Infant perception of audio-visual speech synchrony in familiar and unfamiliar fluent speech

We investigated the effects of linguistic experience and language familiarity on the perception of audio-visual (A-V) synchrony in fluent speech. In Experiment 1, we tested a group of monolingual Spanish- and Catalan-learning 8-month-old infants to a video clip of a person speaking Spanish. Following habituation to the audiovisually synchronous video, infants saw and heard desynchronized clips of the same video where the audio stream now preceded the video stream by 366, 500, or 666 ms. In Experiment 2, monolingual Catalan and Spanish infants were tested with a video clip of a person speaking English. Results indicated that in both experiments, infants detected a 666 and a 500 ms asynchrony. That is, their responsiveness to A-V synchrony was the same regardless of their specific linguistic experience or familiarity with the tested language. Compared to previous results from infant studies with isolated audiovisual syllables, these results show that infants are more sensitive to A-V temporal relations inherent in fluent speech. Furthermore, the absence of a language familiarity effect on the detection of A-V speech asynchrony at eight months of age is consistent with the broad perceptual tuning usually observed in infant response to linguistic input at this age.     

Two are better than one: comparison influences infants' visual recognition memory

Despite a large literature on infants’ memory for visually presented stimuli, the processes underlying visual memory are not well understood. Two studies with 4-month-olds (N = 60) examined the effects of providing opportunities for comparison of items on infants’ memory for those items. Experiment 1 revealed that 4-month-olds failed to show evidence of memory for an item presented during familiarization in a standard task (i.e., when only one item was presented during familiarization). In Experiment 2, infants showed robust memory for one of two different items presented during familiarization. Thus, infants’ memory for the distinctive features of individual items was enhanced when they could compare items.     

Perception of dynamic information for vowels in syllable onsets and offsets

It has been demonstrated using the “silent-center” (SC) syllable paradigm that there is sufficient information in syllable onsets and offsets,taken together, to support accurate identification of vowels spoken in both citation-form syllables and syllables spoken in sentence context. Using edited natural speech stimuli, the present study examined the identification of American English vowels when increasing amounts of syllable onsetsalone or syllable offsetsalone were presented in their original sentence context. The stimuli were /d/-vowel-/d/ syllables spoken in a short carrier sentence by a male speaker. Listeners attempted to identify the vowels in experimental conditions that differed in the number of pitch periods presented and whether the pitch periods were from syllable onsets or syllable off-sets. In general, syllable onsets were more informative than syllable offsets, although neither onsets nor offsets alone specified vowel identity as well as onsets and offsets together (SC syllables). Vowels differed widely in ease of identification; the diphthongized long vowels /e/, /ae/, /o/ were especially difficult to identify from syllable offsets. Identification of vowels as “front” or “back” was accurate, even from short samples of the syllable; however, vowel "height" was quite difficult to determine, again, especially from syllable offsets. The results emphasize the perceptual importance of time-varying acoustic parameters, which are the direct consequence of the articulatory dynamics involved in producing syllables.     

Rapid word learning in 13- and 17-month-olds in a naturalistic two-word procedure: looking versus reaching measures

This study investigated infants’ rapid learning of two novel words using a preferential looking measure compared with a preferential reaching measure. In Experiment 1, 21 13-month-olds and 20 17-month-olds were given 12 novel label exposures (6 per trial) for each of two novel objects. Next, in the label comprehension tests, infants were shown both objects and were asked, “Where’s the [label]?” (looking preference) and then told, “Put the [label] in the basket” (reaching preference). Only the 13-month-olds showed rapid word learning on the looking measure; neither age group showed rapid word learning on the reaching measure. In Experiment 2, the procedure was repeated 24 h later with 10 participants per age group from Experiment 1. After a further 12 labels per object, both age groups now showed robust evidence of rapid word learning, but again only on the looking measure. This is the earliest looking-based evidence of rapid word learning in infants in a well-controlled (i.e., two-word) procedure; our failure to replicate previous reports of rapid word learning in 13-month-olds with a preferential reaching measure may be due to our use of more rigorous controls for object preferences. The superior performance of the younger infants on the looking measure in Experiment 1 was not straightforwardly predicted by existing theoretical accounts of word learning.     

Object labeling influences infant phonetic learning and generalization

Different kinds of speech sounds are used to signify possible word forms in every language. For example, lexical stress is used in Spanish (/‘be.be/, ‘he/she drinks’ versus /be.’be/, ‘baby’), but not in French (/‘be.be/ and /be.’be/ both mean ‘baby’). Infants learn many such native language phonetic contrasts in their first year of life, likely using a number of cues from parental speech input. One such cue could be parents’ object labeling, which can explicitly highlight relevant contrasts. Here we ask whether phonetic learning from object labeling is abstract—that is, if learning can generalize to new phonetic contexts. We investigate this issue in the prosodic domain, as the abstraction of prosodic cues (like lexical stress) has been shown to be particularly difficult. One group of 10-month-old French-learners was given consistent word labels that contrasted on lexical stress (e.g., Object A was labeled /‘ma.bu/, and Object B was labeled /ma.’bu/). Another group of 10-month-olds was given inconsistent word labels (i.e., mixed pairings), and stress discrimination in both groups was measured in a test phase with words made up of new syllables. Infants trained with consistently contrastive labels showed an earlier effect of discrimination compared to infants trained with inconsistent labels. Results indicate that phonetic learning from object labeling can indeed generalize, and suggest one way infants may learn the sound properties of their native language(s).     

Infants' intermodal perception of two levels of temporal structure in natural events

Infants' intermodal perception of two levels of temporal structure uniting the visual and acoustic stimulation from natural, complex events was investigated in four experiments. Films depicting a single object (single, large marble) and a compound object (group of smaller marbles) colliding against a surface in an erratic pattern were presented to infants between 3 and months of age using an intermodal preference and search method. These stimulus events portrayed two levels of invariant temporal structure: (a) temporal synchrony united the sights and sounds of object impact, and (b) temporal microstructure, the internal temporal structure of each impact sound and motion, specified the composition of the object (single vs. compound). Experiment 1 demonstrated that by 6 months infants detected a relation between the audible and visible stimulation from these events when both levels of invariant temporal structure guided their intermodal exploration. Experiment 2 revealed that by 6 months infants detected the bimodal temporal microstructure specifying object composition. They looked predominantly to the film whose natural soundtrack was played even though the motions of objects in both films were synchronized with the soundtrack. Experiment 3 assessed infants' sensitivity to temporal synchrony relations. Two films depicting objects of the same composition were presented while the motions of only one of them was synchronized with the appropriate soundtrack. Both 6-month-olds showed evidence of detecting temporal synchrony relations under some conditions. Experiment 4 examined how temporal synchrony and temporal microstructure interact in directing intermodal exploration. The natural soundtrack to one of the objects was played out-of-synchrony with the motions of both. In contrast with the results of Experiment 2, infants at 6 months showed no evidence of detecting a relationship between the film and its appropriate soundtrack. This suggests that the temporal asynchrony disrupted their detection of the temporal microstructure specifying object composition. Results of these studies support on invariant-detection view of the development of intermodal perception.     

When do infants expect hands to be connected to a person?

A violation-of-expectation paradigm was used to test whether infants infer a person based on the presence of hands alone. Infants were familiarized to a pair of hands that extended out from a curtain to play with a rattle, after which the curtain was opened to reveal either a real person or a mannequin. Infants’ looking at these outcomes was compared with baseline looking at the person and the mannequin. Experiment 1 showed that 9-month-olds looked significantly longer at the mannequin than at the person after familiarization to hands. Experiment 2 ruled out a low-level feature matching interpretation by showing the same looking pattern in 9-month-olds even when the hands were covered with silver gloves. In Experiment 3, 6-month-olds showed no differential looking at the mannequin and person after familiarization to hands. Taken together, these experiments suggest that infants acquire the expectation that hands are connected to a person between 6 and 9 months of age. This finding has implications for how infants’ attribute goals to manual actions.     

Factors affecting infants' manual search for occluded objects and the genesis of object permanence

Two experiments systematically examined factors that influence infants’ manual search for hidden objects (N = 96). Experiment 1 used a new procedure to assess infants’ search for partially versus totally occluded objects. Results showed that 8.75-month-old infants solved partial occlusions by removing the occluder and uncovering the object, but these same infants failed to use this skill on total occlusions. Experiment 2 used sound-producing objects to provide a perceptual clue to the objects’ hidden location. Sound clues significantly increased the success rate on total occlusions for 10-month-olds, but not for 8.75-month-olds. An identity development account is offered for why infants succeed on partial occlusions earlier than total occlusions and why sound helps only the older infants. We propose a mechanism for how infants use object identity as a basis for developing a notion of permanence. Implications are drawn for understanding the dissociation between looking time and search assessments of object permanence.     

塞辅音范畴通达的时间进程：来自语境效应的证据

采用语境效应范式,以汉语听者为被试,在三个实验中考察了塞辅音声学信息和语音信息激活的时间进程。实验1语境刺激是/ta/、/ka/音节和/ta/、/ka/塞音段的声学模拟音,目标刺激是/ta/-/ka/对比连续体,结果发现,塞音声学信息激活没有产生语境效应。实验2语境刺激是/ta/、/ka/音节和/ta/、/ka/塞音段,结果发现塞音语音信息激活产生了显著的对比语境效应。实验3变化塞音段和目标刺激之间的间隔,系统考察塞音范畴通达的时间进程,结果发现,塞音知觉中听觉加工阶段向语音加工阶段的转变约发生于刺激加工后120 ms。实验结果揭示了塞辅音知觉中音位范畴通达的时间进程。     

Infants’ recognition of objects using canonical color

We explored infants’ ability to recognize the canonical colors of daily objects, including two color-specific objects (human face and fruit) and a non-color-specific object (flower), by using a preferential looking technique. A total of 58 infants between 5 and 8 months of age were tested with a stimulus composed of two color pictures of an object placed side by side: a correctly colored picture (e.g., red strawberry) and an inappropriately colored picture (e.g., green-blue strawberry). The results showed that, overall, the 6- to 8-month-olds showed preference for the correctly colored pictures for color-specific objects, whereas they did not show preference for the correctly colored pictures for the non-color-specific object. The 5-month-olds showed no significant preference for the correctly colored pictures for all object conditions. These findings imply that the recognition of canonical color for objects emerges at 6 months of age.     

Ten- and twelve-month-olds' visual anticipation of orientation and size during grasping

The anticipation of two object dimensions during grasping was investigated in 10- and 12-month-olds. We presented objects varying in both orientation and size and analyzed infants’ anticipatory hand configurations. We found in Experiment 1 that nearly all of the 12-month-olds (94%), but less than half of the 10-month-olds (40%), anticipated both dimensions before touching the object. Experiment 2 ruled out the possibility that this behavior resulted from the infants’ inability to anticipate the size of the stimuli. Thus, integrating two object dimensions during reaching seems to be difficult for 10-month-olds. In addition, we found a sequential adjustment when two dimensions were considered: Infants first adjusted the orientation and then the size. The implications of our findings concerning the planning and execution of grasping movements are discussed.     

All parts of an item are not equal: Effects of phonological redundancy on immediate recall

The process of redintegration is thought to use top-down knowledge to repair partly damaged memory traces. We explored redintegration in the immediate recall of lists from a limited pool of partly phonologically redundant pseudowords. In Experiment 1, four kinds of stimuli were created by adding the syllable /ne/ to two-syllable pseudowords, either to the middle (/tepa/ vs. /tenepa/) or to the end (/tepane/), or adding a different syllable to each item (/tepalo/, /vuropi/). The repeated syllable was thought to be available for redintegration. Lists of two-syllable pseudowords were recalled best, items with a redundant end were intermediate, and items with a redundant middle-syllable were as hard as nonredundant three-syllable items. In Experiment 2, the last syllable was predictable from context but not shared between all stimuli, reducing phonological similarity between items. Performance did not differ from the situation with identicallast syllables. In Experiment 3, a shared first syllable had a detrimental effecton memory. An error analysis showed that beneficial redundancy effects were accompanied by harmful similarity effects, impairing memory for nonredundant syllables. The balance between the two effects depended on syllable position.     

How 7-month-olds interpret ambiguous motion events: Category-based reasoning in infancy

This paper investigates the role of static and dynamic attributes for the animate-inanimate distinction in category-based reasoning of 7-month-olds. Three experiments tested infants’ responses to movement events involving an unfamiliar animal and a ball. When either the animal or the ball showed self-initiated irregular movements (Experiment 1), infants expected the previously active object to start moving again. When both objects were moving together in an ambiguous motion event (Experiment 2), infants expected only the animal to start moving again. Initial looking preferences for each object did not influence results. When either the facial features of the animal were removed, or its furry body was replaced by a plastic spiral in an ambiguous motion event (Experiment 3), infants formed no clear expectation regarding future movements. Based on this set of findings we conclude that 7-month-olds flexibly combine information about the static and dynamic properties of objects in order to reason about motion events.     

Perception of tones by infants learning a non-tone language

This article examines the perception of tones by non-tone-language-learning (non-tone-learning) infants between 5 and 18 months in a study that reveals infants’ initial sensitivity to tonal contrasts, deterioration yet plasticity of tonal sensitivity at the end of the first year, and a perceptual rebound in the second year. Dutch infants in five age groups were tested on their ability to discriminate a tonal contrast of Mandarin Chinese as well as a contracted tonal contrast. Infants are able to discriminate tonal contrasts at 5–6 months, and their tonal sensitivity deteriorates at around 9 months. However, the sensitivity rebound sat 17–18 months. Non-tone-learning infants’ tonal perception is elastic, as is shown by the influence of acoustic salience and distributional learning: (1) a salient contrast may remain discriminable throughout infancy whereas a less salient one does not; (2) a bimodal distribution in tonal exposure increases non-tone-learning infants’ discrimination ability during the trough in sensitivity to tonal contrasts at 11–12 months. These novel findings reveal non-tone-learning infants’ U-shaped pattern in tone perception, and display their perceptual flexibility.     

Learning about occlusion: initial assumptions and rapid adjustments

We examined 6-month-olds abilities to represent occluded objects, using a corneal-reflection eye-tracking technique. Experiment 1 compared infants' ability to extrapolate the current pre-occlusion trajectory with their ability to base predictions on recent experiences of novel object motions. In the first condition infants performed at asymptote ( approximately 2/3 accurate predictions) from the first occlusion passage. In the second condition all infants initially failed to make accurate prediction. Performance, however, reached asymptote after two occlusion passages. This is the first study that demonstrates such rapid learning effects during an occlusion task. Experiment 2 replicates these effects and demonstrates a robust memory effect extending 24h. In occlusion tasks such long-term memory effects have previously only been observed in 14-month-olds (Moore & Meltzoff, 2004).     

Perception of dynamic information for vowels in syllable onsets and offsets.

It has been demonstrated using the "silent-center" (SC) syllable paradigm that there is sufficient information in syllable onsets and offsets, taken together, to support accurate identification of vowels spoken in both citation-form syllables and syllables spoken in sentence context. Using edited natural speech stimuli, the present study examined the identification of American English vowels when increasing amounts of syllable onsets alone or syllable offsets alone were presented in their original sentence context. The stimuli were /d/-vowel-/d/ syllables spoken in a short carrier sentence by a male speaker. Listeners attempted to identify the vowels in experimental conditions that differed in the number of pitch periods presented and whether the pitch periods were from syllable onsets or syllable offsets. In general, syllable onsets were more informative than syllable offsets, although neither onsets nor offsets alone specified vowel identity as well as onsets and offsets together (SC syllables). Vowels differed widely in ease of identification; the diphthongized long vowels /e/, /ae/, /o/ were especially difficult to identify from syllable offsets. Identification of vowels as "front" or "back" was accurate, even from short samples of the syllable; however, vowel "height" was quite difficult to determine, again, especially from syllable offsets. The results emphasize the perceptual importance of time-varying acoustic parameters, which are the direct consequence of the articulatory dynamics involved in producing syllables.     

声调在汉语音节感知中的作用

探讨超音段(如声调)与音段信息的共同作用机制, 对口语词汇识别研究具有重要的理论意义。有研究探讨了声调在口语词汇语义通达阶段的作用, 但在相对早期的音节感知阶段, 声调与声母、韵母的共同作用机制还缺乏系统的认识。本研究采用oddball实验范式, 通过两个行为实验考察了声调在汉语音节感知中的作用。实验1发现检测声调和声母变化的时间没有差异, 均比检测韵母变化的时间长, 表明在汉语音节感知中对声调的敏感性不及韵母。实验2发现声母和韵母的组合并没有明显优于对韵母的觉察, 但声调与声母或韵母的同时变化都促进了被试对偏差刺激的觉察, 表明声调通过与声母、韵母的结合来共同影响汉语音节的感知加工。研究结果在认知行为层面为声调在音节感知中的作用机制提供了直接的实验证据, 为进一步探讨超音段与音段信息共同作用的认知神经机制提供了基础。     

Exogenous attention differentially modulates the processing of categorical and coordinate spatial relations

Carrasco and her colleagues have suggested that exogenous attention reduces the size of receptive fields at an attended location (Gobell & Carrasco, 2005; Yeshurun & Carrasco, 1998, 2000). Based on the hypothesis that categorical and coordinate spatial relations are more efficiently processed by smaller and larger receptive fields, respectively, we predicted that exogenous attention would be more beneficial to the processing of categorical spatial relations than coordinate spatial relations while it would disrupt the processing of coordinate spatial relations. To test these hypotheses, participants were tested using a variant of Posner's (1980) attentional cueing paradigm. Exogenous attention produced larger facilitative effects on categorical spatial processing than on coordinate spatial processing at a short cue-target stimulus onset asynchrony (100 ms, Experiment 1, N = 28), and this result was replicated regardless of cue size in Experiment 2 (N = 24). When the coordinate judgment was sufficiently difficult, exogenous attention disrupted the processing of coordinate spatial relations (Experiment 3, N = 28). These findings indicate that exogenous attention can differentially modulate the processing of categorical and coordinate spatial relations.     

Learning how actions function: the role of outcomes in infants' representation of events

Action is a fundamental component of object representations. However, little is known about how infants represent actions performed on objects. Across four experiments, we tested the hypothesis that at 10 months of age (N = 80) infants represent the general ability of actions to produce outcomes (sounds). Experiments 1A and 1B showed that infants encode actions and associate actions and object appearances in events in which actions produced no sound outcomes. Experiment 2 showed that infants associate the presence or absence of outcomes with actions. Experiment 3 showed, in contrast, that infants did not associate the presence or absence of outcomes with object appearances. Together, these studies suggest that infants encode the outcome potential of specific actions. We discuss the implications of these findings for our understanding of the development of action representations.