These findings provide new evidence that superior temporal gyrus abnormalities may result from genetically mediated developmental deviance reflecting greater susceptibility to schizophrenia. Further studies and follow-up will lead to greater understanding of the role of the superior temporal gyrus in the premorbid vulnerability to schizophrenia.

Everyone perseverates at one time or another, repeating previous behaviors when they are no longer appropriate. Such perseveration often occurs in situations with working memory demands, and the ability to overcome perseveration has been linked to brain regions critical for working memory. Many theories thus explain perseveration in terms of working memory deficits. However, perseveration also occurs in situations without apparent working memory demands, in which the visible environment specifies appropriate behavior. Such findings appear to challenge working memory accounts of perseveration. To evaluate this challenge, a neural network model of a working memory account of perseveration was tested on tasks with visible solutions. With advances in the mechanisms that support working memory, networks became increasingly able to attend to relevant information in the environment. These developments led to improvements in performance on tasks with visible solutions, paralleling the developmental progression observed in infants. The simulations demonstrate how mechanisms of working memory can subserve perseveration and success on tasks with and without obvious memory demands. In both types of tasks, controlled processing occurs through the activation of task-relevant representations, which provide top-down biasing of other processing pathways. More generally, the simulations demonstrate how common mechanisms can support working memory and attention.

The present work examined the discovery of linguistic cues during a word segmentation task. Whereas previous studies have focused on sensitivity to individual cues, this study addresses how individual cues may be used to discover additional, correlated cues. Twenty-four 9-month-old infants were familiarized with a speech stream, in which syllable-level transitional probabilities and an overlapping novel cue served as cues to word boundaries. Infants’ behavior at test indicated they were able to discover the novel cue. Additional experiments showed that infants did not have a preexisting preference for specific test items, and that transitional probability information was necessary to acquire the novel cue. Results suggest one way learners can discover relevant linguistic structure amidst the multiple overlapping properties of natural language.

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Previous work suggests that phonological neighborhood density is a key factor in shaping early lexical acquisition. Such studies have, however, have not considered how semantic neighborhoods may influence word-learning. We studied how phonological and semantic densities affect both comprehension and production of nouns from the Macarthur-Bates Communicative Development Inventory (MCDI). New measures of semantic and phonological densities, along with child-directed word frequency counts were used to predict the percentage of children who know each word at different ages (8 -30 months) as indicated in MCDI lexical norms. Production was predicted by frequency and phonological density at all time points, replicating previous research. Semantic density predicted production only at 30 months. Comprehension norms were predicted by frequency and semantic density, and never by phonological density. Two-and three-way interactions reveal that semantic density may moderate effects in production, while sound density may moderate effects in comprehension.

As complications of pregnancy and birth may be important risk factors for the development of schizophrenia, studying the "roots" of schizophrenia in high-risk offspring may better elucidate the interface between biology, environment, and susceptibility to illness. Using magnetic resonance imaging (MRI), neurobehavioral assessments and obstetric histories, we found several significant correlations between these multiple factors, suggesting that birth complications may be a nonspecific etiopathogenic risk factor for psychopathology in young relatives at risk for schizophrenia.

In this commentary, we question (1) how embodied Thelen et al.'s model is relative to their aims, and (2) how embodied the behavior of children is in particular response systems, relative to how much dynamic systems theory emphasizes this idea. We close with corrections to mischaracterizations of an alternative, neural network perspective on infant behavior.

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