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BackgroundPrevious studies have explored the effects of familiarity on various kinds of visual face judgments, yet the role of familiarity in face processing is not fully understood. Across different face judgments and stimulus sets, the data is equivocal as to whether or not familiarity impacts recognition processes.Methodology/Principal FindingsHere, we examine the effect of real-world personal familiarity in three simple delayed-match-to-sample tasks in which subjects were required to match faces on the basis of orientation (upright v. inverted), gender and identity. We find that subjects had a significant speed advantage with familiar faces in all three tasks, with large effects for the gender and identity matching tasks.Conclusion/SignificanceOur data indicates that real-world experience with a face exerts a powerful influence on face processing in tasks where identity information is irrelevant, even in tasks that could in principle be solved via low-level cues. These results underscore the importance of experience in shaping visual recognition processes.

This study examines 16-month-olds' understanding of word order and inflectional properties of familiar nouns and verbs. Infants preferred grammatical sentences over ungrammatical sentences when the ungrammaticality was cued by both misplaced inflection and word order reversal of nouns and verbs. Infants were also sensitive to inflection alone as a cue to grammaticality, but not word order alone. The preference for grammatical sentence forms was also disrupted when adjacent function word cues were removed from the stimuli, and when familiar content words were replaced by nonce words. These results suggest that sensitivity to the relationship between functional morphemes and content words, rather than sensitivity to either independently, drives the development of early grammatical knowledge. Furthermore, infants showed some ability to generalize from familiar to nonce content word contexts.Although languages vary greatly in their surface form, traditional linguistic theory suggests that similar types of underlying structural or syntactic principles govern all languages. The task of the language learner is to infer the underlying syntactic principles governing the target language based on observations of the surface form of the linguistic input. Setting aside important differences in phonological and lexical properties, languages manifest this underlying structure in two main ways: the order in which words appear, and the inflectional endings on words. Languages like English rely heavily on word order in determining how words relate to one another in a sentence (e.g., third singular verbal inflection or a plural noun inflection), also plays a role in English, although to a lesser extent than in languages like Russian or German, which have case marking and noun-adjective agreement. English is relatively impoverished in its inflectional properties, but those inflections that do appear still contribute information about the syntactic structure of a sentence. The primary focus of this article is to examine the development of infants' understanding of the word order and inflectional properties of English. SYNTACTIC CATEGORIESDifferent categories of words, by definition, exhibit different syntactic behavior. Therefore, to acquire both the word order and inflectional systems, infants must be able to group words into different categories with different properties. At the highest level, infants must group words into content words, like nouns and verbs, which bear the larger semantic load and have a small tokedtype ratio, and function words (e.g., the, is, she), which are more structural in nature and have a high tokedtype ratio. There is evidence that infants can perceptually distinguish content and function words from very early on (Shi, Werker, &Morgan, 1999). These categories are further subdivided: function words into determiners, auxiliaries and pronouns, and so on, and content words into classes like noun and verb. At some point, learners must be able to distinguish these finer categories as well.There is currently a d...