According to the Extreme Intellect website, the average intelligence quotient (IQ) is between 85 and 115, which comes from dividing a person’s tested mental age by her chronological age and multiplying that number by 100. Half the population of the United States have IQs of between 90 and 110, with 25 percent higher than that and 25 percent lower. While there are indicators that a child may be in the high or low range of IQ, experts like David Palmer, Ph.D., warn that there are no “sure signs.” A designation of "mentally retarded" or "gifted" should be weighed against other factors such as emotional, communication and social skill sets, with learning disabilities often coexisting alongside a high IQ in a mix.
Signs that a child may have a lower than average IQ begin with walking and talking later than his contemporaries. Other signs include poor social skills in play-learn situations with other children, delayed self-care, hygiene, dressing and feeding skills. As the child grows older, difficulties in learning academic skills and poor job skills may also be indicators.
Signs that a child may have a higher than normal IQ may begin with early walking and talking, communication and social skills. She may also show a high energy level, interest in artistic activities, have rapid and complicated language patterns, as well as showing empathy with others and leadership among peers.
Some children may have both a high IQ and learning difficulties. According to "Parents' Guide to IQ Testing and Gifted Education" by David Palmer, children with attention deficit disorder are often in the normal to high range of IQ. They may be very good at computer games, hear several conversations at once and be very active in play, but at the same time seem unfocused, jump from one activity to another and score lower than expected on academic tests.