Sensory dominance in infants: I. Six-month-old infants' response to auditory-visual compounds.

To investigate sensory dominance in early development, a series of studies was conducted to examine 6-month-old infants' processing of multisensory stimulus compounds. The infants were first habituated with a compound stimulus consisting of a flashing checkerboard and a pulsing sound. To assess attention to aspects of the compound stimulus, the infants received separate test trials where compounds differed in the rate and/or duration at which the visual, the auditory, or both components were presented. One consistent finding was that the infants discriminated changes in the temporal characteristics of the auditory component but not in the visual component. Their responsiveness to the auditory information depended on the number of discriminative cues available during either the habituation or the test phases and on the temporal distinctiveness of the auditory and visual components during the habituation phase. This consistent failure to respond to changes in the visual component led to the conclusion that auditory dominance was operating. This conclusion was reinforced by the finding that the infants failed to discriminate a change in the rate of the visual component even when the intensity of the visual component was increased relative to that of the auditory component, and by the finding that the infants could discriminate temporal changes in the visual component following habituation with just the visual component. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perception of the symmetrical patterning of human gait by infants.

Two experiments tested 3- and 5-month-old infants' sensitivity to properties of point-light displays of human gait. In Experiment 1, infants were tested for discrimination of point-light displays of a walker and a runner, which, although they differed in many ways, were equivalent with regard to the phasing of limb movements. Results revealed that 3-month-old, but not 5-month-old, infants discriminated these displays. In Experiment 2, the symmetrical phase-patterning of the runner display was perturbed by advancing two of its limbs by 25% of the gait cycle. Both 3- and 5-month-old infants discriminated the walker display from this new phase-shifted runner display. These findings suggest that 3-month-old infants respond to the absolute and relative motions within a single limb, whereas 5-month-old infants respond primarily to the relations between limbs and, in particular, to the bilateral symmetry between the limbs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Long-term recognition memory for faces assessed by visual paired comparison in 3- and 6-month-old infants.

It has been argued that operant conditioning is the only type of long-term memory present in infants prior to 6 months of age. In this study, memory for faces was investigated in 3- and 6-month-old infants with a visual paired-comparison task. In Experiment 1, infants were habituated to a face presented in different poses; recognition was assessed after a 2-min or a 24-hr retention interval. The 6-month-old infants and the male but not the female 3-month-old infants exhibited novelty preferences. A 2nd experiment showed that 3-month-old female infants were delayed relative to male infants in their face-processing ability rather than in their memory capacity. The results of Experiment 3 demonstrated in 3-month-olds an electrophysiological correlate of delayed recognition memory. These findings are discussed in the context of the neural systems thought to be involved in visual recognition memory (but not in procedural memory), namely the limbic system. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sensory dominance in infants: II. Ten-month-old infants' response to auditory-visual compounds.

A series of studies was conducted with 10-month-old infants in which their response to temporally modulated auditory-visual compounds was examined. The general procedure consisted of first habituating the infants to a compound stimulus (consisting of a flashing checkerboard and a pulsing sound) and then testing their response to it by presenting a series of trials where either one or two temporal attributes of the visual, the auditory, or of both components were changed. When the auditory and visual components were temporally identical, during the habituation phase, the infants only encoded the temporal attributes of the auditory component. When the two components were temporally distinct, or when they were identical but when multiple discriminative cues were available, the infants encoded the temporal aspects of both the auditory and the visual components. When the information context was made more complex, the infants' performance deteriorated, but when the salience of the visual component was increased the infants' performance improved. In sum, although the auditory modality can dominate the visual modality at 10 months of age, the visual modality can process temporal information when the temporal relationship of the information in the two modalities is distinct. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Infants' association of linguistic labels with causal actions.

Six experiments examined infants' ability to associate nonsense words with 2 causal actions: pushing and pulling. Although Experiment 1 found that 14-month-olds failed to form word-action associations, 18-month-olds in Experiment 2 provided reliable evidence of doing so. Additional experiments explore why 14-month-olds may not have formed such an association. Experiment 3 examined 14-month-old's ability to discriminate a change in either the action or the label when the other element was held constant. Infants discriminated the change in label but not the change in action. When the language labels were replaced with music (Experiments 4–6), 14-month-old infants responded in terms of and discriminated between pushing and pulling. These results, in comparison with those from Experiments 1 and 3, suggest that for 14-month-olds, attempting to associate labels with actions may interfere with their discrimination of similar actions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The sound of darkness: Why do auditory cues aid infants' search for objects hidden by darkness but not by visible occluders?

In manual search tasks designed to assess infants' knowledge of the object concept, why does search for objects hidden by darkness precede search for objects hidden by visible occluders by several months? A graded representations account explains this décalage by proposing that the conflicting visual input from occluders directly competes with object representations, whereas darkness merely weakens representations. This study tests the prediction that representations of objects hidden by darkness are strong enough for infants to bind auditory cues to them and support search, whereas representations of objects hidden by occluders are not. Six-and-half-month-olds were presented with audible or silent objects that remained visible, became hidden by darkness, or became hidden by a visible occluder. Search required engaging in the same means-end action in all conditions. As predicted, auditory cues increased search when objects were hidden by darkness but not when they were hidden by a visible occluder. Results are discussed in the context of different facets of object concept development highlighted by graded representations perspectives and core knowledge perspectives and in relation to other work on multimodal object representations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Textons, visual pop-out effects, and object recognition in infancy.

Five experiments were conducted to determine whether primitive perceptual features, or textons, which B. Julesz (1984) identified in studies of texture segregation with adults, also affect object recognition early in development. Three-month-old infants discriminated Ts and Ls composed of overlapping line segments from +s but not from each other in a delayed-recognition test after 24 hrs; however, Ts and Ls were discriminated from each other after only 1 hr. In a priming paradigm, Ts, Ls, and +s were discriminated from one another after 2 wks. In succeeding experiments, infants exhibited adultlike visual pop-out effects in both delayed recognition and priming paradigms, detecting an L in the midst of 6 +s and vice versa; these effects were symmetrical. The pop-out effects apparently resulted from parallel search: Infants failed to detect 3 Ls among 4 +s. Clearly, some of the same primitive units that have been identified as the building blocks of adult visual perception underlie object recognition early in infancy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Infant discrimination of faces in naturalistic events: Actions are more salient than faces.

Despite the fact that faces are typically seen in the context of dynamic events, there is little research on infants' perception of moving faces. L. E. Bahrick, L. J. Gogate, and I. Ruiz (2002) demonstrated that 5-month-old infants discriminate and remember repetitive actions but not the faces of the women performing the actions. The present research tested an attentional salience explanation for these findings: that dynamic faces are discriminable to infants, but more salient actions compete for attention. Results demonstrated that 5-month-old infants discriminated faces in the context of actions when they had longer familiarization time (Experiment 1) and following habituation to a single person performing 3 different activities (Experiment 2). Further, 7-month-old infants who have had more experience with social events also discriminated faces in the context of actions. Overall, however, discrimination of actions was more robust and occurred earlier in processing time than discrimination of dynamic faces. These findings support an attentional salience hypothesis and indicate that faces are not special in the context of actions in early infancy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fearful faces but not fearful eyes alone delay attention disengagement in 7-month-old infants.

Adult-like attentional biases toward fearful faces can be observed in 7-month-old infants. It is possible, however, that infants merely allocate attention to simple features such as enlarged fearful eyes. In the present study, 7-month-old infants (n = 15) were first shown individual emotional faces to determine their visual scanning patterns of the expressions. Second, an overlap task was used to examine the latency of attention disengagement from centrally presented faces. In both tasks, the stimuli were fearful, happy, and neutral facial expressions, and a neutral face with fearful eyes. Eye-tracking data from the first task showed that infants scanned the eyes more than other regions of the face; however, there were no differences in scanning patterns across expressions. In the overlap task, infants were slower in disengaging attention from fearful as compared to happy and neutral faces and also to neutral faces with fearful eyes. Together, these results provide evidence that threat-related stimuli tend to hold attention preferentially in 7-month-old infants and that the effect does not reflect a simple response to differentially salient eyes in fearful faces. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Infants' localization of sounds along the horizontal axis: Estimates of minimum audible angle.

Localization acuity was examined by determining the smallest sound shift off midline and along the horizontal axis that infants could reliably discriminate (i.e., minimum audible angle). Infants 6, 9, 12, 15, and 18 months of age were seated in a dark room facing an array of nine loudspeakers positioned along the horizontal axis and at ear level. One loudspeaker was positioned at midline, 0°, and four others each were positioned to the right and left of 0°. A two-alternative forced-choice procedure was used in conjunction with a method of constant stimuli. A sequence of white-noise bursts was presented initially at 0° and was then shifted horizontally (right or left of 0°). The sequence continued to be presented until the infant made a directional head or eye movement, or both. Correct responses were visually reinforced. With increasing age, infants demonstrated a finer partitioning of auditory space along the horizontal axis. At 6 months, only a location shift of at least 12° off midline was reliably discriminated, whereas, by 18 months, infants reliably discriminated a shift of only 4°. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of an abstract category representation for the spatial relation between in 6- to 10-month-old infants.

Nine experiments examined the formation of an abstract category representation for the spatial relation between by 6- to 10-month-old infants. The experiments determined that 9- to 10-month-olds, but not 6 to 7-month-olds, could form an abstract category representation for between when performing in an object-variation version of the between categorization task. The results also demonstrated that 6- to 7-month-olds could form category representations for between in the object-variation version of the between categorization task but that such representations were specific to the particular objects presented. The evidence confirms that representations for different spatial relations emerge at different points during development, and suggests that each representation undergoes its own period of development from concrete to abstract. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Infants of Chronically Depressed Mothers Learn in Response to Male, But Not Female, Infant-Directed Speech.

Previous research using a conditioned-attention paradigm demonstrated that 4-month-old infants of depressed mothers (a) failed to acquire associations when a segment of their mothers' infant-directed (ID) speech signaled the presentation of a smiling face but (b) did acquire associations when a segment of an unfamiliar nondepressed mother's ID speech signaled the face (P. S. Kaplan, J. -A. Bachorowski, M. J. Smoski, & W. J. Hudenko, 2002). In the present study, 5- to 13-month-old infants of depressed mothers failed to acquire associations when either their own mothers' (Experiment 1) or an unfamiliar nondepressed mother's (Experiments 1 and 2) ID speech signaled a face. However, these infants acquired associations when a segment of an unfamiliar nondepressed father's ID speech served as the signal (Experiment 2). One possible explanation of these results is that infants of depressed mothers selectively "tune out" ID speech from their mothers and from other, nondepressed, women. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Multimodal Events and Moving Locations: Eye Movements of Adults and 6-Month-Olds Reveal Dynamic Spatial Indexing.

The ability to keep track of locations in a dynamic, multimodal environment is crucial for successful interactions with other people and objects. The authors investigated the existence and flexibility of spatial indexing in adults and 6-month-old infants by adapting an eye-tracking paradigm from D. C. Richardson and M. J. Spivey (2000). Multimodal events were presented in specific locations, and eye movements were measured when the auditory portion of the stimulus was presented without its visual counterpart. Experiment 1 showed that adults spatially index auditory information even when the original associated locations move. Experiments 2 and 3 showed that infants are capable of both binding multimodal events to locations and tracking those locations when they move. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Set size, novelty, and visual pop-out in infancy.

The effects of set size and novelty on visual pop-out in 6-month-old infants was assessed in a perceptual-identification (memory reactivation) paradigm in which infants, trained and tested in their own homes, viewed a mobile containing a unique novel or familiar object amidst different numbers of familiar or novel distractors, respectively. Unique objects of both types popped out at all set sizes except the largest, where there was modest evidence that familiar distractors speeded processing (Experiment 1). When the proportion of familiar targets in a display of intermediate set size was increased, however, infants no longer detected the familiar target (Experiment 2). These findings offer additional support for the proposition that visual pop-out in infants and adults is the same phenomenon. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Gender differences in emotional expressivity and self-regulation during early infancy.

Eighty-one 6-month-old infants and their mothers were videotaped in E. Z. Tronick's face-to-face still-face paradigm to evaluate gender differences in infant and maternal emotional expressivity and regulation. Male infants had greater difficulty than female infants in maintaining affective regulation during each episode, including the still face. Mother–son dyads had higher synchrony scores than mother–daughter dyads but took longer in repairing interactive errors. In addition, maternal affect, matching, rate of change between matching and mismatching states, and synchrony in the play preceding the still face differentially mediated male and female infants' responses to the still face and reunion play. The developmental implications of these gender differences are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learning to form a spatial category of tight-fit relations: How experience with a label can give a boost.

Two experiments explored the ability of 18-month-old infants to form an abstract categorical representation of tight-fit spatial relations in a visual habituation task. In Experiment 1, infants formed an abstract spatial category when hearing a familiar word (tight) during habituation but not when viewing the events in silence or when hearing a novel word. In Experiment 2, infants were given experience viewing and producing tight-fit relations while an experimenter labeled them with a novel word. Following this experience, infants formed the tight-fit spatial category in the visual habituation task, particularly when hearing the novel word again during habituation. Results suggest that even brief experience with a label and tight-fit relations can aid infants in forming an abstract categorical representation of tight-fit relations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learning and discrimination of audiovisual events in human infants: The hierarchical relation between intersensory temporal synchrony and rhythmic pattern cues.

This study examined 4- to 10-month-old infants' perception of audio-visual (A-V) temporal synchrony cues in the presence or absence of rhythmic pattern cues. Experiment 1 established that infants of all ages could successfully discriminate between two different audiovisual rhythmic events. Experiment 2 showed that only 10-month-old infants detected a desynchronization of the auditory and visual components of a rhythmical event. Experiment 3 showed that 4- to 8-month-old infants could detect A-V desynchronization but only when the audiovisual event was nonrhythmic. These results show that initially in development infants attend to the overall temporal structure of rhythmic audiovisual events but that later in development they become capable of perceiving the embedded intersensory temporal synchrony relations as well. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Newborns discriminate schematic faces from scrambled faces.

Examined newborn attention to, and discrimination of, facelike patterns in 3 experiments employing 35 one- to three-day-old infants. Differential eye tracking and head turning to three moving stimuli (a schematic face, a scrambled face, and a luminance-matched blank) were measured in 2 of the 3 experiments. The Ss turned their eyes and heads farther to follow patterned stimuli, containing facelike features, than to a luminance-matched blank, but they did not turn farther to a stimulus with the features arranged in a facelike manner compared to features scrambled. A 3rd experiment tested Ss' ability to discriminate between the facelike and scrambled face patterns. Using an infant-controlled procedure, Ss showed similar initial fixation times and similar numbers of trials to reach a 60% response decrement criterion to both patterned stimuli. Following habituation, novelty responding indicated that the Ss discriminated between the schematic face and the scrambled face patterns. Although Ss did not show a preference for a facelike stimulus compared to a features-scrambled pattern in the present experiments, they could discriminate the two patterns based on the internal arrangement of the facial features. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Infants' perception of object unity in translating and rotating displays

In 3 experiments, the authors examined the sensitivity of infants to the unity of a partly occluded moving rod undergoing translation, rotation, or oscillation. Four-month-old infants were sensitive to the unity of the partly occluded rod when it translated, but not when it rotated, behind an occluder. Six-month-old infants perceived the rotating rod as continuing behind the occluder, but they did not perceive the unity of a rod that oscillated back and forth behind the occluder. Finally, 6-month-old infants showed an ambiguous response to a rotating rod when the shape of the occluder was changed from rectangular to round. These findings suggest that all types of common motion are not equivalent for specifying infants' perceptions of occluded objects. Additional factors should be considered that take into account the information specified by different types of motion and by different conditions at the intersection of the occluder and the object.