Children and adults classified with learning disabilities (LD) are individuals of normal intelligence, but they suffer with mental information processing difficulties. Several definitions refer to persons with LD as reflecting a heterogeneous group of individuals with intrinsic disorders that are manifested by specific difficulties in the acquisition and use of listening, speaking, reading, writing, reasoning, or mathematical abilities. Most definitions assume that the learning difficulties of such individuals are:

• Not related to inadequate opportunities to learn, general intelligence, or significant physical or emotional disorders. The basic disorders are linked to specific psychological processes (such as remembering the association between sounds and letters).
• Not related to poor instruction, but to specific psychological processing problems. These problems have a neurological, constitutional, and/or biological base.
• Not manifested in all aspects of ...