Speech Perception by 6‐to 8‐Month‐Olds in the Presence of Distracting Sounds

The role of selective attention in infant phonetic perception was examined using a distraction masker paradigm. We compared perception of /bu/ versus /gu/ in 6‐ to 8‐month‐olds using a visual fixation procedure. Infants were habituated to multiple natural productions of 1 syllable type and then presented 4 test trials (old‐new‐old‐new). Perception of the new syllable (indexed as novelty preference) was compared across 3 groups: habituated and tested on syllables in quiet (Group 1), habituated and tested on syllables mixed with a nonspeech signal (Group 2), and habituated with syllables mixed with a non‐speech signal and tested on syllables in quiet (Group 3). In Groups 2 and 3, each syllable was mixed with a segment spliced from a recording of bird and cricket songs. This nonspeech signal has no overlapping frequencies with the syllable; it is not expected to alter the sensory structure or perceptual coherence of the syllable. Perception was negatively affected by the presence of the auditory distracter during habituation; individual performance levels also varied more in these groups. The findings show that perceiving speech in the presence of irrelevant sounds poses a cognitive challenge for young infants. We conclude that selective attention is an important skill that supports speech perception in infants; the significance of this skill for language learning during infancy deserves investigation.     

Infant‐Directed Speech Is Modulated by Infant Feedback

When mothers engage in infant‐directed (ID) speech, their voices change in a number of characteristic ways, including adopting a higher overall pitch. Studies have examined these acoustical cues and have tested infants' preferences for ID speech. However, little is known about how these cues change with maternal sensitivity to infant feedback in the context of interaction. In this study, each mother watched her infant (located in an adjacent sound booth) on a video screen and talked to him or her through a microphone. The mother believed that her infant could hear her voice and she attempted to make her infant happy through her vocalizations. In reality, the infant could not hear her voice. The mother's ID speech was analyzed in real time for changes in mean pitch. For half of the infant–mother dyads an experimenter surreptitiously positively engaged the infant when the voice analysis revealed a rise in pitch, thereby producing positive reinforcement to the mother for natural higher pitched ID speech. The other half were reinforced for lower pitched ID speech. Mothers raised their pitch significantly more in the former than the latter condition, illustrating that the pitch of ID speech is dynamically affected by feedback from the infant.     

Eighteen‐Month‐Olds,but not 14‐Month‐Olds,Use Social Context to Bind Action Sequences

We demonstrate that 18‐month‐olds, but not 14‐month‐olds, can anticipate others' actions based on an interpretation of shared goals that bind together individual actions into a collaborative sequence. After viewing a sequence of actions performed by two people who socially interact, 18‐month‐olds bound together the socially engaged actors' actions such that they later expected the actors to share the same final goal. Eighteen‐month‐olds who saw nonsocially engaged actors did not have this expectation and neither did 14‐month‐olds when viewing either socially or nonsocially engaged actors. The results are discussed in light of the possibility that experience in collaborations could be necessary for understanding collaboration from a third‐person perspective.     

Retrieval Protracts Deferred Imitation by 6‐Month‐Olds

Past research using a deferred imitation task has shown that 6‐month‐olds remember a 3‐part action sequence for only 1 day. The concept of a time window suggests that there is a limited period within which additional information can be integrated with a prior memory. Its width tracks the forgetting function of the memory. This study asked if retrieving the memory of the modeled actions at the end of the time window protracts its retention, if the type of retrieval (active or passive) differentially influences retention, and if the retrieval delay influences its specificity. In Experiment 1, 6‐month‐olds either imitated the modeled actions (active retrieval group) or merely watched them modeled again (passive retrieval group) 1 day after the original demonstration. Both groups showed deferred imitation after 10 days. In Experiment 2, 6‐month‐olds who repeatedly retrieved the memory at or near the end of the time window deferred imitation for 2.5 months. In Experiment 3,6‐month‐olds spontaneously generalized imitation late in the time window after 1 prior retrieval, whether it was active or passive. These studies reveal that the retention benefit of multiple retrievals late in the time window is huge. Because most retrievals are undoubtedly latent, the contribution of repeated events to the growth of the knowledge base early in infancy has been greatly underestimated.     

Successful Word Recognition by 10‐Month‐Olds Given Continuous Speech Both at Initial Exposure and Test

Most words that infants hear occur within fluent speech. To compile a vocabulary, infants therefore need to segment words from speech contexts. This study is the first to investigate whether infants (here: 10‐month‐olds) can recognize words when both initial exposure and test presentation are in continuous speech. Electrophysiological evidence attests that this indeed occurs: An increased extended negativity (word recognition effect) appears for familiarized target words relative to control words. This response proved constant at the individual level: Only infants who showed this negativity at test had shown such a response, within six repetitions after first occurrence, during familiarization.     

Sensitivity to Social Contingency and Positive Emotion in 2‐Month‐Olds

This study was aimed at sorting out conflicting results in the literature concerning 2‐month‐olds' sensitivity to interpersonal contingency, and investigated the potential role of infants' positive emotion in contingency detection. Infants were randomly assigned to an experimental group (EG) that was presented an uninterrupted live–replay–live sequence of three 30‐sec episodes of their mothers' communicative behavior using a double video TV paradigm, or to a control group (CG) that was presented an uninterrupted 90 sec of contingent maternal interactions. Infants of the EG grimaced more than infants of the CG only during the 2nd period of social exchange (replay vs. 2nd live period), but there was an increase of grimacing and a reduction in gazing during the 3rd period of televised interactions in infants of the CG. Each group was split into 2 subgroups a posteriori according to the presence or absence of smiling during the 1st contingent episode. Smiling infants of the EG reacted more negatively during the 2nd interaction period compared to other subgroups. These findings support the view that sensitivity, not fatigue or loss of interest to maternal stimulation, accounts for 2‐month‐olds' expressive changes during noncontingent maternal interactions; fatigue or loss of interest better explains the decline in attention and the increase of negative expressiveness during the last period of contingent interaction. The findings also suggest that the emotional climate of dyadic exchanges could be a contributing factor to infants' ability to detect the relations between their own actions and those of their social partners.     

Bias for Vocalic Over Consonantal Information in 6‐Month‐Olds

Human languages rely on the ability to learn and produce an indefinite number of words by combining consonants and vowels in a lawful manner. The categorization of speech representations into consonants and vowels is evidenced by the tendency of adult speakers, attested in many languages, to use consonants and vowels for different tasks. Consonants are favored in lexical tasks, while vowels are favored to learn structural regularities. Recent results suggest that this specialization is already observable at 12 months of age in Italian participants. Here, we investigated the representations of younger infants. In a series of anticipatory looking experiments, we showed that Italian 6‐month‐olds rely more on vowels than on consonants when learning the predictions made by individual words (Experiment 1) and are better at generalizing a structure when it is implemented over vowels than when it is implemented over consonants (Experiments 2 and 3). Until 6 months of age, infants thus show a general vocalic bias, which contrasts with the specialization previously observed at 12 months. These results suggest the format of speech representations changes during the second semester of life.     

Abstract Rule Learning for Visual Sequences in 8‐ and 11‐Month‐Olds

The experiments reported here investigated the development of a fundamental component of cognition: to recognize and generalize abstract relations. Infants were presented with simple rule‐governed patterned sequences of visual shapes (ABB, AAB, and ABA) that could be discriminated from differences in the position of the repeated element (late, early, or nonadjacent, respectively). Eight‐month‐olds were found to distinguish patterns on the basis of the repetition, but appeared insensitive to its position in the sequence; 11‐month‐olds distinguished patterns over the position of the repetition, but appeared insensitive to the nonadjacent repetition. These results suggest that abstract pattern detection may develop incrementally in a process of constructing complex relations from more primitive components.     

Experimenter Affective Expression and Gaze Following in 7‐Month‐Olds

The study of gaze following in infants younger than 12 months of age has emphasized the effects of gesture, type of target, and its position or placement. This experiment extends this literature by examining the effects of adults' affective expression on 7‐month‐olds' gaze following. The effects of 3 affective expressions—happy, sad, and neutral—on 7‐month‐olds' frequency of gaze following were examined. The results indicated that infants more frequently followed the gaze of an adult posing a neutral expression than that of an adult posing either a happy or a sad expression. The infants also looked proportionately longer toward the indicated target when the adult's expression was neutral. The results are interpreted in terms of infants' flexibility of attention.     

Limits on Composition of Conceptual Operations in 9‐Month‐Olds

Complex systems are often built from a relatively small set of basic features or operations that can be combined in myriad ways. We investigated the developmental origins of this compositional architecture in 9‐month‐old infants, extending recent work that demonstrated rudimentary compositional abilities in preschoolers. Infants viewed two separate object‐occlusion events that depicted a single‐feature‐change operation. They were then tested with a combined operation to determine whether they expected the outcome of the two feature changes, even though this combination was unfamiliar. In contrast to preschoolers, infants did not appear to predictively compose these simple feature‐change operations. A second experiment demonstrated the ability of infants to track two operations when not combined. The failure to compose basic operations is consistent with limitations on object tracking and early numerical cognition (Feigenson & Yamaguchi, Infancy, 2009, 14, 244). We suggest that these results can be unified via a general principle: Infants have difficulty with multiple updates to a representation of an unobservable.     

Maternal Depression and the Ability to Facilitate Joint Attention With 18‐Month‐Olds

Maternal depression has been associated with the mother‐child dyad's ability to engage in joint attention. This study of 69 depressed and 63 control mothers and their 18‐month‐olds addresses how aspects of maternal psychopathology are related to joint attention during a snack interaction. Although nondepressed‐mother dyads appeared better at joint attention than depressed‐mother dyads, this difference was not statistically significant. Among the depressed‐mother dyads, joint attention was related to presence of a comorbid Axis I diagnosis (usually an anxiety disorder) versus a diagnosis of major depressive disorder (MDD) only. Surprisingly, dyads with mothers who met criteria for a comorbid diagnosis were better at joint attention than those with MDD only, despite the fact that those mothers were likely to have longer and more severe depressive histories. The relationship between comorbid status and joint attention was mediated by the mother's affect. Rationale for the paradoxical finding that the “more pathological” mothers had greater success in engaging in joint attention is discussed.     

Differences in How 12‐ and 24‐Month‐Olds Interpret the Gaze of Adults

This study examined the hypothesis that toddlers interpret an adult's head turn as evidence that the adult was looking at something, whereas younger infants interpret gaze based on an expectancy that an interesting object will be present on the side to which the adult has turned. Infants of 12 months and toddlers of 24 months were first shown that an adult head turn to the side predicted the activation of a remote‐controlled toy on that side of the room. After this connection had been demonstrated, participants were assigned to 2 conditions. In the head turn condition the toys were removed but the adult continued to produce head turns to the side. In the toy condition the adult stopped turning but the toys continued to be activated when the participant turned toward them. Results showed that, compared to 12‐month‐olds, 24‐month‐olds were more likely to continue to turn to the side when the adult continued to turn even though there was no longer anything of interest to see. In contrast, compared to 24‐month‐olds, 12‐month‐olds were, if anything, more likely to continue to turn to the side in the condition in which the adult stopped turning. The latter result was replicated in a condition in which the activation of the toy was not contingent on the child's own head turn. These results imply that the meaning of gaze following may change significantly over the 2nd year of life. For 12‐month‐olds, gaze is a useful predictor of where interesting sights may occur. In contrast, for 24‐month‐olds, gaze may be a signal that the adult is looking at something.     

Receptive Grammatical Knowledge of Familiar Content Words and Inflection in 16‐Month‐Olds

This study examines 16‐month‐olds' understanding of word order and inflectional properties of familiar nouns and verbs. Infants preferred grammatical sentences over ungrammatical sentences when the ungrammaticality was cued by both misplaced inflection and word order reversal of nouns and verbs. Infants were also sensitive to inflection alone as a cue to grammaticality, but not word order alone. The preference for grammatical sentence forms was also disrupted when adjacent function word cues were removed from the stimuli, and when familiar content words were replaced by nonce words. These results suggest that sensitivity to the relationship between functional morphemes and content words, rather than sensitivity to either independently, drives the development of early grammatical knowledge. Furthermore, infants showed some ability to generalize from familiar to nonce content word contexts.     

The Role of Context in the Categorization of Hybrid Toy Stimuli by 18‐Month‐Olds

Using a sequential touching procedure, we examined whether 18‐month‐olds could use different categorization strategies adaptively as a function of context. Infants were presented with test toys of land animals (quadrupeds), cars, and hybrids made by recombining car parts with animal parts. Infants who experienced a context emphasizing a taxonomic divide were subsequently more likely to form categories that reflected a taxonomic divide, whereas infants who experienced a context emphasizing a partonomic divide were subsequently more likely to form categories based on functional parts. These results suggest that 18‐month‐olds can adapt their categorization strategies flexibly in accordance with ambient contextual cues. This adds to the growing body of evidence that early categorization is flexible and not rigidly tied to characteristic features in the environment.     

Maternal Sensitivity and the Learning‐Promoting Effects of Depressed and Nondepressed Mothers' Infant‐Directed Speech

The hypothesis that aspects of current mother‐infant interactions predict an infant's response to maternal infant‐directed speech (IDS) was tested. Relative to infants of nondepressed mothers, those of depressed mothers acquired weaker voice‐face associations in response to their own mothers' IDS in a conditioned‐attention paradigm, although this was partially attributable to demographic differences between the 2 groups. The extent of fundamental frequency modulation (ΔF₀) in maternal IDS was smaller for infants of depressed than nondepressed mothers, but did not predict infant learning. However, Emotional Availability Scale ratings of maternal sensitivity, coded from videotapes of mothers and infants engaged in a brief play interaction, were significant predictors of infant learning, even after maternal depression, its demographic correlates, and antidepressant medication use had been taken into account. These findings are consistent with a role for experience‐dependent processes in determining the effects of IDS on infant learning.     

Development of Visual Selection in 3‐ to 9‐Month‐Olds: Evidence From Saccades to Previously Ignored Locations

We examined changes in the efficiency of visual selection over the first postnatal year with an adapted version of a spatial negative priming paradigm. In this task, when a previously ignored location becomes the target to be selected, responses to it are impaired, providing a measure of visual selection. Oculomotor latencies to target selection were the dependent measure. Each trial consisted of a prime and a probe presentation, separated by a 67‐, 200‐, or 550‐msec interstimulus interval (ISI), to test the efficiency of selection as a function of processing time. In the prime, the target was accompanied by a distractor item. In the probe, the target appeared either in the location formerly occupied by the distractor (repeated distractor trials) or in one of the other two locations (control trials). We tested 41 infants in each of 3 age groups (3, 6, and 9 months) on the three different ISIs. Nine‐month‐old infants' saccade latencies were slowed on repeated distractors relative to control trials, given sufficiently long ISIs. Saccade latencies in the youngest two age groups showed only facilitation on repeated distractor trials at short ISIs. These results suggest that visual selection efficiency is a function of the interaction of the processing limitations of a system with environmental conditions, in this case the time allotted for the selection process.     

Infant Preferences for Structural and Prosodic Properties of Infant‐Directed Speech in the Second Year of Life

While a large literature discusses young infants' preference for an infant‐directed speaking style, few studies have explored preferences after the first year. The present work compares infants' preference for two different properties of IDS speech: prosodic changes (primarily pitch and pitch variability) and structural properties (utterance length; lexical repetition). We found that both 12‐ and 16‐month‐old infants continued to prefer listening to speech with the prosodic properties of IDS, but neither age showed any preference for speech with the lexical repetition and short utterances typical of IDS.     

Picture Perception in Infants: Do 9‐Month‐Olds Attempt to Grasp Objects Depicted in Photographs?

Two experiments tested the DeLoache, Pierroutsakos, Uttal, Rosengren, and Gottlieb (1998 claim that 9‐month‐old infants attempt to grasp objects depicted in photographs. In Experiment 1, 9‐month‐olds viewed an object, a photograph of the object, and 2 flat, nonpictorial displays. On average, they reached for the photograph and nonpictorial displays with their hands approximately horizontal and close to the display surfaces, but reached for the object with their hands oriented obliquely and at significantly higher heights. The infants also exhibited similar behaviors when touching the photograph and nonpictorial displays. In Experiment 2, 9‐month‐olds exhibited similar behaviors when touching a photograph of an object and a photograph of textured carpet. The results of both experiments suggest that 9‐month‐olds treat photographs of objects as 2‐dimensional surfaces and not as graspable objects.     

Television Viewing Patterns in 6‐ to 18‐Month‐Olds: The Role of Caregiver–Infant Interactional Quality

The present study examines coviewing of Baby Mozart by 6‐ to 18‐month‐old infants and their caregivers under naturalistic conditions. We had two questions. First, extending the method of Barr, Zack, Garcia, and Muentener ( Infancy, 13 [2008], 30–56 ) to a younger population, we asked if age, prior exposure, and caregiver verbal input would predict infant looking to a Baby Mozart video from 6 to 18 months. Second, we asked if caregiver–infant interactional quality, defined as the amount of shared focus and turn taking between infant and caregiver, would be associated with infant looking time. We found that, in addition to the anticipated effect of prior exposure and caregiver verbal input, interactional quality measures were related to infant media‐directed looking. Infants who engaged in more shared focus and turn taking looked more to the program than infants who interacted less with their caregivers. These results are discussed in terms of social mediation of coviewing during early infancy.     

Role of Clinical Diagnosis and Medication Use in Effects of Maternal Depression on Infant‐Directed Speech

Infant‐directed (ID) speech was recorded from mothers as they interacted with their 4‐ to 12‐month‐old infants. Hierarchical regression analyses revealed that two variables, age of the mother and mother's diagnosed depression, independently accounted for significant proportions of the variance in the extent of change in fundamental frequency (ΔF0). Specifically, depressed mothers produced ID speech with smaller ΔF0 than did nondepressed mothers, and older mothers produced ID speech with larger ΔF0 than did younger mothers. Mothers who were taking antidepressant medication and who were diagnosed as being in at least partial remission produced ID speech with mean ΔF0 values that were comparable to those of nondepressed mothers. These results demonstrate explicit associations between major depressive disorder and an acoustic attribute of ID speech that is highly salient to young infants.