Preference For Infant-directed Speech Research Articles

Infants' Preference for ID Speech in Face and Voice Extends to a Non‐Native Language

ABSTRACTInfants prefer infant‐directed (ID) speech. Concerning talking faces, previous research showed that 3‐ and 5‐month‐olds prefer faces that produce native ID than native adult‐directed (AD) speech, regardless of background speech being ID, AD or silent. Here, we explored whether infants also show a preference for non‐native ID speech. We presented 3‐ and 6‐month‐old infants with pairs of talking faces, one producing non‐native ID speech and the other non‐native AD speech, either in silence (Experiment 1) or accompanied by non‐native ID or AD background speech (Experiment 2). Results from Experiment 1 showed an overall preference for the silent ID talking faces across both age groups, suggesting a reliance on cross‐linguistic, potentially universal cues for this preference. However, Experiment 2 showed that preference for ID faces was disrupted at 3 months when auditory speech was present (ID or AD). At 6 months, infants maintained a preference for ID talking faces, but only when accompanied by ID speech. These findings show that auditory non‐native speech interferes with infants' processing of ID talking faces. They also suggest that by 6 months, infants start associating ID features from faces and voices irrespective of language familiarity, suggesting that infants' ID preference may be universal and amodal.

Testing the relationship between preferences for infant-directed speech and vocabulary development: A multi-lab study.

From early on, infants show a preference for infant-directed speech (IDS) over adult-directed speech (ADS), and exposure to IDS has been correlated with language outcome measures such as vocabulary. The present multi-laboratory study explores this issue by investigating whether there is a link between early preference for IDS and later vocabulary size. Infants' preference for IDS was tested as part of the ManyBabies 1 project, and follow-up CDI data were collected from a subsample of this dataset at 18 and 24 months. A total of 341 (18 months) and 327 (24 months) infants were tested across 21 laboratories. In neither preregistered analyses with North American and UK English, nor exploratory analyses with a larger sample did we find evidence for a relation between IDS preference and later vocabulary. We discuss implications of this finding in light of recent work suggesting that IDS preference measured in the laboratory has low test-retest reliability.

Limited evidence of test-retest reliability in infant-directed speech preference in a large preregistered infant experiment.

Test-retest reliability-establishing that measurements remain consistent across multiple testing sessions-is critical to measuring, understanding, and predicting individual differences in infant language development. However, previous attempts to establish measurement reliability in infant speech perception tasks are limited, and reliability of frequently used infant measures is largely unknown. The current study investigated the test-retest reliability of infants' preference for infant-directed speech over adult-directed speech in a large sample (N=158) in the context of the ManyBabies1 collaborative research project. Labs were asked to bring in participating infants for a second appointment retesting infants on their preference for infant-directed speech. This approach allowed us to estimate test-retest reliability across three different methods used to investigate preferential listening in infancy: the head-turn preference procedure, central fixation, and eye-tracking. Overall, we found no consistent evidence of test-retest reliability in measures of infants' speech preference (overall r=0.09, 95% CI [-0.06,0.25]). While increasing the number of trials that infants needed to contribute for inclusion in the analysis revealed a numeric growth in test-retest reliability, it also considerably reduced the study's effective sample size. Therefore, future research on infant development should take into account that not all experimental measures may be appropriate for assessing individual differences between infants. RESEARCH HIGHLIGHTS: We assessed test-retest reliability of infants' preference for infant-directed over adult-directed speech in a large pre-registered sample (N=158). There was no consistent evidence of test-retest reliability in measures of infants' speech preference. Applying stricter criteria for the inclusion of participants may lead to higher test-retest reliability, but at the cost of substantial decreases in sample size. Developmental research relying on stable individual differences should consider the underlying reliability of its measures.

Evidence for Infant-directed Speech Preference Is Consistent Across Large-scale, Multi-site Replication and Meta-analysis.

There is substantial evidence that infants prefer infant-directed speech (IDS) to adult-directed speech (ADS). The strongest evidence for this claim has come from two large-scale investigations: i) a community-augmented meta-analysis of published behavioral studies and ii) a large-scale multi-lab replication study. In this paper, we aim to improve our understanding of the IDS preference and its boundary conditions by combining and comparing these two data sources across key population and design characteristics of the underlying studies. Our analyses reveal that both the meta-analysis and multi-lab replication show moderate effect sizes (d ≈ 0.35 for each estimate) and that both of these effects persist when relevant study-level moderators are added to the models (i.e., experimental methods, infant ages, and native languages). However, while the overall effect size estimates were similar, the two sources diverged in the effects of key moderators: both infant age and experimental method predicted IDS preference in the multi-lab replication study, but showed no effect in the meta-analysis. These results demonstrate that the IDS preference generalizes across a variety of experimental conditions and sampling characteristics, while simultaneously identifying key differences in the empirical picture offered by each source individually and pinpointing areas where substantial uncertainty remains about the influence of theoretically central moderators on IDS preference. Overall, our results show how meta-analyses and multi-lab replications can be used in tandem to understand the robustness and generalizability of developmental phenomena.

Maternal Thiamine Supplementation Promotes Infants’ Language Processing at 24 Weeks

ObjectivesIn 2005, researchers observed a link between infants’ access to thiamine (vitamin B1) and their subsequent language functioning: infants fed formula that inadvertently lacked thiamine later displayed significant delays in language and motor development. In the context of a double-blind, randomized, controlled trial, the present research provided the first experimental test of a relationship between early life thiamine exposure and infants’ early language processing. Methods335 lactating mothers were randomly assigned to receive capsules containing either 0, 1.2, 2.4, or 10 mg of thiamine daily, from 2 weeks postpartum until infants were 24 weeks. We assessed the integrity of 24-week-old infants’ developing system for language processing by measuring the extent to which they displayed attentional enhancement in response to infant-directed speech (IDS) relative to adult-directed speech (ADS). Such IDS-related attentional enhancement implies that infants can differentiate IDS from ADS, which requires underlying skills for analysis of the complex stream of sound that human speech embodies. Of the 335 infants in the study, analyzable data for the IDS preference task were available for 251. ResultsAs predicted, a greater-than-chance percentage of all infants displayed enhanced attention to IDS relative to ADS, replicating prior research (one-sample t(250) = 3.06, P = 0.002). The magnitude of the IDS-elicited attentional-enhancement increased significantly in relation to the thiamine dose that lactating mothers received (beta-weight 0.007, t = 2.57, P = 0.011). Notably, however, when supplementation groups were examined separately, only infants whose mothers received the 10 mg daily supplement displayed a statistically significant IDS-related attentional enhancement (10 mg group: one-sample t(63) = 4.14, P = 0.000; all other groups t’s < 1.41, P’s > 0.16). ConclusionsTaken together, these findings confirm a link between infants’ post-natal access to thiamine and their language processing facility at 24 weeks. The findings both showcase the value of the IDS preference task for monitoring the integrity of infants’ language processing, and underscore the importance of adequate thiamine for ensuring infants’ optimal language development. Funding SourcesBill & Melinda Gates Foundation and the New York Academy of Sciences.

A multi-lab study of bilingual infants: Exploring the preference for infant-directed speech.

From the earliest months of life, infants prefer listening to and learn better from infant-directed speech (IDS) than adult-directed speech (ADS). Yet, IDS differs within communities, across languages, and across cultures, both in form and in prevalence. This large-scale, multi-site study used the diversity of bilingual infant experiences to explore the impact of different types of linguistic experience on infants' IDS preference. As part of the multi-lab ManyBabies 1 project, we compared lab-matched samples of 333 bilingual and 385 monolingual infants' preference for North-American English IDS (cf. ManyBabies Consortium, 2020: ManyBabies 1), tested in 17 labs in 7 countries. Those infants were tested in two age groups: 6-9 months (the younger sample) and 12-15 months (the older sample). We found that bilingual and monolingual infants both preferred IDS to ADS, and did not differ in terms of the overall magnitude of this preference. However, amongst bilingual infants who were acquiring North-American English (NAE) as a native language, greater exposure to NAE was associated with a stronger IDS preference, extending the previous finding from ManyBabies 1 that monolinguals learning NAE as a native language showed a stronger preference than infants unexposed to NAE. Together, our findings indicate that IDS preference likely makes a similar contribution to monolingual and bilingual development, and that infants are exquisitely sensitive to the nature and frequency of different types of language input in their early environments.

Maternal input and infants' response to infant-directed speech.

Caregivers typically use an exaggerated speech register known as infant-directed speech (IDS) in communication with infants. Infants prefer IDS over adult-directed speech (ADS) and IDS is functionally relevant in infant-directed communication. We examined interactions among maternal IDS quality, infants' preference for IDS over ADS, and the functional relevance of IDS at 6 and 13months. While 6-month-olds showed a preference for IDS over ADS, 13-month-olds did not. Differences in gaze following behavior triggered by speech register (IDS vs. ADS) were found in both age groups. The degree of infants' preference for IDS (relative to ADS) was linked to the quality of maternal IDS infants were exposed to. No such relationship was found between gaze following behavior and maternal IDS quality and infants' IDS preference. The results speak to a dynamic interaction between infants' preference for different kinds of social signals and the social cues available to them.

Exploring priming effects of social and non-social attention getters on older infants’ preferences for infant-directed speech

In infant research, various auditory/visual events are often used as attention getters to orient infants to a screen and alert them to upcoming information for their detection, discrimination, and/or recognition. Importantly, the influence of attention-getters on infants’ performance has rarely been systematically evaluated, even though these attention cues could be affecting subsequent information processing. This study investigated whether specific attention-getters could prime infants’ preferences for infant-directed speech (IDS) compared to adult-directed speech (ADS). Both a non-social and a social prime were chosen with the prediction that the social prime would strengthen infants' attention to IDS on a subsequent trial, but the non-social prime would have no differential effect on subsequent attention to either speech type. A total of 20 12- to 18-month old infants were presented with either a nonsocial (rotating form + chimes) or social (smiling female + voice) prime in an infant-controlled, speech preference procedure with both IDS and ADS speech types. Given previous research, we predicted that infants would show significantly more attention on trials during which looking produced IDS, but that this preference would be significantly augmented for infants in the condition receiving a social attention-getter before each trial. Results did not bear out this prediction, although we found a consistent, robust preference for IDS. The results will be discussed in terms of why these attention getters did not affect subsequent processing of two very different speech types, and what future modifications may be necessary in order to examine roles of attention getters in affecting experimental outcomes in infancy research. A secondary benefit of the findings is that we empirically established a growing preference for IDS in infants as old as 18-months of age.

Quantifying Sources of Variability in Infancy Research Using the Infant-Directed-Speech Preference

Psychological scientists have become increasingly concerned with issues related to methodology and replicability, and infancy researchers in particular face specific challenges related to replicability: For example, high-powered studies are difficult to conduct, testing conditions vary across labs, and different labs have access to different infant populations. Addressing these concerns, we report on a large-scale, multisite study aimed at (a) assessing the overall replicability of a single theoretically important phenomenon and (b) examining methodological, cultural, and developmental moderators. We focus on infants’ preference for infant-directed speech (IDS) over adult-directed speech (ADS). Stimuli of mothers speaking to their infants and to an adult in North American English were created using seminaturalistic laboratory-based audio recordings. Infants’ relative preference for IDS and ADS was assessed across 67 laboratories in North America, Europe, Australia, and Asia using the three common methods for measuring infants’ discrimination (head-turn preference, central fixation, and eye tracking). The overall meta-analytic effect size (Cohen’s d) was 0.35, 95% confidence interval = [0.29, 0.42], which was reliably above zero but smaller than the meta-analytic mean computed from previous literature (0.67). The IDS preference was significantly stronger in older children, in those children for whom the stimuli matched their native language and dialect, and in data from labs using the head-turn preference procedure. Together, these findings replicate the IDS preference but suggest that its magnitude is modulated by development, native-language experience, and testing procedure.

ManyBabies1: Infants' preference for infant-directed speech

There is growing concern about the replicability of basic findings in psychology, including in infancy research (Frank et al., 2017). ManyBabies is a large-scale international collaboration to replicate basic empirical findings in infancy. Our first project is ManyBabies1, which examines infant preference for infant-directed speech (IDS). Over 70 laboratories collaborated to collect data from over 2500 infants aged 3–15 months. Stimuli consisted of speech produced in a semi-naturalistic elicitation task where fifteen different mothers who spoke North American English talked about a series of novel and familiar objects to their infant and separately to an experimenter. A set of 8 passages each in IDS and adult-directed speech (ADS) were created after a comprehensive norming process. Infants were tested in 3 primary methods: eyetracking, central fixation and headturn preference. Overall, the effect of preference for IDS was replicated, although the calculated effect was smaller than that reported by meta-analysis (Dunst et al., 2012, metalab.stanford.edu). Preference for IDS increased across development. The success of this project shows that infant research conducted collaboratively and at-scale can answer new questions about the replicability and generalizability of infant findings across different laboratory, methodological, and infant participant characteristics.

ManyBabies1 part 2: Influences of language experience on infant-directed speech preference

ManyBabies1, our first effort at a large scale collaborative infant experimental study, provided a conceptual replication of the well-known phenomenon of infant preference for the characteristics of Infant-directed speech (IDS). One important question that has largely been unanswered by extant literature is how much the IDS preference is dependent on experience with a specific language. How do infants respond to IDS that is in a non-native variety, and how does their listening affect this preference? ManyBabies 1 used a consistent stimulus set of North-American English (NAE), which allowed us to answer this questions using two approaches. First, because participating ManyBabies 1 labs were located around the world, we were able to compare monolingual infants from a range of native-language backgrounds. We found that the preference for North American English IDS was larger for infants whose native language was NAE than for infants who had a different native language. Second, we conducted a sister project, ManyBabies 1 Bilingual, which tested infants from a variety of bilingual backgrounds. Bilinguals have similar total language experience and maturation as monolinguals, but their experience is divided across two or more languages. Planned analyses will examine monolingual-bilingual differences, and “dose-response” effects of exposure to NAE.

Preference for Infant-Directed Speech in Infants With Hearing Aids: Effects of Early Auditory Experience.

It is well established that (a) infants prefer listening to infant-directed speech (IDS) over adult-directed speech (ADS), and (b) IDS facilitates speech, language, and cognitive development, compared with ADS. The main purpose of this study was to determine whether infants with hearing aids (HAs), similar to their peers with normal hearing (NH), show a listening preference for IDS over ADS. A total of 42 infants participated in the study. In Experiment 1, 9 infants with hearing loss, who had approximately 12 months of experience (mean chronological age of 17.57 months) with HAs, and 9 infants with NH, who had similar chronological age (17.54 months), were tested. In Experiment 2, 10 infants with hearing loss, who had approximately 4 months of experience (mean chronological age of 9.86 months) with HAs, and 14 infants with NH, who had similar chronological age (9.09 months), were tested. Infants were tested on their listening preference in 3 randomized blocks: IDS versus silence, ADS versus silence, and IDS versus ADS blocks, using the central fixation preference procedure. Experiment 1 showed that infants with HAs, similar to their peers with NH, listened longer to both IDS and ADS relative to silence; however, neither infants with HAs nor infants with NH showed a listening preference for IDS over ADS. In Experiment 2, both infants with HAs and infants with NH showed a listening preference for IDS and ADS relative to silence; in addition, both groups preferred listening to IDS over ADS. Infants with HAs appear to have sufficient access to the acoustic cues in the speech that allow them to develop an age-equivalent IDS preference. This may be attributed to a combination of being able to use the hearing they do have before receiving HAs and early device fitting. Given previously demonstrated positive associations between IDS preference and language development, this research encourages early interventions focusing on maximizing early auditory experience in infants with hearing loss. https://doi.org/10.23641/asha.6906365.

Is infant-directed speech interesting because it is surprising? – Linking properties of IDS to statistical learning and attention at the prosodic level

The exaggerated intonation and special rhythmic properties of infant-directed speech (IDS) have been hypothesized to attract infants’ attention to the speech stream. However, there has been little work actually connecting the properties of IDS to models of attentional processing or perceptual learning. A number of such attention models suggest that surprising or novel perceptual inputs attract attention, where novelty can be operationalized as the statistical (un)predictability of the stimulus in the given context. Since prosodic patterns such as F0 contours are accessible to young infants who are also known to be adept statistical learners, the present paper investigates a hypothesis that F0 contours in IDS are less predictable than those in adult-directed speech (ADS), given previous exposure to both speaking styles, thereby potentially tapping into basic attentional mechanisms of the listeners in a similar manner that relative probabilities of other linguistic patterns are known to modulate attentional processing in infants and adults. Computational modeling analyses with naturalistic IDS and ADS speech from matched speakers and contexts show that IDS intonation has lower overall temporal predictability even when the F0 contours of both speaking styles are normalized to have equal means and variances. A closer analysis reveals that there is a tendency of IDS intonation to be less predictable at the end of short utterances, whereas ADS exhibits more stable average predictability patterns across the full extent of the utterances. The difference between IDS and ADS persists even when the proportion of IDS and ADS exposure is varied substantially, simulating different relative amounts of IDS heard in different family and cultural environments. Exposure to IDS is also found to be more efficient for predicting ADS intonation contours in new utterances than exposure to the equal amount of ADS speech. This indicates that the more variable prosodic contours of IDS also generalize to ADS, and may therefore enhance prosodic learning in infancy. Overall, the study suggests that one reason behind infant preference for IDS could be its higher information value at the prosodic level, as measured by the amount of surprisal in the F0 contours. This provides the first formal link between the properties of IDS and the models of attentional processing and statistical learning in the brain. However, this finding does not rule out the possibility that other differences between the IDS and ADS also play a role.

Infant-Directed Speech Enhances Attention to Speech in Deaf Infants With Cochlear Implants.

Both theoretical models of infant language acquisition and empirical studies posit important roles for attention to speech in early language development. However, deaf infants with cochlear implants (CIs) show reduced attention to speech as compared with their peers with normal hearing (NH; Horn, Davis, Pisoni, & Miyamoto, 2005; Houston, Pisoni, Kirk, Ying, & Miyamoto, 2003), which may affect their acquisition of spoken language. The main purpose of this study was to determine (a) whether infant-directed speech (IDS) enhances attention to speech in infants with CIs, as compared with adult-directed speech (ADS), and (b) whether the degree to which infants with CIs pay attention to IDS is associated with later language outcomes. We tested 46 infants-12 prelingually deaf infants who received CIs before 24 months of age and had 12 months of hearing experience (CI group), 22 hearing experience-matched infants with NH (NH-HEM group), and 12 chronological age-matched infants with NH (NH-CAM group)-on their listening preference in 3 randomized blocks: IDS versus silence, ADS versus silence, and IDS versus ADS. We administered the Preschool Language Scale-Fourth Edition (PLS-4; Zimmerman, Steiner, & Pond, 2002) approximately 18 months after implantation to assess receptive and expressive language skills of infants with CIs. In the IDS versus silence block, all 3 groups looked significantly longer to IDS than to silence. In the ADS versus silence block, both the NH-HEM and NH-CAM groups looked significantly longer to ADS relative to silence; however, the CI group did not show any preference. In the IDS versus ADS block, whereas both the CI and NH-HEM groups preferred IDS over ADS, the NH-CAM group looked equally long to IDS and ADS. IDS preference quotient among infants with CIs in the IDS versus ADS block was associated with PLS-4 Auditory Comprehension and PLS-4 Expressive Communication measures. Two major findings emerge: (a) IDS enhances attention to speech in deaf infants with CIs; (b) the degree of IDS preference over ADS relates to language development in infants with CIs. These results support a focus on input in developing intervention strategies to mitigate the effects of hearing loss on language development in infants with hearing loss.

Preference for infant-directed speech in preterm infants

The current study explores the effects of exposure to maternal voice on infant sucking in preterm infants. Twenty-four preterm infants averaging 35 weeks gestational age were divided randomly into two groups. A contingency between high-amplitude sucking and presentation of maternal voice was instituted for one group while the other group served as a yoked control. No significant differences were observed in sucking of the two groups, but the degree of pitch modulation of the maternal voice predicted an increase in the rate of infant sucking.

Linking Infant-Directed Speech and Face Preferences to Language Outcomes in Infants at Risk for Autism Spectrum Disorder

In this study, the authors aimed to examine whether biases for infant-directed (ID) speech and faces differ between infant siblings of children with autism spectrum disorder (ASD) (SIBS-A) and infant siblings of typically developing children (SIBS-TD), and whether speech and face biases predict language outcomes and risk group membership. Thirty-six infants were tested at ages 6, 8, 12, and 18 months. Infants heard 2 ID and 2 adult-directed (AD) speech passages paired with either a checkerboard or a face. The authors assessed expressive language at 12 and 18 months and general functioning at 12 months using the Mullen Scales of Early Learning (Mullen, 1995). Both infant groups preferred ID to AD speech and preferred faces to checkerboards. SIBS-TD demonstrated higher expressive language at 18 months than did SIBS-A, a finding that correlated with preferences for ID speech at 12 months. Although both groups looked longer to face stimuli than to the checkerboard, the magnitude of the preference was smaller in SIBS-A and predicted expressive vocabulary at 18 months in this group. Infants' preference for faces contributed to risk-group membership in a logistic regression analysis. Infants at heightened risk of ASD differ from typically developing infants in their preferences for ID speech and faces, which may underlie deficits in later language development and social communication.

Melodic versus intonational coding of communicative functions: A comparison of tonal contours in infant-directed song and speech.

ABSTRACT - Global intonational contours of infantdirected speech are said to serve effective communicative functions. For example, steep rising contours are thought to arouse an infant while smoothly falling contours are thought to be soothing. Several researchers (e.g., Cordes, 2005; Papousek, 1996; Unyk, Trehub, Trainar, & Schellenberg, 1992) proposed that the melodic contours in nursery songs should fallow the same communicative principles as in speech. In this study, melodic and intonational contours in play contexts were compared in three languages in order to determine 1) whether infant-directed speech and song are similar in the composition of their typical contours, and 2) whether there are differences across languages. Evidence from soothing contexts is also taken into account. The material was collected from 43 German-, Frenchand Russian-speaking parents singing or speaking to their 2- to 12- month-old infants. Tonal contour types in each register were assessed adopting protocols based on Cordes (2005). The results confirm the similarity between infant-directed speech and song in play contexts, but some differences occur in soothing contexts. Languagespecific patterns are discussed, and it is put forward that it would be valuable to intensify research into the language-specific basis of infant-directed communication. KEYWORDS - Infant-directed speech, song, contour forms, communicative function In the presence of an infant, adults often unconsciously change their way of talking and singing. They slow down in tempo, use a higher overall pitch level, show more pitch variability, make more pauses and repeat their utterances (overview in Cruttenden, 1994; Trehub, 2003). In their first year of life, infants clearly prefer to listen to infant-directed speech (or motherese) and song than to adult-directed speech and song (Cooper, Abraham, Berman, & Staska, 1997; Fernald, 1984; Fernald & Kuhl, 1987; Nakata & Trehub, 2004; Trainor, 1996; Trehub & Trainor, 1998). Infants' preference for infant-directed speech is thought to be mostly due to the tonal structure of the signal (Fernald & Kuhl, 1987): adults use a wider frequency range, a higher speech register and salient tonal contours when addressing children (Fernald & Simon, 1984; Fernald et al., 1989; Gavrilova, 2001; Stern, Spieker, & MacKain, 1982). Infant-directed songs are also sung at a higher pitch level (Trainor & Zacharias, 1998), in a smiling tone and with more jitter and shimmer in the voice (Trainor, 1996; Trainor, Clark, Huntley, & Adams, 1997), which might be due to a higher emotional involvement of the singer (Trehub & Trainor, 1998). Fernald (1989), Papousek (1996), and Papousek, Papousek, and Symmes (1991) showed that there is a narrow inventory of tonal contour types in infant-directed speech used by parents to fulfill distinct communicative functions. Rising contours encourage a turn or elicit attention (especially at the age of 2 and 3 months, see Henning, Striano, and Lieven, 2005), bell-shaped contours close a turn or signal approval, steeply falling contours with abrupt onsets are used for warnings, disapproval and prohibitions whereas smoothly falling contours soothe and comfort the infant (see Figure 1). These functions were initially taken to be cross-linguistic universale (Grieser & Kuhl, 1988; Papousek et al., 1991), though further research showed some variations in tonal features and in the frequency of contour types across language and cultural context, sex and age of the infant (Kitamura & Burnham, 2003; Kitamura, Thanavishuth, Burnham, & Luksaneeyanawin, 2001; Lam & Kitamura, 2006; Rabain-Jamin & Sabeau-Jouannet, 1997). In the first year of life, infants attend particularly to the global shape of tonal/melodic contours in speech and song (Fernald & Kuhl, 1987; Trehub, Bull, & Thorpe, 1984). Thus, tonal contours with communicative functions might help infants to establish a first semantic-pragmatic relation between phonetic form and global referential meaning. …

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.

Changes in Preference for Infant-Directed Speech in Low and Moderate Noise by 4.5- to 13-Month-Olds.

Although a large literature discusses infants' preference for infant-directed speech (IDS), few studies have examined how this preference might change over time or across listening situations. The work reported here compares infants' preference for IDS while listening in a quiet versus a noisy environment, and across 3 points in development: 4.5 months of age, 9 months of age, and 13 months of age. Several studies have suggested that IDS might help infants to pick out speech in the context of noise (Colombo, Frick, Ryther, Coldren, & Mitchell, 1995; Fernald, 1984; Newman, 2003); this might suggest that infants' preference for IDS would increase in these settings. However, this was not found to be the case; at all 3 ages, infants showed similar advantage (or lack thereof) for IDS as compared to adult-directed speech when presented in noise versus silence. There was, however, a significant interaction across ages: Infants aged 4.5 months showed an overall preference for IDS, whereas older infants did not, despite listening to the same stimuli. The lack of an effect with older infants replicates and extends recent findings by Hayashi, Tamekawa, and Kiritani (2001), suggesting that the variations in fundamental frequency and affect are not sufficient cues to IDS for older infants.

Preference for Infant-directed Speech in the First Month after Birth

2 experiments examined behavioral preferences for infant-directed (ID) speech over adult-directed (AD) speech in young infants. Using a modification of the visual-fixation-based auditory-preference procedure, Experiments 1 and 2 examined whether 12 1-month-old and 16 2-day-old infants looked longer at a visual stimulus when looking produced ID as opposed to AD speech. The results showed that both 1-month-olds and newborns preferred ID over AD speech. Although the absolute magnitude of the ID speech preference was significantly greater, with the older infants showing longer looking durations than the younger infants, subsequent analyses showed no significant difference in the relative magnitude of this effect. Differences in overall looking times between the 2 groups apparently reflect task variables rather than differences in speech processing. These results suggest that infants' preference for the exaggerated prosodic features of ID speech is present from birth and may not depend on any specific postnatal experience. However, the possible role of prenatal auditory experience with speech is considered.