Middle childhood, between 7 and 11 years old, is a period that some theorists, such as Freud and Piaget, regarded as a plateau stage of development. Others, including Eriksson, considered this period of development important, as it is when children have a greater exposure to different social contexts and begin to develop a sense of industry, according to Jacquelynne S. Eccles, writing for The Future of Children. There are several biological factors that can influence this stage of development.
The Contribution of Genetics
Plomin et. al., in a 1997 study published in Psychological Science, found a strong link between genetics and development. They conducted longitudinal research to compare adopted children with children living with their biological parents. Their findings show that adopted children bear a resemblance to their adoptive parents during early childhood but no similarities by middle childhood. During middle childhood and adolescence, the children became increasingly similar to their biological parents. This was reflected in both the cognitive and verbal development of adopted children.
Hormones and Their Effects
In "Child Development," Laura E. Burke writes that hormones account for some developmental differences in middle childhood. Hormones created by the endocrine and pituitary glands are responsible for most of the physical and growth changes that take place in middle childhood and beyond. Inherited conditions that cause growth hormone deficiency can severely impact the physical development of a child. Similarly, children born with a deficiency of the hormone thyroxine will have limited brain development, which can cause learning difficulties in middle childhood. Children are also affected by the release of sex hormones in the later stages of middle development as they move into adolescence.
Writing for the Journal of Nutrition, Sally Grantham-McGregor and Cornelius Ani, studied the effects of iron deficiency in children. Their research shows that children who experienced anemia in the first 2 years of their lives continued to have developmental difficulties during middle childhood. These included poorer cognition, behavioral difficulties and lower academic achievement. However, they do acknowledge that the socioeconomic backgrounds of the children included in the study may have influenced these findings.
The Impact of Disabilities
In their book, "Middle Childhood," Leanne Charlesworth, Jim Wood and Pamela Viggiani suggest that disabilities are a biological reason for a delay in development during middle childhood. They say that the U.S. Census Bureau of 2005 showed that 6.7 percent of U.S. citizens aged 5 to 20 years old have a form of disability. Specific disorders that they focus on are autism spectrum disorders, attention deficit hyperactivity disorder, and behavioral or emotional disorders. Although these disorders are often present from early childhood, it is often during middle childhood that they become clear and a diagnosis is made. Each of these disorders can impact a child's emotional, social and learning development during this stage.