Object labeling and disambiguation in 4-month-old infants.

The account that word learning starts in earnest during the second year of life, when infants have mastered the disambiguation skills, has recently been challenged by evidence that infants during the first year already know many common words. The preliminary ability to rapidly map and disambiguate linguistic labels was tested in Italian-speaking infants (N = 96, 47 boys; age = 4 and 6 months, eye tracking). Infants can rapidly map linguistic labels to objects and movements, and disambiguate the intended referents to novel words, but they fail with sinewave analogs. In hearing infants, mapping and disambiguation emerge early in development, and are flexible as to which visual referents infants are willing to map to linguistic labels, but may be constrained to linguistic sounds.

Prosody outweighs statistics in 6-month-old German-learning infants' speech segmentation.

It is well established that infants use various cues to find words within fluent speech from about 7 to 8 months of age. Research suggests that two main mechanisms support infants' speech segmentation: prosodic cues like the word stress patterns, and distributional cues like transitional probabilities (TPs). We tested 6-month-old German-learning infants' use of prosodic and statistical cues for speech segmentation in three experiments. In Experiment 1, infants were familiarized with an artificial language string where TPs signaled either word boundaries or iambic words-a stress pattern that is disfavored in German. Experiment 2 was a control and only the test phase was presented. In Experiment 3, prosodic cues were absent in the string and only TPs signaled word boundaries. All experiments included the same conditions at test: disyllabic words with high TPs in the string, words with low TPs and words with non-co-occurring syllables. Results showed that infants relied more strongly on prosodic cues than on TPs for word segmentation. Notably, no segmentation evidence emerged when prosodic cues were absent in the string. This finding underlines early impacts of language-specific structural properties on segmentation mechanisms.

Music and language in the crib: Early cross-domain effects of experience on categorical perception of prominence in spoken language.

Rhythm perception helps young infants find structure in both speech and music. However, it remains unknown whether categorical perception of suprasegmental linguistic rhythm signaled by a co-variation of multiple acoustic cues can be modulated by prior between- (music) and within-domain (language) experience. Here we tested 6-month-old German-learning infants' ability to have a categorical perception of lexical stress, a linguistic prominence signaled through the co-variation of pitch, intensity, and duration. By measuring infants' pupil size, we find that infants as a group fail to perceive co-variation of these acoustic cues as categorical. However, at an individual level, infants with above-average exposure to music and language at home succeeded. Our results suggest that early exposure to music and infant-directed language can boost the categorical perception of prominence. RESEARCH HIGHLIGHTS: 6-month-old German-learning infants' ability to perceive lexical stress prominence categorically depends on exposure to music and language at home. Infants with high exposure to music show categorical perception. Infants with high exposure to infant-directed language show categorical perception. Co-influence of high exposure to music and infant-directed language may be especially beneficial for categorical perception. Early exposure to predictable rhythms boosts categorical perception of prominence.

Transitional probabilities count more than frequency, but might not be used for memorization.

Learners often need to extract recurring items from continuous sequences, in both vision and audition. The best-known example is probably found in word-learning, where listeners have to determine where words start and end in fluent speech. This could be achieved through universal and experience-independent statistical mechanisms, for example by relying on Transitional Probabilities (TPs). Further, these mechanisms might allow learners to store items in memory. However, previous investigations have yielded conflicting evidence as to whether a sensitivity to TPs is diagnostic of the memorization of recurring items. Here, we address this issue in the visual modality. Participants were familiarized with a continuous sequence of visual items (i.e., arbitrary or everyday symbols), and then had to choose between (i) high-TP items that appeared in the sequence, (ii) high-TP items that did not appear in the sequence, and (iii) low-TP items that appeared in the sequence. Items matched in TPs but differing in (chunk) frequency were much harder to discriminate than items differing in TPs (with no significant sensitivity to chunk frequency), and learners preferred unattested high-TP items over attested low-TP items. Contrary to previous claims, these results cannot be explained on the basis of the similarity of the test items. Learners thus weigh within-item TPs higher than the frequency of the chunks, even when the TP differences are relatively subtle. We argue that these results are problematic for distributional clustering mechanisms that analyze continuous sequences, and provide supporting computational results. We suggest that the role of TPs might not be to memorize items per se, but rather to prepare learners to memorize recurring items once they are presented in subsequent learning situations with richer cues.

Co-occurrence statistics as a language-dependent cue for speech segmentation.

To what extent can language acquisition be explained in terms of different associative learning mechanisms? It has been hypothesized that distributional regularities in spoken languages are strong enough to elicit statistical learning about dependencies among speech units. Distributional regularities could be a useful cue for word learning even without rich language-specific knowledge. However, it is not clear how strong and reliable the distributional cues are that humans might use to segment speech. We investigate cross-linguistic viability of different statistical learning strategies by analyzing child-directed speech corpora from nine languages and by modeling possible statistics-based speech segmentations. We show that languages vary as to which statistical segmentation strategies are most successful. The variability of the results can be partially explained by systematic differences between languages, such as rhythmical differences. The results confirm previous findings that different statistical learning strategies are successful in different languages and suggest that infants may have to primarily rely on non-statistical cues when they begin their process of speech segmentation.

Infants show systematic rhythmic motor responses while listening to rhythmic speech.

Rhythm is known to play an important role in infant language acquisition, but few infant language development studies have considered that rhythm is multimodal and shows strong connections between speech and the body. Based on the observation that infants sometimes show rhythmic motor responses when listening to auditory rhythms, the present study asked whether specific rhythm cues (pitch, intensity, or duration) would systematically increase infants' spontaneous rhythmic body movement, and whether their rhythmic movements would be associated with their speech processing abilities. We used pre-existing experimental and video data of 148 German-learning 7.5- and 9.5-month-old infants tested on their use of rhythm as a cue for speech segmentation. The infants were familiarized with an artificial language featuring syllables alternating in pitch, intensity, duration, or none of these cues. Subsequently, they were tested on their recognition of bisyllables based on perceived rhythm. We annotated infants' rhythmic movements in the videos, analyzed whether the rhythmic moving durations depended on the perceived rhythmic cue, and correlated them with the speech segmentation performance. The result was that infants' motor engagement was highest when they heard a duration-based speech rhythm. Moreover, we found an association of the quantity of infants' rhythmic motor responses and speech segmentation. However, contrary to the predictions, infants who exhibited fewer rhythmic movements showed a more mature performance in speech segmentation. In sum, the present study provides initial exploratory evidence that infants' spontaneous rhythmic body movements while listening to rhythmic speech are systematic, and may be linked with their language processing. Moreover, the results highlight the need for considering infants' spontaneous rhythmic body movements as a source of individual differences in infant auditory and speech perception.

In medio stat virtus: theoretical and methodological extremes regarding reciprocity will not explain complex social behaviors.

Guala contests the validity of strong reciprocity as a key element in shaping social behavior by contrasting evidence from experimental games to that of natural and historic data. He suggests that in order to understand the evolution of social behavior researchers should focus on natural data and weak reciprocity. We disagree with Guala's proposal to shift the focus of the study from one extreme of the spectrum (strong reciprocity) to the other extreme (weak reciprocity). We argue that the study of the evolution of social behavior must be comparative in nature, and we point out experimental evidence that shows that social behavior is not cooperation determined by a set of fixed factors. We argue for a model that sees social behavior as a dynamic interaction of genetic and environmental factors.

Pupillary entrainment reveals individual differences in cue weighting in 9-month-old German-learning infants.

Young infants can segment continuous speech with statistical as well as prosodic cues. Understanding how these cues interact can be informative about how infants solve the segmentation problem. Here we investigate how German-speaking adults and 9-month-old German-learning infants weigh statistical and prosodic cues when segmenting continuous speech. We measured participants' pupil size while they were familiarized with a continuous speech stream where prosodic cues were pitted off against transitional probabilities. Adult participants' changes in pupil size synchronized with the occurrence of prosodic words during the familiarization and the temporal alignment of these pupillary changes was predictive of adult participants' performance at test. Further, 9-month-olds as a group failed to consistently segment the familiarization stream with prosodic or statistical cues. However, the variability in temporal alignment of the pupillary changes at word frequency showed that prosodic and statistical cues compete for dominance when segmenting continuous speech. A follow-up language development questionnaire at 40 months of age suggested that infants who entrained to prosodic words performed better on a vocabulary task and those infants who relied more on statistical cues performed better on grammatical tasks. Together these results suggest that statistics and prosody may serve different roles in speech segmentation in infancy.

Object individuation and labelling in 6-month-old infants.

The ability to determine how many objects are involved in physical events is fundamental for reasoning about the world that surrounds us. Previous studies suggest that infants can fail to individuate objects in ambiguous occlusion events until their first birthday and that learning words for the objects may play a crucial role in the development of this ability. The present eye-tracking study tested whether the classical object individuation experiments underestimate young infants' ability to individuate objects and the role word learning plays in this process. Three groups of 6-month-old infants (N = 72) saw two opaque boxes side by side on the eye-tracker screen so that the content of the boxes was not visible. During a familiarization phase, two visually identical objects emerged sequentially from one box and two visually different objects from the other box. For one group of infants the familiarization was silent (Visual Only condition). For a second group of infants the objects were accompanied with nonsense words so that objects' shape and linguistic labels indicated the same number of objects in the two boxes (Visual & Language condition). For the third group of infants, objects' shape and linguistic labels were in conflict (Visual vs. Language condition). Following the familiarization, it was revealed that both boxes contained the same number of objects (e.g. one or two). In the Visual Only condition, infants looked longer to the box with incorrect number of objects at test, showing that they could individuate objects using visual cues alone. In the Visual & Language condition infants showed the same looking pattern. However, in the Visual vs Language condition infants looked longer to the box with incorrect number of objects according to linguistic labels. The results show that infants can individuate objects in a complex object individuation paradigm considerably earlier than previously thought and that linguistic cues enforce their own preference in object individuation. The results are consistent with the idea that when language and visual information are in conflict, language can exert an influence on how young infants reason about the visual world.

Quantifying the role of rhythm in infants' language discrimination abilities: A meta-analysis.

More than 30 years have passed since Mehler et al. (1988) proposed that newborns can discriminate between languages that belong to different rhythm classes: stress-, syllable- or mora-timed. Thereupon they developed the hypothesis that infants are sensitive to differences in vowel and consonant interval durations as acoustic correlates of rhythm classes. It remains unknown exactly which durational computations infants use when perceiving speech for the purposes of distinguishing languages. Here, a meta-analysis of studies on infants' language discrimination skills over the first year of life was conducted, aiming to quantify how language discrimination skills change with age and are modulated by rhythm classes or durational metrics. A systematic literature search identified 42 studies that tested infants' (birth to 12 months) discrimination or preference of two language varieties, by presenting infants with auditory or audio-visual continuous speech. Quantitative data synthesis was conducted using multivariate random effects meta-analytic models with the factors rhythm class difference, age, stimulus manipulation, method, and metrics operationalising proportions of and variability in vowel and consonant interval durations, to explore which factors best account for language discrimination or preference. Results revealed that smaller differences in vowel interval variability (△V) and larger differences in successive consonantal interval variability (rPVI-C) were associated with more successful language discrimination, and better accounted for discrimination results than the factor rhythm class. There were no effects of age for discrimination but results on preference studies were affected by age: the older infants get, the more they prefer non-native languages that are rhythmically similar to their native language, but not non-native languages that are rhythmically distinct. These findings can inform theories on language discrimination that have previously focussed on rhythm class, by providing a novel way to operationalise rhythm in language in the extent to which it accounts for infants' language discrimination abilities.

Cognitive systems struggling for word order.

We argue that the grammatical diversity observed among the world's languages emerges from the struggle between individual cognitive systems trying to impose their preferred structure on human language. We investigate the cognitive bases of the two most common word orders in the world's languages: SOV (Subject-Object-Verb) and SVO. Evidence from language change, grammaticalization, stability of order, and theoretical arguments, indicates a syntactic preference for SVO. The reason for the prominence of SOV languages is not as clear. In two gesture-production experiments and one gesture comprehension experiment, we show that SOV emerges as the preferred constituent configuration in participants whose native languages (Italian and Turkish) have different word orders. We propose that improvised communication does not rely on the computational system of grammar. The results of a fourth experiment, where participants comprehended strings of prosodically flat words in their native language, shows that the computational system of grammar prefers the orthogonal Verb-Object orders.

Rhythm in language acquisition.

Spoken language is governed by rhythm. Linguistic rhythm is hierarchical and the rhythmic hierarchy partially mimics the prosodic as well as the morpho-syntactic hierarchy of spoken language. It can thus provide learners with cues about the structure of the language they are acquiring. We identify three universal levels of linguistic rhythm - the segmental level, the level of the metrical feet and the phonological phrase level - and discuss why primary lexical stress is not rhythmic. We survey experimental evidence on rhythm perception in young infants and native speakers of various languages to determine the properties of linguistic rhythm that are present at birth, those that mature during the first year of life and those that are shaped by the linguistic environment of language learners. We conclude with a discussion of the major gaps in current knowledge on linguistic rhythm and highlight areas of interest for future research that are most likely to yield significant insights into the nature, the perception, and the usefulness of linguistic rhythm.

Rhythm on Your Lips.

The Iambic-Trochaic Law (ITL) accounts for speech rhythm, grouping of sounds as either Iambs-if alternating in duration-or Trochees-if alternating in pitch and/or intensity. The two different rhythms signal word order, one of the basic syntactic properties of language. We investigated the extent to which Iambic and Trochaic phrases could be auditorily and visually recognized, when visual stimuli engage lip reading. Our results show both rhythmic patterns were recognized from both, auditory and visual stimuli, suggesting that speech rhythm has a multimodal representation. We further explored whether participants could match Iambic and Trochaic phrases across the two modalities. We found that participants auditorily familiarized with Trochees, but not with Iambs, were more accurate in recognizing visual targets, while participants visually familiarized with Iambs, but not with Trochees, were more accurate in recognizing auditory targets. The latter results suggest an asymmetric processing of speech rhythm: in auditory domain, the changes in either pitch or intensity are better perceived and represented than changes in duration, while in the visual domain the changes in duration are better processed and represented than changes in pitch, raising important questions about domain general and specialized mechanisms for speech rhythm processing.

Listening natively across perceptual domains?

Our native tongue influences the way we perceive other languages. But does it also determine the way we perceive nonlinguistic sounds? The authors investigated how speakers of Italian, Turkish, and Persian group sequences of syllables, tones, or visual shapes alternating in either frequency or duration. We found strong native listening effects with linguistic stimuli. Speakers of Italian grouped the linguistic stimuli differently from speakers of Turkish and Persian. However, speakers of all languages showed the same perceptual biases when grouping the nonlinguistic auditory and the visual stimuli. The shared perceptual biases appear to be determined by universal grouping principles, and the linguistic differences caused by prosodic differences between the languages. Although previous findings suggest that acquired linguistic knowledge can either enhance or diminish the perception of both linguistic and nonlinguistic auditory stimuli, we found no transfer of native listening effects across auditory domains or perceptual modalities. (PsycINFO Database Record

A new perspective on word order preferences: the availability of a lexicon triggers the use of SVO word order.

Word orders are not distributed equally: SOV and SVO are the most prevalent among the world's languages. While there is a consensus that SOV might be the "default" order in human languages, the factors that trigger the preference for SVO are still a matter of debate. Here we provide a new perspective on word order preferences that emphasizes the role of a lexicon. We propose that while there is a tendency to favor SOV in the case of improvised communication, the exposure to a shared lexicon makes it possible to liberate sufficient cognitive resources to use syntax. Consequently SVO, the more efficient word order to express syntactic relations, emerges. To test this hypothesis, we taught Italian (SVO) and Persian (SOV) speakers a set of gestures and later asked them to describe simple events. Confirming our prediction, results showed that in both groups a consistent use of SVO emerged after acquiring a stable gesture repertoire.

Spontaneous object and movement representations in 4-month-old human infants and albino Swiss mice.

Can young infants decompose visual events into independent representations of objects and movements? Previous studies suggest that human infants may be born with the notion of objects but there is little evidence for movement representations during the first months of life. We devised a novel Rapid Visual Recognition Procedure to test whether the nervous system is innately disposed for the conceptual decomposition of visual events. We show that 4-month-old infants can spontaneously build object and movement representations and recognize these in partially matching test events. Also albino Swiss mice that were tested on a comparable procedure could spontaneously build detailed mental representations of moving objects. Our results dissociate the ability to conceptually decompose physical events into objects and spatio-temporal relations from various types of human and non-human specific experience, and suggest that the nervous system is genetically predisposed to anticipate the representation of objects and movements in both humans and non-human species.

Prosody in the hands of the speaker.

In everyday life, speech is accompanied by gestures. In the present study, two experiments tested the possibility that spontaneous gestures accompanying speech carry prosodic information. Experiment 1 showed that gestures provide prosodic information, as adults are able to perceive the congruency between low-pass filtered-thus unintelligible-speech and the gestures of the speaker. Experiment 2 shows that in the case of ambiguous sentences (i.e., sentences with two alternative meanings depending on their prosody) mismatched prosody and gestures lead participants to choose more often the meaning signaled by gestures. Our results demonstrate that the prosody that characterizes speech is not a modality specific phenomenon: it is also perceived in the spontaneous gestures that accompany speech. We draw the conclusion that spontaneous gestures and speech form a single communication system where the suprasegmental aspects of spoken language are mapped to the motor-programs responsible for the production of both speech sounds and hand gestures.

Mice discriminate between stationary and moving 2D shapes: application to the object recognition task to increase attention.

Selective attention can be assessed with the novel object recognition (NOR) test. In the standard version of this test the selection of objects to be used is critical. We created a modified version of NOR, the virtual object recognition test (VORT) in mice, where the 3D objects were replaced with highly discriminated geometrical shapes and presented on two 3.5-inch widescreen displays. No difference in the discrimination index (from 5min to 96h of inter-trial) was found between NOR and VORT. Scopolamine and mecamylamine decreased the discrimination index. Conversely, the discrimination index increased when nicotine was given to mice. No further improvement in the discrimination index was observed when nicotine was injected in mice presented with highly discriminable shapes. To test the possibility that object movements increased mice's attention in the VORT, different movements were applied to the same geometrical shapes previously presented. Mice were able to distinguish among different movements (horizontal, vertical, oblique). Notably, the shapes previously found not distinguishable when stationary were better discriminated when moving. Collectively, these findings indicate that VORT, based on virtual geometric simple shapes, offers the possibility to obtain rapid information on amnesic/pro-amnestic potential of new drugs. The introduction of motion is a strong cue that makes the task more valuable to study attention.