In the context of a national conversation about exclusionary discipline, we conducted a multilevel examination of the relative contributions of infraction, student, and school characteristics to rates of and racial disparities in out-of-school suspension and expulsion. Type of infraction; race, gender, and to a certain extent socioeconomic status at the individual level; and, at the school level, mean school achievement, percentage Black enrollment, and principal perspectives all contributed to the probability of out-of-school suspension or expulsion. For racial disparities, however, school-level variables, including principal perspectives on discipline, appear to be among the strongest predictors. Such a pattern suggests that schools and districts looking to reduce racial and ethnic disparities in discipline would do well to focus on school- and classroom-based interventions.

Analyses of adult semantic networks suggest a learning mechanism involving preferential attachment: A word is more likely to enter the lexicon the more connected the known words to which it is related. We introduce and test two alternative growth principles: preferential acquisition—words enter the lexicon not because they are related to well-connected words, but because they connect well to other words in the learning environment—and the lure of the associates—new words are favored in proportion to their connections with known words. We tested these alternative principles using longitudinal analyses of developing networks of 130 nouns children learn prior to the age of 30 months. We tested both networks with links between words represented by features and networks with links represented by associations. The feature networks did not predict age of acquisition using any growth model. The associative networks grew by preferential acquisition, with the best model incorporating word frequency, number of phonological neighbors, and connectedness of the new word to words in the learning environment, as operationalized by connectedness to words typically acquired by the age of 30 months.

The shared-features that characterize the noun categories that young children learn first are a formative basis of the human category system. To investigate the potential categorical information contained in the features of early-learned nouns, we examine the graph-theoretic properties of noun-feature networks. The networks are built from the overlap of words normatively acquired by children prior to 2 ½ years of age and perceptual and conceptual (functional) features acquired from adult feature generation norms. The resulting networks have small-world structure, indicative of a high degree of feature overlap in local clusters. However, perceptual features—due to their abundance and redundancy—generate networks more robust to feature omissions, while conceptual features are more discriminating and, per feature, offer more categorical information than perceptual features. Using a network specific cluster identification algorithm (the clique percolation method) we also show that shared features among these early learned nouns create higher-order groupings common to adult taxonomic designations. Again, perceptual and conceptual features play distinct roles among different categories, typically with perceptual features being more inclusive and conceptual features being more exclusive of category memberships. The results offer new and testable hypotheses about the role of shared features in human category knowledge.

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Traditional views separate cognitive processes from sensory-motor processes, seeing cognition as amodal, propositional, and compositional, and thus fundamentally different from the processes that underlie perceiving and acting. These were the ideas on which cognitive science was founded 30 years ago. However, advancing discoveries in neuroscience, cognitive neuroscience, and psychology suggests that cognition may be inseparable from processes of perceiving and acting. From this perspective, this study considers the future of cognitive science with respect to the study of cognitive development.

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The sciences of development and learning have been slow to acknowledge that absence of an identifiable experience that relates straightforwardly to a given perceptionaction ability need not mean that experience per se is irrelevant to the emergence of that ability. A recent study reveals that a difference in diet (plain vs. energy rich) leads to a difference in how rats navigate (use of geometry vs. use of features, respectively). It is a good example of how a seemingly unrelated experience (e.g., what the rats eat) can be a non-obvious yet crucial determiner of perception-action modes. We situate this finding in the broader context of the related conceptions of Schneirla's and Lehrman's Developmental Systems Theory, Gottlieb's Probabilistic Epigenesis, and Bolles's Structure of Learning (see article for references). In doing so we highlight that such phenomena may be the norm, both in development and learning, rather than the exception.