Headturn Preference Procedure Research Articles

Behavioral methods in infancy: pitfalls of single measures

This paper outlines the principal behavioral methods used to study music processing in infancy. The advantages of conditioning procedures are offset by high attrition rates and restrictions on the stimuli that can be used. The head-turn preference procedure is more user-friendly but poses greater interpretive challenges. In view of the multidimensional nature of infant attention, no single response measure, whether behavioral, physiological, or neural, can provide unambiguous information about music processing in infancy. Greater use of ecologically valid stimuli is likely to generate increased cooperation from infants and greater generality of the findings.

Evidence for Language-Specific Influence on the Preference of Stress Patterns in Infants Learning an Iambic Language (Hebrew)

The ability of infants to develop recognition of a common stress pattern that is language specific has been tested mainly in trochaic languages with a strong-weak (SW) stress pattern. The goals of the present study were: (a) to test Hebrew-learning infants on their stress pattern preference in the Hebrew language, for which the weak-strong (WS) stress pattern is the common one, and (b) to test whether the infants would generalize any preference for the common stress pattern in Hebrew to English words, which belong to a different rhythmic class. Fifty-six 9-month-old Hebrew-learning infants were tested on their preference for SW and WS stress patterns using Hebrew and English bisyllabic words with the head-turn preference procedure. The infants showed preference for WS Hebrew words but not for SW English words. Hebrew-learning infants recognize the common stress pattern in their native language, supporting language-specific distributional learning by infants. This recognition, however, is not generalized to a foreign language with different prosodic characteristics.

Prosodic Cues to Word Order: What Level of Representation?

Within language, systematic correlations exist between syntactic structure and prosody. Prosodic prominence, for instance, falls on the complement and not the head of syntactic phrases, and its realization depends on the phrasal position of the prominent element. Thus, in Japanese, a functor-final language, prominence is phrase-initial, and realized as increased pitch (^ Tōkyō ni “Tokyo to”), whereas in French, English, or Italian, functor-initial languages, it manifests itself as phrase-final lengthening (to Rome). Prosody is readily available in the linguistic signal even to the youngest infants. It has, therefore, been proposed that young learners might be able to exploit its correlations with syntax to bootstrap language structure. In this study, we tested this hypothesis, investigating how 8-month-old monolingual French infants processed an artificial grammar manipulating the relative position of prosodic prominence and word frequency. In Condition 1, we created a speech stream in which the two cues, prosody and frequency, were aligned, frequent words being prosodically non-prominent and infrequent ones being prominent, as is the case in natural language (functors are prosodically minimal compared to content words). In Condition 2, the two cues were misaligned, with frequent words carrying prosodic prominence, unlike in natural language. After familiarization with the aligned or the misaligned stream in a headturn preference procedure, we tested infants’ preference for test items having a frequent word initial or a frequent word final word order. We found that infants’ familiarized with the aligned stream showed the expected preference for the frequent word initial test items, mimicking the functor-initial word order of French. Infants in the misaligned condition showed no preference. These results suggest that infants are able to use word frequency and prosody as early cues to word order and they integrate them into a coherent representation.

How each prosodic boundary cue matters: evidence from german infants.

Previous studies have revealed that infants aged 6–10 months are able to use the acoustic correlates of major prosodic boundaries, that is, pitch change, preboundary lengthening, and pause, for the segmentation of the continuous speech signal. Moreover, investigations with American-English- and Dutch-learning infants suggest that processing prosodic boundary markings involves a weighting of these cues. This weighting seems to develop with increasing exposure to the native language and to underlie crosslinguistic variation. In the following, we report the results of four experiments using the headturn preference procedure to explore the perception of prosodic boundary cues in German infants. We presented 8-month-old infants with a sequence of names in two different prosodic groupings, with or without boundary markers. Infants discriminated both sequences when the boundary was marked by all three cues (Experiment 1) and when it was marked by a pitch change and preboundary lengthening in combination (Experiment 2). The presence of a pitch change (Experiment 3) or preboundary lengthening (Experiment 4) as single cues did not lead to a successful discrimination. Our results indicate that pause is not a necessary cue for German infants. Pitch change and preboundary lengthening in combination, but not as single cues, are sufficient. Hence, by 8 months infants only rely on a convergence of boundary markers. Comparisons with adults’ performance on the same stimulus materials suggest that the pattern observed with the 8-month-olds is already consistent with that of adults. We discuss our findings with respect to crosslinguistic variation and the development of a language-specific prosodic cue weighting.

Infants Exposed to Fluent Natural Speech Succeed at Cross-Gender Word Recognition

To examine the possibility that early signal-to-word form mapping capabilities are robust enough to handle substantial indexical variation in the realization of words. Two groups of 7.5-month-olds were tested with the Headturn Preference Procedure. Half of the infants were exposed to words embedded in passages spoken by their mothers and tested on lists of trained and novel isolated words spoken by their fathers. The other half of the infants were yoked pairs listening to unfamiliar speakers. In the test phase, infants listened longer to trained than to novel words, indicating that they successfully segmented the words from the passages. This result was not modulated by infants' familiarity with the speaker. Under more naturalistic listening conditions, 7.5-month-olds exhibit the ability to recognize words in the face of substantial indexical variation regardless of whether speakers are familiar. This suggests that early word representations are, at least to some extent, independent of the speaker's gender and may reflect sophisticated abstraction capabilities on the part of the infants, which would render extreme episodic models of early speech perception untenable. Additional research using similarly ecologically valid testing methods is called for to elucidate the precise nature of early word representations.

Speaker adaptation in infancy: The role of lexical knowledge

The acoustic realization of words varies greatly between speakers. While adults easily adapt to speaker idiosyncrasies, infants do not possess mature signal-to-word mapping abilities. As a result, the variability in the speech signal has been claimed to impede their word recognition. This study examines whether exposure to a speaker may allow infants to better accommodate that speaker's accent. Using the Headturn Preference Procedure, 15-month-olds were presented with lists containing either familiar (e.g., ball) or unfamiliar words (e.g., bog). In experiment 1, these words were produced in infants' own accent (Canadian English); in experiment 2, they were produced in a foreign accent (Australian English). Comparable to previous work (Best etal., 2009), only infants presented with their own accent preferred to listen to familiar over unfamiliar words. Thus, without access to speaker characteristics, word recognition is limited to familiar accents. In experiment 3, the same Australian-accented stimuli were preceded by exposure to the Australian speaker. Speaker adaptation tended to correlate with the infants' vocabulary size, with greater vocabularies being indicative to more robust adaptation. We are currently testing whether vocabulary size is a mediating factor caused by general processing abilities or whether speaker adaptation is lexically driven.

A cross-linguistic investigation of word segmentation by monolingual infants learning Spanish and English

Infants' ability to find words in fluent speech is affected by their language experience. The focus of this study was the extent to which monolingual Spanish- and monolingual English-learning 8-month-old infants' segmentation abilities are tied to their familiarity with the rhythmic properties of their native language. Spanish and English are considered to belong to different rhythm classes; the former is syllable-timed, whereas the latter is stress-timed. However, in both languages CVC.CV words are predominantly trochaic—i.e., words with stress on the initial syllable (Cutler Carter, 1984; Pons Bosch, 2010). We tested segmentation of trochaic words of the form CVC.CV in Spanish and English. Spanish word segmentation was tested using the Headturn Preference Procedure and English word segmentation using the visual fixation procedure. According to Jusczyk et al.'s rhythm hypothesis, infants should fail to segment words in a rhythmically different language. Contrary to the rhythm hypothesis, preliminary data indicate that Spanish-learning infants are successful in segmenting trochees in both Spanish and English. Thus, successful transfer of word segmentation abilities by infants seems to depend upon a match in the prosodic shape of the target word across the two languages.

Examining infants' preferences for tempo in lullabies and playsongs.

Caregivers around the world sing to their infants. Infants not only prefer to listen to infant-directed singing over adult-directed singing, but infant-directed singing also serves a function, communicating affective information to preverbal infants to aid in adjusting arousal levels. Pitch variation has previously been identified as one performance feature that may help to convey the message. Earlier research has indicated that infants' pitch preferences are context dependent, suggesting that infants are tuned in to the communicative intent of infant-directed singing. However, there are several other performance-based features present in infant-directed singing that may also contribute to the affective message. The current study examined the role of context on infants' tempo preferences in sung playsongs and lullabies. Using a head-turn preference procedure, we measured 24 preverbal infants' natural preferences for foreign language playsongs and lullabies as a function of tempo. Infants showed a preference for fast over slow tempo playsongs, but no such context dependent preference was found within lullabies. Results partially support the role of tempo as a communicative feature of infant directed singing.

Do production patterns influence the processing of speech in prelinguistic infants?

The headturn preference procedure was used to test 18 infants on their response to three different passages chosen to reflect their individual production patterns. The passages contained nonwords with consonants in one of three categories: (a) often produced by that infant (‘own’), (b) rarely produced by that infant but common at that age (‘other’), and (c) not generally produced by infants. Infants who had a single ‘own’ consonant showed no significant preference for either ‘own’ (a) or ‘other’ (b) passages. In contrast, infants’ with two ‘own’ consonants exhibited greater attention to ‘other’ passages (b). Both groups attended equally to the passage featuring consonants rarely produced by infants of that age (c). An analysis of a sample of the infant-directed speech ruled out the mothers’ speech as a source of the infant preferences. The production-based shift to a focus on the ‘other’ passage suggests that nascent production abilities combine with emergent perceptual experience to facilitate word learning.

Six-month-old infants discriminate voicing on the basis of temporal envelope cues (L)

Young deaf children using a cochlear implant develop speech abilities on the basis of speech temporal-envelope signals distributed over a limited number of frequency bands. A Headturn Preference Procedure was used to measure looking times in 6-month-old, normal-hearing infants during presentation of repeating or alternating sequences composed of different tokens of /aba/and /apa/ processed to retain envelope information below 64 Hz while degrading temporal fine structure cues. Infants attended longer to the alternating sequences, indicating that they perceive the voicing contrast on the basis of envelope cues alone in the absence of fine spectral and temporal structure information.

Discrimination between mothers’ infant- and adult-directed speech using hidden Markov models

Infant-directed speech (IDS) has the important functions of capturing the infants’ attention and maintaining communication between the mother and the infant. It is known that three acoustic components (F0, F0 range, and tempo) in IDS and adult-directed speech (ADS) are different. However, it is not easy to discriminate between IDS and ADS using procedural approaches due to the wide range of individual differences. In this paper, we propose a novel approach to discriminate between IDS and ADS that uses mel-frequency cepstral coefficient and a hidden Markov model-based speech discrimination algorithm; this approach is not based on the prosodic features of F0, F0 range, and tempo. The average discrimination accuracy of the proposed algorithm is 84.34%. The objective accuracy of the discrimination models have been confirmed using the head-turn preference procedure, which measures infants’ listening duration to auditory stimuli of IDS and ADS. These results suggest that the proposed algorithm may enable a robust and reliable classification of mothers’ speech and infant attention to the mothers’ speech may depend on IDS clarity.

Infants' Discrimination of Familiar and Unfamiliar Accents in Speech.

This study investigates infants' discrimination abilities for familiar and unfamiliar regional English accents. Using a variation of the head-turn preference procedure, 5-month-old infants demonstrated that they were able to distinguish between their own South-West English accent and an unfamiliar Welsh English accent. However, this distinction was not seen when two unfamiliar accents (Welsh English and Scottish English) were presented to the infants, indicating they had not acquired the general ability to distinguish between regional varieties, but only the distinction between their home accent and unfamiliar regional variations. This ability was also confirmed with 7-month-olds, challenging recent claims that infants lose their sensitivity to dialects at around that age. Taken together, our results argue in favor of an early sensitivity to the intonation system of languages, and to the early learning of accent-specific intonation and potentially segmental patterns. Implications for the development of accent normalization abilities are discussed.

Function word facilitate word segmentation.

Infants’ word segmentation is facilitated by bottom‐up cues, such as prosodic cues (stress‐patterns, position in a sentence, etc.). Research shows that infants also use top‐down cues, i.e., known words, to segment new words [Bortfeld et al. (2005); “mommy” and the child’s name]. In two experiments, infants were tested on their ability to use a known function word “the” to segment vowel‐initial words (the ability to segment them does not appear until 13.5–16 months), without any additional bottom‐up cues. In experiment 1, using the headturn preference procedure, monolingual English‐learning 11‐month‐olds were tested on their ability to segment sentence‐medial vowel‐initial words that followed the function word “the.” First, infants were familiarized with passages containing the target words “ash” and “eff.” Next, infants were presented with two familiar and two novel isolated words. Mean listening time to the familiar and unfamiliar words was significantly different [t(12) = 4.220, p < 0.001]. Out of 13 infants, 12 listened longer to the familiar words compared to the novel words. In experiment 2, monolingual English‐learning 8‐month‐olds are currently being tested using the same task. Preliminary results show three out of five 8‐month‐olds listen longer to the familiar words compared to the novel words.

Discrimination of voicing on the basis of temporal envelope cues in 6-month old infants.

Several studies indicate that profoundly deaf children receiving a cochlear implant (CI) under the age of 2 years are able to develop linguistic skills at a rate equal to similarly aged children with normal hearing. CI devices deliver temporal-envelope (E) cues in speech over a small number of frequency channels. This suggests that infants are able to use efficiently E speech cues at an early age. However, little work has been done to investigate the developmental time course of the ability to use E speech cues. A recent study suggests that normal-hearing children are able to use such cues at adult levels by the age of 5 years, but information is lacking for younger children. The present study assessed the ability of 6-month old infants with normal hearing to discriminate between voiced and unvoiced stop consonants (/aba/ versus /apa/) on the basis of E cues, using a head-turn preference procedure and speech tokens processed via a tone or a noise E vocoder. The spectral and temporal resolutions of vocoders were varied to determine whether or not the ability to use E speech cues is similarly constrained in infants and adults. Preliminary results indicate that this method is applicable to young infants.

Is early word-form processing stress-full? How natural variability supports recognition

In a series of studies, we examined how mothers naturally stress words across multiple mentions in speech to their infants and how this marking influences infants’ recognition of words in fluent speech. We first collected samples of mothers’ infant-directed speech using a technique that induced multiple repetitions of target words. Acoustic analyses revealed that mothers systematically alternated between emphatic and nonemphatic stress when talking to their infants. Using the headturn preference procedure, we then tested 7.5-month-old infants on their ability to detect familiarized bisyllabic words in fluent speech. Stress of target words (emphatic and nonemphatic) was systematically varied across familiarization and recognition phases of four experiments. Results indicated that, although infants generally prefer listening to words produced with emphatic stress, recognition was enhanced when the degree of emphatic stress at familiarization matched the degree of emphatic stress at recognition.

Does the message matter? The effect of song type on infants’ pitch preferences for lullabies and playsongs

Preverbal infants are attuned to the different emotional messages contained in playsongs and lullabies. However, it is unclear which performance properties of singing underlie infants’ perception of the communicative intent of infant-directed singing. Volkova, Trehub, and Schellenberg (2006) recently demonstrated that 6- and 7-month-old infants preferred low-pitched to high-pitched renditions of lullabies, suggesting that pitch may be one performance characteristic that conveys the communicative intent in infant-directed singing. In the current study, we evaluated 6- and 7-month-old infants’ natural preferences for unfamiliar, expressive lullabies and playsongs as a function of pitch using a head-turn preference procedure. Infants preferred low-pitched over high-pitched versions of lullabies and high-pitched over low-pitched versions of playsongs. Results suggest that the overall pitch of a song is communicative to infants and that the affective nature of music can have an effect on infants’ pitch preferences. That is, infants’ preferences for pitch are context-dependent.

Language specific prosodic preferences during the first half year of life: Evidence from German and French infants

There is converging evidence that infants are sensitive to prosodic cues from birth onwards and use this kind of information in their earliest steps into the acquisition of words and syntactic regularities of their target language. Regarding word segmentation, it has been found that English-learning infants segment trochaic words by 7.5 months of age, and iambic words only by 10.5 months of age [Jusczyk, P. W., Houston, D. M., & Newsome, M. (1999). The beginnings of word segmentation in English-learning infants. Cognitive Psychology, 39, 159–207]. The question remains how to interpret this finding in relation to results showing that English-learning infants develop a preference for trochaic over iambic words between 6 and 9 months of age [Jusczyk, P. W., Cutler, A., & Redanz, N. (1993). Preference for the predominant stress patterns of English words. Child Development, 64, 675–687]. In the following, we report the results of four experiments using the headturn preference procedure (HPP) to explore the trochaic bias issue in German- and French-learning infants. For German, a trochaic preference was found at 6 but not at 4 months, suggesting an emergence of this preference between both ages (Experiments 1 and 2). For French, 6-month-old infants did not show a preference for either stress pattern (Experiment 3) while they were found to discriminate between the two stress patterns (Experiment 4). Our findings are the first to demonstrate that the trochaic bias is acquired by 6 months of age, is language specific and can be predicted by the rhythmic properties of the language in acquisition. We discuss the implications of this very early acquisition for our understanding of the emergence of segmentation abilities.

Basic word segmentation abilities emerge earlier in infancy than previously thought.

English‐learning 7.5‐ but not 6‐month‐olds extract word forms from fluent speech (Jusczyk et al., 1999). Thus, English learners are thought to begin segmenting words from speech by 7.5 months. However, recent research has shown that when target words are flanked by a frequent and emotionally salient word (e.g., the infant’s name), even 6‐month‐olds can extract words from speech (e.g., Bortfeld et al., 2005). This suggests that basic word segmentation capabilities may emerge earlier than past studies have suggested. Using the Headturn Preference Procedure, we tested 6‐month‐olds’ ability to segment utterance‐flanked words from speech, e.g., “geff” from “At the circus we met a silly geff.” Infants were familiarized with passages containing target words in utterance initial and final position, and then tested on their recognition of these words in isolation. A significant looking time difference to familiar versus unfamiliar words was found, indicating that 6‐month‐olds segmented the target words from speech. Six‐month‐olds’ success at segmenting utterance‐flanked words from speech is particularly interesting because infant‐directed speech consists of short utterances containing many utterance‐flanked words. Segmentation of utterance‐flanked words could help infants learn the cues needed to extract harder utterance‐medial words from speech (see Seidl and Johnson, 2006).

Voice familiarity helps infants tackle variability in the speech signal.

The acoustic realization of lexical items produced by different speakers can vary greatly. Current research suggests that infants, unlike adults, struggle to cope with this lack of invariance in the realization of words. Although 7.5-month olds are able to recognize words across different utterances when produced by speakers of the same gender with similar voices, they fail to do so when target words produced in a female voice are subsequently produced in a male voice [Houston and Jusczyk (2000)]. Note that all work in this area has used disembodied unfamiliar voices to test infants. In the current study, we ask whether infants might perform better under more ecologically valid conditions, i.e., when tested on familiar rather than unfamiliar voices. Using the headturn preference procedure, infants were familiarized with passages spoken by their mother. During the test phase, they were presented with their father’s voice producing isolated repetitions of familiarized target words. Preliminary results suggest that infants may recognize words across different utterances produced by speakers of different genders if they are highly familiar with both the male and female speakers. In other words, infants may handle variability in the realization of words better when tested on familiar rather than unfamiliar voices.

Melody recognition by two-month-old infants

Music is part of an infant's world even before birth, and caregivers around the world sing to infants. Yet, there has been little research into the musical abilities or preferences of infants younger than 5 months. In this study, the head turn preference procedure used with older infants was adapted into an eye-movement preference procedure so that the ability of 2-month-old infants to remember a short melody could be tested. The results show that with minimal familiarization, 2-month-old infants remember a short melody and can discriminate it from a similar melody.