Headturn Preference Research Articles

Toddlers Activate Lexical Semantic Knowledge in the Absence of Visual Referents: Evidence from Auditory Priming.

Language learners rapidly acquire extensive semantic knowledge, but the development of this knowledge is difficult to study, in part because it is difficult to assess young children's lexical semantic representations. In our studies, we solved this problem by investigating lexical semantic knowledge in 24-month-olds using the Head-turn Preference Procedure. In Experiment 1, looking times to a repeating spoken word stimulus (e.g., kitty-kitty-kitty) were shorter for trials preceded by a semantically related word (e.g., dog-dog-dog) than trials preceded by an unrelated word (e.g., juice-juice-juice). Experiment 2 yielded similar results using a method in which pairs of words were presented on the same trial. The studies provide evidence that young children activate of lexical semantic knowledge, and critically, that they do so in the absence of visual referents or sentence contexts. Auditory lexical priming is a promising technique for studying the development and structure of semantic knowledge in young children.

Experimental methods in studying child language acquisition.

This article reviews the some of the most widely used methods used for studying children's language acquisition including (1) spontaneous/naturalistic, diary, parental report data, (2) production methods (elicited production, repetition/elicited imitation, syntactic priming/weird word order), (3) comprehension methods (act-out, pointing, intermodal preferential looking, looking while listening, conditioned head turn preference procedure, functional neuroimaging) and (4) judgment methods (grammaticality/acceptability judgments, yes-no/truth-value judgments). The review outlines the types of studies and age-groups to which each method is most suited, as well as the advantage and disadvantages of each. We conclude by summarising the particular methodological considerations that apply to each paradigm and to experimental design more generally. These include (1) choosing an age-appropriate task that makes communicative sense (2) motivating children to co-operate, (3) choosing a between-/within-subjects design, (4) the use of novel items (e.g., novel verbs), (5) fillers, (6) blocked, counterbalanced and random presentation, (7) the appropriate number of trials and participants, (8) drop-out rates (9) the importance of control conditions, (10) choosing a sensitive dependent measure (11) classification of responses, and (12) using an appropriate statistical test. WIREs Cogn Sci 2013, 4:149-168. doi: 10.1002/wcs.1215 For further resources related to this article, please visit the WIREs website. The authors declare no conflict of interest.

The Development of Word Stress Processing in French and Spanish Infants

This study focuses on the development of lexical stress perception during the first year of life. Previous research shows that cross-linguistic differences in word stress organization translate into differences in word stress processing from a very early age: At 9 months, Spanish-learning infants, learning a language with variable word stress, can discriminate between segmentally varied nonsense words with initial stress (e.g., níla, túli) and final stress (e.g., lutá, pukí) in a headturn preference procedure. However, French infants, who learn a language with fixed word stress, can only distinguish between initial and final stress when no segmental variability is involved (Skoruppa et al., 2009). The present study investigates the emergence of this cross-linguistic difference. We show that at six months, neither Spanish nor French infants encode stress patterns in the presence of segmental variability (Experiment 1), while both groups succeed in the absence of segmental variability (Experiment 2). Hence, only Spanish infants, who learn a variable stress language, get better at tracking stress patterns in segmentally varied words between the ages of 6 and 9 months. In contrast, all infants seem to be able to discriminate basic stress patterns in the absence of segmental variability during the first nine months of life, regardless of the status of stress in their native language.

A computational model to investigate assumptions in the headturn preference procedure.

In this paper we use a computational model to investigate four assumptions that are tacitly present in interpreting the results of studies on infants' speech processing abilities using the Headturn Preference Procedure (HPP): (1) behavioral differences originate in different processing; (2) processing involves some form of recognition; (3) words are segmented from connected speech; and (4) differences between infants should not affect overall results. In addition, we investigate the impact of two potentially important aspects in the design and execution of the experiments: (a) the specific voices used in the two parts on HPP experiments (familiarization and test) and (b) the experimenter's criterion for what is a sufficient headturn angle. The model is designed to be maximize cognitive plausibility. It takes real speech as input, and it contains a module that converts the output of internal speech processing and recognition into headturns that can yield real-time listening preference measurements. Internal processing is based on distributed episodic representations in combination with a matching procedure based on the assumptions that complex episodes can be decomposed as positive weighted sums of simpler constituents. Model simulations show that the first assumptions hold under two different definitions of recognition. However, explicit segmentation is not necessary to simulate the behaviors observed in infant studies. Differences in attention span between infants can affect the outcomes of an experiment. The same holds for the experimenter's decision criterion. The speakers used in experiments affect outcomes in complex ways that require further investigation. The paper ends with recommendations for future studies using the HPP.

Effects of Prior Phonotactic Knowledge on Infant Word Segmentation: The Case of Nonadjacent Dependencies

In this study, the authors explored whether French-learning infants use nonadjacent phonotactic regularities in their native language, which they learn between the ages of 7 and 10 months, to segment words from fluent speech. Two groups of 20 French-learning infants were tested using the head-turn preference procedure at 10 and 13 months of age. In Experiment 1, infants were familiarized with 2 passages: 1 containing a target word with a frequent nonadjacent phonotactic structure and the other containing a target word with an infrequent nonadjacent phonotactic structure in French. During the test phase, infants were presented with 4 word lists: 2 containing the target words presented during familiarization and 2 other control words with the same phonotactic structure. In Experiment 2, the authors retested infants' ability to segment words with the infrequent phonotactic structure. Ten- and 13-month-olds were able to segment words with the frequent phonotactic structure, but it is only by 13 months, and only under the circumstances of Experiment 2, that infants could segment words with the infrequent phonotactic structure. These results provide new evidence showing that infant word segmentation is influenced by prior nonadjacent phonotactic knowledge.

When do infants begin recognizing familiar words in sentences?

Previous studies have shown that by 11 but not by 10 months infants recognize words that have become familiar from everyday life independently of the experimental setting. This study explored the ability of 10-, 11-, and 12-month-old infants to recognize familiar words in sentential context, without experimental training. The headturn preference procedure was used to contrast passages containing words likely to be familiar to the infants with passages containing words unlikely to have been previously heard. Two stimulus words were inserted near the beginning and end of each of a set of simple sentence frames. The ability to recognize the familiar words within sentences emerged only at 12 months of age. The contrast between segmentation abilities as they emerge as a result of everyday exposure to language, as assessed here, and those abilities as measured in studies in which words are experimentally trained is discussed in terms of memory-based mechanisms.

Experience-dependent emergence of functional asymmetries

Right head-turning preference is assumed to be a developmental default. This motor asymmetry seems to influence the development of other lateralised behaviours—such as handedness—as a consequence of orienting vision towards the right side of the body. To document the role of visual experience in promoting lateralised functions we assessed head-turning preference and handedness in a group of congenitally blind human adults. We found a left-side preference for head turning but a clear right-handedness in the same individuals. This asymmetric relationship suggests that absence of visual experience can alter head-turning preference and that handedness can emerge without visual orientation towards the right side. Our findings shed new light on the role of visual sensory experience in shaping functional asymmetries and suggest that single-gene models and environment alone cannot fully explain the emergence of functional asymmetries in humans.

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.

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.

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.

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.

English-learning infants’ perception of word stress patterns

Adult speakers of different free stress languages (e.g., English, Spanish) differ both in their sensitivity to lexical stress and in their processing of suprasegmental and vowel quality cues to stress. In a head-turn preference experiment with a familiarization phase, both 8-month-old and 12-month-old English-learning infants discriminated between initial stress and final stress among lists of Spanish-spoken disyllabic nonwords that were segmentally varied (e.g. ['nila, 'tuli] vs [lu'ta, pu'ki]). This is evidence that English-learning infants are sensitive to lexical stress patterns, instantiated primarily by suprasegmental cues, during the second half of the first year of life.

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.

Acoustic Markers of Prominence Influence Infants’ and Adults’ Segmentation of Speech Sequences

Two experiments investigated the way acoustic markers of prominence influence the grouping of speech sequences by adults and 7-month-old infants. In the first experiment, adults were familiarized with and asked to memorize sequences of adjacent syllables that alternated in either pitch or duration. During the test phase, participants heard pairs of syllables with constant pitch and duration and were asked whether the syllables had appeared adjacently during familiarization. Adults were better at remembering pairs of syllables that during familiarization had short syllables preceding long syllables, or high-pitched syllables preceding low-pitched syllables. In the second experiment, infants were familiarized and tested with similar stimuli as in the first experiment, and their preference for pairs of syllables was accessed using the head-turn preference paradigm.When familiarized with syllables alternating in pitch, infants showed a preference to listen to pairs of syllables that had high pitch in the first syllable. However, no preference was found when the familiarization stream alternated in duration. It is proposed that these perceptual biases help infants and adults find linguistic units in the continuous speech stream.While the bias for grouping based on pitch appears early in development, biases for durational grouping might rely on more extensive linguistic experience.