ and low‐paced commercial infant DVDs. Each DVD was approximately 5‐min long, and the order the DVDs were viewed was counterbalanced for pace. Attention was higher during rapidly than slowly paced DVDs, particularly for the 6‐ and 9‐month‐old infants. These results support previous research documenting that attention is initially controlled by exogenous qualities (e.g., rapid pace), but with development and experience becomes more influenced by endogenous factors.     

Language Experience Shapes the Development of the Mutual Exclusivity Bias

Halberda (2003) demonstrated that 17‐month‐old infants, but not 14‐ or 16‐month‐olds, use a strategy known as mutual exclusivity (ME) to identify the meanings of new words. When 17‐month‐olds were presented with a novel word in an intermodal preferential looking task, they preferentially fixated a novel object over an object for which they already had a name. We explored whether the development of this word‐learning strategy is driven by children’s experience of hearing only one name for each referent in their environment by comparing the behavior of infants from monolingual and bilingual homes. Monolingual infants aged 17–22 months showed clear evidence of using an ME strategy, in that they preferentially fixated the novel object when they were asked to “look at the dax.” Bilingual infants of the same age and vocabulary size failed to show a similar pattern of behavior. We suggest that children who are raised with more than one language fail to develop an ME strategy in parallel with monolingual infants because development of the bias is a consequence of the monolingual child’s everyday experiences with words.     

The Development of Gaze Following in a Third‐Party Context

Infants follow the gaze of an individual with whom they are directly interacting by the end of the first year. By 18 months infants are capable of learning novel words in observational (or third‐party) contexts (Floor & Akhtar, 2006). To examine third‐party gaze following in 12‐ and 18‐month‐olds, the parent and experimenter engaged in a conversation while the infant was present. For 8 trials approximately every 30 sec the experimenter would turn her head to the right or left to fixate on a toy placed on either side of the room with the parent following suit. In the first experiment, the parent was seated next to the infant and the experimenter opposite, whereas in the second experiment the positions of the adults were switched. In Experiment 1, 18‐month‐olds but not 12‐month‐olds followed gaze. In Experiment 2, 12‐month‐olds acquired a tendency to follow gaze during the experimental session. These results suggest that an incipient ability to follow third‐party gaze is present by 12 months and that infants acquire a more reliable and general ability to follow the gaze of noninteractive others between 12 and 18 months.     

Follow My Gaze: Face Race and Sex Influence Gaze‐Cued Attention in Infancy

Using the eye gaze of others to direct one's own attention develops during the first year of life and is thought to be an important skill for learning and social communication. However, it is currently unclear whether infants differentially attend to and encode objects cued by the eye gaze of individuals within familiar groups (e.g., own race, more familiar sex) relative to unfamiliar groups (e.g., other race, less familiar sex). During gaze cueing, but prior to the presentation of objects, 10‐month‐olds looked longer to the eyes of own‐race faces relative to 5‐month‐olds and relative to the eyes of other‐race faces. After gaze cueing, two objects were presented alongside the face and at both ages, infants looked longer to the uncued objects for faces from the more familiar‐sex and longer to cued objects for the less familiar‐sex faces. Finally, during the test phase, both 5‐ and 10‐month‐old infants looked longer to uncued objects relative to cued objects but only when the objects were cued by an own‐race and familiar‐sex individual. Results demonstrate that infants use face eye gaze differently when the cue comes from someone within a highly experienced group.     

Infants’ Speed Discrimination: Effects of Different Ratios and Spatial Orientations

This study addressed the question whether 6‐month‐olds’ speed discrimination is ratio dependent and whether an oblique effect (i.e., more accurate discrimination of cardinally as opposed to obliquely oriented objects) affects their speed discrimination skills. Infants were habituated to visual displays showing a ball moving with constant speed and tested with the familiar and a novel speed in the test phase. This ball moved either on a cardinally or obliquely oriented trajectory. Irrespective of orientation, infants looked longer at the novel speed when speeds differed by a ratio of 1:2, whereas they looked indiscriminable at the novel and familiar speeds when they differed by a ratio of 2:3. Our results show remarkable parallels to infants’ ratio‐dependent discrimination behavior in other domains (time, distance, and number), implying that different magnitudes may be processed by the same underlying mechanism. However, our findings also indicate that speed discrimination was not influenced by spatial orientation in a similar way as has been found for other visual perceptual processes.     

Development of Vocal Protests From 3 to 18 Months

Infants often protest the activities of their caregivers, and this particular social interaction may provide an important window on early communication and its development. This study used naturalistic methods to investigate the development of vocal protests. Fifteen mother‐infant dyads at each of 5 ages, from 3 to 18 months, were observed at home. Maternal behaviors of caregiving and prohibiting were tallied from videotapes, as were infants' protests of these behaviors. Maternal caregiving decreased with age, but maternal prohibitions increased. There were no changes over age in the probability of protesting maternal caregiving behavior; however, 12‐month‐olds were more likely to protest prohibitions than 6‐ or 8‐month‐olds. Older infants were also more likely to use intense protests, such as screams, than younger infants. These age‐related changes were mirrored by the differences in prohibitions and protests observed between 8‐month‐olds who could crawl and those who could not. Findings from this study were related to previous research on infant crying as an important part of the prelinguistic communication system.     

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.