Ideally, by the age of 8 years a child should have developed a preferred side of functioning (unilaterality). This means that if a child is right handed the right eye should act as the leading eye at both far and near distance, the right ear, foot etc. and vice-versa if left handed (with the possible exception of right ear preference for the majority of the population). While both ambiguity of laterality and cross laterality are common in the general population and do not by themselves cause specific learning difficulties, cross laterality is often an additional factor in children diagnosed with specific learning difficulties. Some research has linked cross laterality to the continued presence of an Asymmetrical Tonic Neck Reflex (ATNR).