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Journal Article 5.1: Wertz, A. E., & Wynn, K. (2014). Selective social learning of plant edibility in 6- and 18-month-old infants. Psychological Science, 25, 874–882.

Learning Objective: 5.1: Discuss the cognitive-developmental perspective on infant reasoning.

Abstract: Recent research underscores the importance of social learning to the development of food preferences. Here, we explore whether social information about edibility—an adult placing something in his or her mouth—can be selectively tied to certain types of entities. Given that humans have relied on gathered plant resources across evolutionary time, and given the costs of trial-and-error learning, we predicted that human infants may possess selective social learning strategies that rapidly identify edible plants. Evidence from studies with 6- and 18-month-olds demonstrated that infants selectively identify plants, over artifacts, as food sources after seeing the same food-relevant social information applied to both object types. These findings are the first evidence for content-specific social learning mechanisms that facilitate the identification of edible plant resources. Evolved learning mechanisms such as these have enabled humans to survive and thrive in varied and changing environments.

Description: This research explores the evolutionary and social learning mechanism of infants’ knowledge of plant edibility, plausibly one type of core knowledge.

Journal Article 5.2: Rose, S. A., Feldman, J. F., & Jankowski, J. J. (2012). Implications of infant cognition for executive functions at age 11. Psychological Science, 23, 1345–1355.

Learning Objective: 5.2: Describe the information processing system in infants.

Abstract: Recent work suggests that executive functions, the cornerstone of higher-level cognitive operations, are driven by basic information processing abilities. Using structural equation modeling, with latent variables, the present study provides the first evidence that this driving force begins in infancy, such that abilities in infancy predict executive functions at age 11. Information processing abilities in three domains (attention, processing speed, and memory) were assessed when participants were infants (7 and 12 months) and toddlers (24 and 36 months) and were used to predict three executive functions (working memory, inhibition, and shifting) when participants were 11 years old. A model relating infant abilities to age-11 executive functions fit well, and accounted for 9% to 19% of the variance in the executive functions. Paths from both Speed and Memory in infancy to age-11 Working Memory were significant, as was the path from Speed in infancy to age-11 Shifting. A model using abilities in toddlerhood as predictors fit similarly. These findings implicate early basic cognitive abilities in the development of executive functions.

Description: This longitudinal investigation finds that basic information processing parameters, such as processing speed, in infants as young as 7 months of age predict executive functioning at age 11. The research supports an information processing approach to cognitive development.

Journal Article 5.3: Labrell, F., van Geert, P., Declercq, C., & Baltarzart, V., et al. (2014). ‘Speaking volumes’: A longitudinal study of lexical and grammatical growth between 17 and 42 months of age. First Language, 34, 97–124.

Learning Objective: 5.3: Summarize the patterns of language development during infancy and toddlerhood.

Abstract: Dynamic analyses of language growth tell us how vocabulary and grammar develop and how the two might be intertwined. Analyses of growth curves between 17 and 42 months, based on longitudinal data for 34 children, revealed interesting patterns of vocabulary and grammatical developments. They showed that these patterns were nonlinear, but with coinciding peaks of growth, suggesting a bilateral relationship between acquisition of vocabulary and grammar. A more detailed analysis of specific components of vocabulary (nouns, verbs, grammatical words) and grammar showed that each followed its own developmental course, but that its growth rates were likely to be negatively or positively correlated with those of other components. For example, a faster rate for acquiring nouns coincided with a slower rate for verbs. Last, an assessment of intra-individual variability in three children showed that mean scores obscure individual profiles Dynamic analyses of language growth tell us how vocabulary and grammar develop and how the two might be intertwined. Analyses of growth curves between 17 and 42 months, based on longitudinal data for 34 children, revealed interesting patterns of vocabulary and grammatical developments. They showed that these patterns were nonlinear, but with coinciding peaks of growth, suggesting a bilateral relationship between acquisition of vocabulary and grammar. A more detailed analysis of specific components of vocabulary (nouns, verbs, grammatical words) and grammar showed that each followed its own developmental course, but that its growth rates were likely to be negatively or positively correlated with those of other components. For example, a faster rate for acquiring nouns coincided with a slower rate for verbs. Last, an assessment of intra-individual variability in three children showed that mean scores obscure individual profiles.

Description: This article drills down into the naming explosion, providing a detailed analysis of the link between vocabulary growth and grammar development between 17 and 42 months. The naming explosion is one of the most notable features of early language development.