Individual Differences in Infant Oculomotor Behavior During the Viewing of Complex Naturalistic Scenes

Little research hitherto has examined how individual differences in attention, as assessed using standard experimental paradigms, relate to individual differences in how attention is spontaneously allocated in more naturalistic contexts. Here, we analyzed the time intervals between refoveating eye movements (fixation durations) while typically developing 11‐month‐old infants viewed a 90‐min battery ranging from complex dynamic to noncomplex static materials. The same infants also completed experimental assessments of cognitive control, psychomotor reaction times (RT), processing speed (indexed via peak look during habituation), and arousal (indexed via tonic pupil size). High test–retest reliability was found for fixation duration, across testing sessions and across types of viewing material. Increased cognitive control and increased arousal were associated with reduced variability in fixation duration. For fixations to dynamic stimuli, in which a large proportion of saccades may be exogenously cued, we found that psychomotor RT measures were most predictive of mean fixation duration; for fixations to static stimuli, in contrast, in which there is less exogenous attentional capture, we found that psychomotor RT did not predict performance, but that measures of cognitive control and arousal did. The implications of these findings for understanding the development of attentional control in naturalistic settings are discussed.     

Typical and Atypical Development of Visual Attention in 3‐ to 9‐Month‐Old Infants

The interactions between attention and stimulus encoding in infancy were examined using heart rate (HR) and visual habituation measures. At 3, 6, and 9 months of age, infants (N = 119) were habituated to an adult face; longest look (LL) duration was measured as an indicator of encoding speed. Three groups were formed based on LL change from 3 to 9 months: Large Decrease, Small Decrease, and Increase. Using concurrent electrocardiograph recordings, attention was measured through the percentage of looking time in orienting, sustained attention, and attention termination. We partially replicated previous findings regarding developmental patterns of attention in these three groups, notably that these patterns were different for the Increase group. Looks away from the stimulus were also assessed in each attentional phase and, as predicted, HR acceleration phases showed less visual engagement than HR deceleration phases. We also found anomalous behavior for the LL Increase group. In general, this small but distinct group showed similarities at 3 months to the presumably more mature behavior of typical 9 month olds, but by 9 months, they behaved more like typical 3 month olds regarding some, but not all, cognitive measures. These results are discussed in the context of the development of endogenous attention.     

The Effect of Maternal Mirroring Behavior on Infants’ Early Social Bidding During the Still‐Face Task

Maternal mirroring behavior, which is a particularly salient form of maternal responsiveness, was investigated as a predictor of infants’ social bids in the Still‐Face Task. Mother–infant dyads engaged in the Still‐Face Task when infants were 5 months, on the cusp of the active emergence of social bidding during the still‐face phase of the task. Maternal mirroring of infants’ behavior during the interactive phases of the task was a primary predictor of infants’ social bids in the still‐face phase. When infants were divided into those who experienced higher maternal mirroring (maternal mirroring above the mean of the sample) and infants who experienced lower maternal mirroring (maternal mirroring at or below the mean), infants with higher maternal mirroring showed increases in nondistress vocalizations during the still‐face phase, indicative of social bidding, whereas the infants with lower maternal mirroring showed little change in nondistress vocalizations across the phases. Maternal mirroring allows infants to readily notice the relation between their own behaviors and those of their mothers, which may enhance infants’ early understanding that they can be active agents in instigating social interactions, as demonstrated by social bidding.     

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.     

Temporal Sequence of Global‐Local Processing in 3‐Month‐Old Infants

In 3 experiments, the temporal processing sequence of local and global visual properties was investigated with 3‐month‐old infants. Across the experiments, a global pattern was discriminated under conditions of less familiarization than was necessary for local elements to be discriminated, thus indicating a global precedence in the sequence of visual processing at 3 months of age. Patterns of discrimination were also observed to vary as a function of individual differences in infants' look duration. Furthermore, the pattern of novelty and familiarity preferences for short‐looking infants varied in complex ways as a function of familiarization time: Preferences for novel global properties were supplanted by familiarity preferences at the point in familiarization at which infants first became sensitive to local properties.     

Individual Differences in Infants' Recognition of Briefly Presented Visual Stimuli

Infants' recognition memory has been shown to be related to individual differences in look duration and level of heart period variability. This study examined the effect of individual differences in these 2 measures on infants' recognition of briefly presented visual stimuli using a paired‐comparison recognition‐memory paradigm. A sample of 35 full‐term infants was studied longitudinally at 14, 20, and 26 weeks of age. Recognition memory for briefly presented stimuli was tested in 6 experimental conditions, with delays corresponding to different heart‐rate‐defined phases of attention. The 20‐and 26‐week‐old infants, and infants with high levels of heart period variability, generally showed more evidence of recognition memory for briefly presented visual stimuli. Greater evidence of recognition memory was observed when stimuli were presented during sustained attention. Infants with more mature baseline physiological responses show greater evidence of recognition memory, and stimulus and procedural factors may be more important for the study of individual differences in infant visual attention than has previously been suggested.     

Brain Electrical Activity Associated With Cognitive Processing During a Looking Version of the A‐Not‐B Task

This work was designed to investigate individual differences in brain electrical activity during a looking version of the A‐not‐B task. It was proposed that this spatial task required the cognitive skills of working memory and inhibitory control, each associated with frontal lobe function. Electroencephalograms (EEGs) were recorded from 54 8‐month‐old infants during baseline and task. Only high performers on the looking task exhibited increases in 6‐ to 9‐Hz EEG power from baseline to task. These task‐related changes were evident at frontal and posterior scalp locations. High performers on the looking task exhibited lower EEG coherence values at right hemisphere frontal locations relative to the low performers. These lower coherence values were evident during baseline and task. All infants showed increased frontal‐parietal coherence during the spatial working memory task relative to baseline values. These data confirm previous cognitive neuroscience work associating frontal lobe function with cognitive performance levels during infancy.     

Infants' Response to Maternal Mirroring in the Still Face and Replay Tasks

Infants' response to maternal mirroring was investigated in 4‐month‐old infants. Mother–infant dyads participated in the still face and replay tasks. Infants were grouped by those whose mothers did and did not mirror their behavior in the interactive phases of the tasks. In the still face task, infants with maternal mirroring showed more attention, smiling, and positive vocalizations across the phases, although both groups of infants demonstrated the still‐face effect with attention and smiling. Infants' social bidding to the mother during the still‐face phase correlated with mothers' mirroring behavior. In the replay task, infants with maternal mirroring demonstrated carryover effects with smiling; infants without maternal mirroring showed no awareness of change in their mothers' behavior. In both the still face and replay tasks, infants with maternal mirroring were more engaged with their mothers. Results suggest that maternal mirroring of infants' behavior affects infants' detection of, and response to, reciprocal interaction.     

The Role of Dyadic Coordination in Organizing Visual Attention in 5‐Month‐Old Infants

In human infants, the ability to share attention with others is facilitated by increases in attentional selectivity and focus. Differences in early attention have been associated with socio‐cognitive outcomes including language, yet the social mechanisms of attention organization in early infancy have only recently been considered. Here, we examined how social coordination between 5‐month‐old infants and caregivers relate to differences in infant attention, including looking preferences, span, and reactivity to caregivers’ social cues. Using a naturalistic play paradigm, we found that 5‐month‐olds who received a high ratio of sensitive (jointly focused) contingent responses showed strong preferences for objects with which their caregivers were manually engaged. In contrast, infants whose caregivers exhibited high ratios of redirection (attempts to shift focus) showed no preferences for caregivers’ held objects. Such differences have implications for recent models of cognitive development, which rely on early looking preferences for adults’ manually engaged objects as a pathway toward joint attention and word learning. Further, sensitivity and redirectiveness predicted infant attention even in reaction to caregiver responses that were non‐referential (neither sensitive nor redirective). In response to non‐referentials, infants of highly sensitive caregivers oriented less frequently than infants of highly redirective caregivers, who showed increased distractibility. Our results suggest that specific dyadic exchanges predict infant attention differences toward broader social cues, which may have consequences for social‐cognitive outcomes.     

Neural Correlates of Individual Differences in Infant Visual Attention and Recognition Memory

Past studies have identified individual differences in infant visual attention based upon peak look duration during initial exposure to a stimulus. Colombo and colleagues found that infants that demonstrate brief visual fixations (i.e., short lookers) during familiarization are more likely to demonstrate evidence of recognition memory during subsequent stimulus exposure than infants that demonstrate long visual fixations (i.e., long lookers). This study utilized event‐related potentials (ERPs) to examine possible neural mechanisms associated with individual differences in visual attention and recognition memory for 6‐ and 7.5‐month‐old infants. Short‐ and long‐looking infants viewed images of familiar and novel objects during ERP testing. There was a stimulus type by looker type interaction at temporal and frontal electrodes on the late slow wave (LSW). Short lookers demonstrated an LSW that was significantly greater in amplitude in response to novel stimulus presentations. No significant differences in LSW amplitude were found based on stimulus type for long lookers. These results indicate deeper processing and recognition memory of the familiar stimulus for short lookers.     

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.     

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 Still‐Face Effect: Methodological Issues and New Applications

Over the last 25 years, the seemingly simple still‐face phenomenon has elicited a tremendous amount of empirical and theoretical work. Adamson and Frick (2003/this issue) provide a comprehensive review and in‐depth analysis of this large body of research. In our commentary, we focus on 3 major points. First, we described several methods to define operationally the still‐face effect. Second, we noted the important role of adult touch in the still‐face procedure, and that the effect can be reproduced without adult touch, by live, televised and “virtual” adult faces–‐making it a true “still‐face” effect. Third, we emphasized a major methodological strength of the still‐face procedure: the use of multiple response measures. By measuring both infant visual attention and affect responses, adaptations of the still‐face procedure provide infant researchers with a powerful general method for studying the development of infant social competence.     

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.     

Behavior of Mothers and Infants With and Without Down Syndrome During the Still‐Face Procedure

There has been limited study of how the constitutional characteristics of infants with Down syndrome (DS) influence the patterning of their relations with caregivers. To assess natural and perturbed interactions between infants with DS and their mothers, we tested ten 6‐month‐old infants with DS and 20 typically developing (TD) 4‐month‐old of similar mental age. Participants were videotaped with their mothers in a natural face‐to‐face interaction, a brief period when the mothers adopted a still‐face, and a subsequent reengagement phase. There was little to distinguish the infants in the initial phase of natural interaction, but the mothers of infants with DS were more likely to show assertive warmth, and unlike in the case of mothers of TD infants, high maternal directiveness tended to be associated with lower levels of infant looking and lack of fussing. During the still‐face episode, infants of both groups showed reduced looking and smiling, although infants with DS tended to show lower levels of fussing and fewer in this group showed fussing in the reengagement phase. Therefore DS infants were somewhat similar to TD infants of comparable mental age in being responsive to the still‐face procedure, but showed indications of group differences in intense emotional reactivity.     

Infants’ response to a mobile phone modified still‐face paradigm: Links to maternal behaviors and beliefs regarding technoference

Interruptions to parent–child interactions due to technology, or “technoference,” have been correlated with a host of negative child developmental outcomes. Yet, the influence of technoference on parent–infant interactions and infant behaviors has received less attention and more experimental work is warranted. For this study, parent–infant dyads (n = 227) completed a modified still‐face paradigm (SFP) using a mobile phone during the still‐face phase. Infant responses were coded for positive and negative affect, object and parent orientation, self‐comforting, and escape behaviors during the task. Results showed a robust still‐face effect, with infants displaying increased negative affect, decreased positive affect, increased self‐comforting, object orientation, and escape behaviors during the “still‐face” or phone distracted phase of the paradigm and frequently failing to return to baseline during the reunion phase. Older infants (older than 9 months) likewise demonstrated higher levels of negative affect across all three phases of the paradigm relative to younger infants (less than 9 months). Parent reports of technoference behavior were related to increased object orientation for younger infants. Parental technoference behaviors were also linked to more escape behaviors for younger infants and decreased object orientation in older infants during the still‐face portion of the SFP. Higher levels of technoference also appear to attenuate the negative emotional response of infants during still face. Results are discussed in relation to infants’ increasing exposure to digital technology in the context of early relationships.     

Effects of Maternal Responsiveness on Infant Responsiveness and Behavior in the Still‐Face Task

The effects of maternal responsiveness on infant responsiveness and behavior in the Still‐Face Task were longitudinally examined through infants' first 3 months. Maternal vocal responsiveness and infant vocal and smiling responsiveness significantly increased when infants were 2 months of age. Mothers showed continuity of individual differences in vocal responsiveness from the infants' newborn period. Maternal responsiveness predicted infant responsiveness within and across sessions. Compared with infants with low‐responsive mothers, infants with high‐responsive mothers were more attentive and affectively engaged during the Still‐Face Task from 1 month of age. Infants with high‐responsive mothers discriminated between the task phases with their smiling at 1 month, a month before infants with low‐responsive mothers did so. Infants in both groups discriminated between the phases with their attention and nondistress vocalizations throughout their first 3 months. Results suggest that maternal responsiveness influences infant responsiveness and facilitates infants' engagement and expectations for social interaction.     

Contributions of Look Duration and Gaze Shift Patterns to Infants’ Novelty Preferences

Data from 72 infants, tested using a serial paired‐comparison paradigm, were analyzed to better understand infant novelty preferences. Infants between the ages of 15 and 26 weeks were tested in three studies with familiar stimuli displayed adjacent to novel stimuli on each trial. Differences in look duration, look number, and gaze shifts directed at novel versus familiar stimuli were assessed to measure their contributions to group and individual novelty preferences. Infants produced longer looks for novel stimuli in all three studies, and stimulus differences in look duration accounted for more than 50% of the variability in individual novelty preferences. Infants that produced more looks to novel rather than familiar stimuli did not produce overall novelty preferences unless they also looked longer at novel stimuli. Gaze shift patterns did not predict individual novelty preferences, and novel stimuli did not determine where infants looked. The infants’ visual exploration was constrained by memories for the direction of the previous look as well as by the attention‐holding features of novel stimuli.     

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.     

A Comparison of Visual Familiarization and Object‐Examining Measures of Categorization in 9‐Month‐Old Infants

Three studies were conducted to determine whether differential patterns of categorization observed in studies using visual familiarization and object‐examining measures hold up as procedural confounds are eliminated. In Experiment 1, we attempted as direct a comparison as possible between visual and object‐examining measures of categorization. Consistent with previous reports, 9‐month‐old infants distinguished a basic‐level contrast (dog–horse) in the visual task, but not in the examining task. Experiment 2 was designed to reduce levels of nonexploratory activity in an examining task; 9‐month‐olds again failed to distinguish categories of dogs and horses. In Experiment 3, we adopted a paired‐comparison test format in the object‐examining task. Infants did display a novel category preference under paired testing conditions. The results suggest that the different patterns of categorization often seen in looking and touching tasks are a reflection, not of different categorization processes, but of the differential sensitivity of the tasks.