Impairment, neglect, lack of nutrition and environmental poisoning are some of the factors that can affect intellectual development in childhood. The first five years of life are thought to be the most important in terms of not only social and emotional development, but also intellectual growth. If intellectual stimulation, such as children being spoken and read to, doesn't occur regularly or it can't be processed due to an impairment or the effects of a toxin, thinking and learning can be greatly affected.
Environmental poisons and the intellectual growth of children can be closely related. For instance, many studies have been done on lead poisoning in children, and the findings often suggest a negative affect on intellectual development. Even low levels of exposure to lead may have one of the worst impacts on intellectual development in childhood. Lead was once used widely in house paint, but due to study findings it's been banned in many parts of the world. Children can be exposed to lead by consuming flaking paint that contains lead, such as that on an old window sill, and it could affect their intellectual development.
Fluoride is another environmental factor that is thought to affect childhood intellectual development. Exposure to too much of it, even as a fetus, may harm brain tissue as well as the central nervous system. Lack of proper nutrition can affect intellectual development in childhood as well, since the body, including the brain, can't grow properly without needed nourishment. Studies show that school-age children who are hungry may have difficulty thinking and learning. This is why some schools provide breakfast and/or lunch programs for children who, due to poverty or neglect, don't have enough food at home.
Neglect can be one of the strongest influences on intellectual development in childhood. Babies and children need to be spoken to and interacted with, such as through reading stories and teaching about shapes, colors, letters and numbers. Even more than actual teaching, they need communication with adults to develop language and thinking skills. Emotional problems may also interfere with a child's ability to learn and develop at a normal rate. Hearing or vision impairments, especially those that aren't detected and treated early, may also hinder a child's intellectual development.