Answer to Question 1
Arguably, sleep is the primary activity of the brain during the early years of development. Consider this: By 2 years of age the average child has spent almost 10,000 hours (nearly 14 months) asleep, and approximately 7,500 hours (about 10 months) in waking activities (Anders, Goodlin-Jones, & Sadeh, 2000). During those 2 years, the brain has reached 90 of its adult size and the child has attained remarkable complexity in cognitive skills, language, concept of self, socioemotional development, and physical skills (Dahl, 2007; Dahl & El-Sheikh, 2007). And most of these maturational advances occurred while the child was asleep.
Answer to Question 2
Sleep problems may cause emotional and behavioral problems among children and adolescents, and they may be caused by a psychological disorder. An underlying factor common to both sleep problems and other disorders may cause sleep issues in some cases.
Problems in the brain's arousal and regulatory systems can cause increased anxiety and can affect sleep (see Chapter 11). Stress-related events, especially those that affect the child's safetysuch as war, disaster, and family conflictboth increase arousal and interfere with normal sleep patterns (El-Sheikh, Bub, et al., 2013; Kelly & El-Sheikh, 2013). Simply stated, sleepwake disorders can cause other psychological problems or they can result from other disorders or conditions. Sleepwake disorders have considerable importance to abnormal child psychology because they mimic or worsen many of the symptoms of major disorders.
The Upper Cave at Zhoukoudian yields ages of about 25,000 years for Homo sapiens.
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VESPR Chart. My favorite for many years
Early 20th century warming
Development of Morality in Young Children
Ichthyostega, Early Amphibian