ated directly by standard IQ tests. These include children's regulatory and attentional capacities, certain aspects of memory, and abilities that relate to theory of mind. Moreover, as researchers have learned more about what can go wrong with cognitive development, it becomes imperative to assess the specific dimensions of early cognitive functioning that can reveal serious problems and register the effects of efforts to intervene. For example, understanding of others' intentions and mental states seems to be a quite separate intellectual domain, which is impaired in autism but spared in Down syndrome. Children with autism also display failures to engage in protodeclarative pointing, low rates of direct eye contact with others, low levels of pretend play, language delays, and deficits in reasoning about others' mental states (Baron-Cohen, 1995; Tager-Flusberg, 1989). The research on early biological insults, reviewed in Chapter 8, further calls attention to the importance of assessing the attention, memory, and abstract thinking abilities that appear to be affected by a number of these insults, as well as by prolonged exposure to stress. These are not the outcomes that are typically measured in research on early intervention, despite their relevance to the populations that are typically targeted by these initiatives.

SUMMARY AND CONCLUSIONS

The years from birth to school entry mark a period of remarkable linguistic and intellectual growth. Children make the transition from having no language at all to understanding and expressing the subtleties of intentionality, cause and effect, and emotional states. The motivation and capacity of the newborn to act on and learn about the surrounding world and the people in it flourish during the early childhood years and ultimately transform the newborn into a 5-year-old who is usually well prepared to embark on the formal school curriculum. At the same time, there is no evidence to confirm or disconfirm that the age of 3 or 5 marks the end of a sensitive period in human cognition and, with respect to language development, evidence for sensitive periods is largely restricted to pronunciation and the complex morphological properties of language. In fact, both language development and early learning appear to be relatively resilient processes, largely protected from adverse circumstances and quick to recover when these circumstances are removed, and to be characterized by lifelong capacities for growth and learning.

Nevertheless, some critical aspects of language and learning remain vulnerable to environmental variation even within the normal range that encompasses families at different socioeconomic levels in society. Indeed, evidence reviewed in Part III, suggests that young children's academic attainments may be even more susceptible to the negative influence of poverty than is the case for older children (at least up to adolescence). These less



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