Headturn Preference Procedure Research Articles

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.

Infants' sensitivity to phonotactic regularities related to perceptually low-salient fricatives: a cross-linguistic study.

Infants' sensitivity to language-specific phonotactic regularities emerges between 6- and 9- months of age, and this sensitivity has been shown to impact other early processes such as wordform segmentation and word learning. However, the acquisition of phonotactic regularities involving perceptually low-salient phonemes (i.e., phoneme contrasts that are hard to discriminate at an early age), has rarely been studied and prior results show mixed findings. Here, we aimed to further assess infants' acquisition of such regularities, by focusing on the low-salient contrast of /s/- and /ʃ/-initial consonant clusters. Using the headturn preference procedure, we assessed whether French- and German-learning 9-month-old infants are sensitive to language-specific regularities varying in frequency within and between the two languages (i.e., /st/ and /sp/ frequent in French, but infrequent in German, /ʃt/ and /ʃp/ frequent in German, but infrequent in French). French-learning infants preferred the frequent over the infrequent phonotactic regularities, but the results for the German-learning infants were less clear. These results suggest crosslinguistic acquisition patterns, although an exploratory direct comparison of the French- and German-learning groups was inconclusive, possibly linked to low statistical power to detect such differences. Nevertheless, our findings suggest that infants' early phonotactic sensitivities extend to regularities involving perceptually low-salient phoneme contrasts at 9 months, and highlight the importance of conducting cross-linguistic research on such language-specific processes.

Infants’ short-term memory for consonant–vowel syllables

This research examined whether the auditory short-term memory (STM) capacity for speech sounds differs from that for nonlinguistic sounds in 11-month-old infants. Infants were presented with streams composed of repeating sequences of either 2 or 4 syllables, akin to prior work by Ross-Sheehy and Newman (2015) using nonlinguistic musical instruments. These syllable sequences either stayed the same for every repetition (constant) or changed by one syllable each time it repeated (varying). Using the head-turn preference procedure, we measured infant listening time to each type of stream (constant vs varying and 2 vs 4 syllables). Longer listening to the varying stream was taken as evidence for STM because this required remembering all syllables in the sequence. We found that infants listened longer to the varying streams for 2-syllable sequences but not for 4-syllable sequences. This capacity limitation is comparable to that found previously for nonlinguistic instrument tones, suggesting that young infants have similar STM limitations for speech and nonspeech stimuli.

Early recognition of familiar word-forms as a function of production skills.

Growing evidence shows that early speech processing relies on information extracted from speech production. In particular, production skills are linked to word-form processing, as more advanced producers prefer listening to pseudowords containing consonants they do not yet produce. However, it is unclear whether production affects word-form encoding (the translation of perceived phonological information into a memory trace) and/or recognition (the automatic retrieval of a stored item). Distinguishing recognition from encoding makes it possible to explore whether sensorimotor information is stored in long-term phonological representations (and thus, retrieved during recognition) or is processed when encoding a new item, but not necessarily when retrieving a stored item. In this study, we asked whether speech-related sensorimotor information is retained in long-term representations of word-forms. To this aim, we tested the effect of production on the recognition of ecologically learned, real familiar word-forms. Testing these items allowed to assess the effect of sensorimotor information in a context in which encoding did not happen during testing itself. Two groups of French-learning monolinguals (11- and 14-month-olds) participated in the study. Using the Headturn Preference Procedure, each group heard two lists, each containing 10 familiar word-forms composed of either early-learned consonants (commonly produced by French-learners at these ages) or late-learned consonants (more rarely produced at these ages). We hypothesized differences in listening preferences as a function of word-list and/or production skills. At both 11 and 14 months, babbling skills modulated orientation times to the word-lists containing late-learned consonants. This specific effect establishes that speech production impacts familiar word-form recognition by 11 months, suggesting that sensorimotor information is retained in long-term word-form representations and accessed during word-form processing.

Tracking the associative boost in infancy.

Do words that are both associatively and taxonomically related prime each other in the infant mental lexicon? We explore the impact of these semantic relations in the emerging lexicon. Using the head-turn preference procedure, we show that 18-month-old infants have begun to construct a semantic network of associatively and taxonomically related words, such as dog-cat or apple-cheese. We demonstrate that priming between words is longer-lasting when the relationship is both taxonomic and associative, as opposed to purely taxonomic, reflecting the associative boost reported in the adult priming literature. Our results demonstrate that 18-month-old infants are able to construct a lexical-semantic network based on associative and taxonomic relations between words in the network, and that lexical-semantic links are more robust when they are both associative and taxonomic in character. Furthermore, the manner in which activation is propagated through the emerging lexical-semantic network appears to depend upon the type of semantic relation between words. We argue that 18-month-old infants have a mental lexicon that shares important structural and processing properties with that of the adult system.

Language preference in the domestic dog (Canis familiaris).

Studies have shown that both cotton-top tamarins as well as rats can discriminate between two languages based on rhythmic cues. This is similar to the capabilities of young infants, who also rely on rhythmic cues to differentiate between languages. However, the animals in these studies did not have long-term language exposure, so these studies did not specifically assess the role of language experience. In this study, we used companion dogs, who have prolonged exposure to human language in their home environment. These dogs came from homes where either English or Spanish was primarily spoken. The dogs were then presented with speech in English and in Spanish in a Headturn Preference Procedure paradigm to examine their language discrimination abilities as well as their language preferences. Dogs successfully discriminated between the two languages. In addition, dogs showed a novelty effect with their language preference such that Spanish-hearing dogs listened longer to English, and English-hearing dogs listened longer to Spanish. It is unclear what particular cue dogs are utilizing to discriminate between the two languages; future studies should explore dogs' utilization of phonological and rhythmic cues for language discrimination.

Testing prosodic development with the Headturn Preference Procedure: A test‐retest reliability study

AbstractThe Headturn Preference Procedure (HPP) is widely used in infant research. Previous studies have shown that speech perception measures obtained with HPP are related to later language skills which may make them a potential instrument for an early detection of developmental language risks. The present study assessed the reliability and stability of this measure by testing 6‐month‐old German‐learning infants with the HPP in three sessions each separated by 1 week. Significant correlations were found between the overall looking times across test sessions but not between the differences in looking times for different test conditions. The results underline limitations but also the potential of using early speech perception measures as diagnostic tools.

Spanish input accelerates bilingual infants' segmentation of English words

We asked whether increased exposure to iambs, two-syllable words with stress on the second syllable (e.g., guitar), by way of another language – Spanish – facilitates English learning infants' segmentation of iambs. Spanish has twice as many iambic words (40%) compared to English (20%). Using the Headturn Preference Procedure we tested bilingual Spanish and English learning 8-month-olds' ability to segment English iambs. Monolingual English learning infants succeed at this task only by 11 months. We showed that at 8 months, bilingual Spanish and English learning infants successfully segmented English iambs, and not simply the stressed syllable, unlike their monolingual English learning peers. At the same age, bilingual infants failed to segment Spanish iambs, just like their monolingual Spanish peers. These results cannot be explained by bilingual infants' reliance on transitional probability cues to segment words in both their native languages because statistical cues were comparable in the two languages. Instead, based on their accelerated development, we argue for autonomous but interdependent development of the two languages of bilingual infants.

Fine-tuning language discrimination: Bilingual and monolingual infants' detection of language switching.

The ability to differentiate between two languages sets the stage for bilingual learning. Infants can discriminate languages when hearing long passages, but language switches often occur on short time scales with few cues to language identity. As bilingual infants begin learning sequences of sounds and words, how do they detect the dynamics of two languages? In two studies using the head-turn preference procedure, we investigated whether infants (n=44) can discriminate languages at the level of individual words. In Study 1, bilingual and monolingual 8- to 12-month-olds were tested on their detection of single-word language switching in lists of words (e.g., "dog… lait [fr. milk]"). In Study 2, they were tested on language switching within sentences (e.g., "Do you like the lait?"). We found that infants were unable to detect language switching in lists of words, but the results were inconclusive about infants' ability to detect language switching within sentences. No differences were observed between bilinguals and monolinguals. Given that bilingual proficiency eventually requires detection of sound sequences across two languages, more research will be needed to conclusively understand when and how this skill emerges. Materials, data, and analysis scripts are available at https://osf.io/9dtwn/.

Introducing BITTSy: The Behavioral Infant & Toddler Testing System.

This manuscript introduces BITTSy, the Behavioral Infant & Toddler Testing System. This software system is capable of running the headturn preference procedure, preferential looking, conditioned headturn, and visual fixation/habituation procedures. It uses only commercial-off-theshelf (COTS) hardware to implement the procedures in an affordable and space-efficient setup. The software package, example protocols and data sets, and manual are freely available and downloadable from go.umd.edu/BITTSy, making this entire set of procedures available to resource-limited labs. Researchers can easily use BITTSy at multiple sites in a uniform manner, resulting in a standardized, powerful research tool that can enhance cross-site research collaborations.

Experience with research paradigms relates to infants' direction of preference.

Interpreting and predicting direction of preference in infant research has been a thorny issue for decades. Several factors have been proposed to account for familiarity versus novelty preferences, including age, length of exposure, and task complexity. The current study explores an additional dimension: experience with the experimental paradigm. We reanalyzed the data from 4 experiments on artificial grammar learning in 12-month-old infants run using the head-turn preference procedure (HPP). Participants in these studies varied substantially in their number of laboratory visits. Results show that the number of HPP studies is related to direction of preference: Infants with limited experience with the HPP setting were more likely to show familiarity preferences than infants who had amassed more experience with this paradigm. This evidence has important implications for the interpretation of experimental results: Experience with a given method or, more broadly, with the laboratory environment may affect infants' patterns of preferences.

Six-month-old infants recognize phrases in song and speech.

Infants exploit acoustic boundaries to perceptually organize phrases in speech. This prosodic parsing ability is well-attested and is a cornerstone to the development of speech perception and grammar. However, infants also receive linguistic input in child songs. This study provides evidence that infants parse songs into meaningful phrasal units and replicates previous research for speech. Six-month-old Dutch infants (n=80) were tested in the song or speech modality in the head-turn preference procedure. First, infants were familiarized to two versions of the same word sequence: One version represented a well-formed unit, and the other contained a phrase boundary halfway through. At test, infants were presented two passages, each containing one version of the familiarized sequence. The results for speech replicated the previously observed preference for the passage containing the well-formed sequence, but only in a more fine-grained analysis. The preference for well-formed phrases was also observed in the song modality, indicating that infants recognize phrase structure in song. There were acoustic differences between stimuli of the current and previous studies, suggesting that infants are flexible in their processing of boundary cues while also providing a possible explanation for differences in effect sizes.

Contrasting behavioral looking procedures: a case study on infant speech segmentation

This paper compared three different procedures common in infant speech perception research: a headturn preference procedure (HPP) and a central-fixation (CF) procedure with either automated eye-tracking (CF-ET) or manual coding (CF-M). In theory, such procedures all measure the same underlying speech perception and learning mechanisms and the choice between them should ideally be irrelevant in unveiling infant preference. However, the ManyBabies study (ManyBabies Consortium, 2019), a cross-laboratory collaboration on infants’ preference for child-directed speech, revealed that choice of procedure can modulate effect sizes. Here we examined whether procedure also modulates preference in paradigms that add a learning phase prior to test: a speech segmentation paradigm. Such paradigms are particularly important for studying the learning mechanisms infants can employ for language acquisition. We carried out the same familiarization-then-test experiment with the three different procedures (32 unique infants per procedure). Procedures were compared on various factors, such as overall effect, average looking time and drop-out rate. The key observations are that the HPP yielded a larger familiarity preference, but also reported larger drop-out rates. This raises questions about the generalizability of results. We argue that more collaborative research into different procedures in infant preference experiments is required in order to interpret the variation in infant preferences more accurately.

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.

Perception of sibilant-liquid phonotactic frequency in full-term and preterm infants.

We examined full-term and preterm infants' perception of frequent and infrequent phonotactic pairings involving sibilants and liquids. Infants were tested on their preference for syllables with onsets involving /s/ or /ʃ/ followed by /l/ or /r/ using the Headturn Preference Procedure. Full-term infants preferred the frequent to the infrequent phonotactic pairings at 9 months, but not at either younger or older ages. Evidence was inconclusive regarding a possible difference between full-term and preterm samples; however, limitations on the preterm sample size limited our power to detect differences. Preference for the frequent pairing was not related to later vocabulary development.

Finding phrases: On the role of co-verbal facial information in learning word order in infancy.

The input contains perceptually available cues, which might allow young infants to discover abstract properties of the target language. Thus, word frequency and prosodic prominence correlate systematically with basic word order in natural languages. Prelexical infants are sensitive to these frequency-based and prosodic cues, and use them to parse new input into phrases that follow the order characteristic of their native languages. Importantly, young infants readily integrate auditory and visual facial information while processing language. Here, we ask whether co-verbal visual information provided by talking faces also helps prelexical infants learn the word order of their native language in addition to word frequency and prosodic prominence. We created two structurally ambiguous artificial languages containing head nods produced by an animated avatar, aligned or misaligned with the frequency-based and prosodic information. During 4 minutes, two groups of 4- and 8-month-old infants were familiarized with the artificial language containing aligned auditory and visual cues, while two further groups were exposed to the misaligned language. Using a modified Headturn Preference Procedure, we tested infants’ preference for test items exhibiting the word order of the native language, French, vs. the opposite word order. At 4 months, infants had no preference, suggesting that 4-month-olds were not able to integrate the three available cues, or had not yet built a representation of word order. By contrast, 8-month-olds showed no preference when auditory and visual cues were aligned and a preference for the native word order when visual cues were misaligned. These results imply that infants at this age start to integrate the co-verbal visual and auditory cues.

Towards Abstract Syntax at 24 Months: Evidence from Subject-Verb Agreement with Conjoined Subjects

ABSTRACTWe examined French-learning toddlers’ sensitivity to Subject-Verb agreement with conjoined subjects. In French, a conjoined NP triggers plural agreement even when made up of individual singular NPs. Processing of this infrequent structure in the input (see Corpus Analyses) requires going beyond surface patterns of non-adjacent dependencies to abstract, feature-based syntactic knowledge. In Experiment 1, results revealed a significant grammaticality effect in 24-month-olds, but not in 18-month-olds, with no interaction with the condition (with either conjoined or non-conjoined agreement; all tested with Head-Turn Preference Procedure). In Experiment 2, 30-month-olds (tested with conjoined agreement only) showed the same pattern as 24-month-olds: a strong grammaticality effect limited to the first half of the experiment. Overall, these results provide some support to the hypothesis that 24- and 30-month-olds (but not 18-month-olds) have abstract knowledge of SV agreement with conjoined subjects, although it imposes a high processing cost. Importantly, this abstract syntactic sensitivity precedes the earliest evidence of simple agreement comprehension.

Learning and generalizing non-adjacent dependencies in 18-month-olds: A mechanism for language acquisition?

The ability to track non-adjacent dependencies (the relationship between ai and bi in an aiXbi string) has been hypothesized to support detection of morpho-syntactic dependencies in natural languages (‘The princess is reluctantly kissing the frog’). But tracking such dependencies in natural languages entails being able to generalize dependencies to novel contexts (‘The general is angrily berating his troops’), and also tracking co-occurrence patterns between functional morphemes like is and ing (a class of elements that often lack perceptual salience). We use the Headturn Preference Procedure to investigate (i) whether infants are capable of generalizing dependencies to novel contexts, and (ii) whether they can track dependencies between perceptually non-salient elements in an artificial grammar aXb. Results suggest that 18-month-olds extract abstract knowledge of a_b dependencies between non-salient a and b elements and use this knowledge to subsequently re-familiarize themselves with specific ai_bi combinations. However, they show no evidence of generalizing ai_bi dependencies to novel aiYbi strings.

Lexical stress constrains English-learning infants’ segmentation in a non-native language

Infants’ ability to segment words in fluent speech is affected by their language experience. In this study we investigated the conditions under which infants can segment words in a non-native language. Using the Head-turn Preference Procedure, we found that monolingual English-learning 8-month-olds can segment bisyllabic words in Spanish (trochees and iambs) but not French (iambs). Our results are incompatible with accounts that rely on distributional learning, language rhythm similarity, or target word prosodic shape alone. Instead, we show that monolingual English-learning infants are able to segment words in a non-native language as long as words have stress, as is the case in English. More specifically, we show that even in a rhythmically different non-native language, English-learning infants can find words by detecting stressed syllables and treating them as word onsets or offsets.

Infants’ sensitivity to rhyme in songs

Children’s songs often contain rhyming words at phrase endings. In this study, we investigated whether infants can already recognize this phonological pattern in songs. Earlier studies using lists of spoken words were equivocal on infants’ spontaneous processing of rhymes (Hayes et al., 2000; Jusczyk et al., 1999). Songs, however, constitute an ecologically valid rhyming stimulus, which could allow for spontaneous processing of this phonological pattern in infants. Novel children’s songs with rhyming and non-rhyming lyrics using pseudo-words were presented to 35 9-month-old Dutch infants using the Headturn Preference Procedure. Infants on average listened longer to the non-rhyming songs, with around half of the infants however exhibiting a preference for the rhyming songs. These results highlight that infants have the processing abilities to benefit from their natural rhyming input for the development of their phonological abilities.