Here is a description of a attention disorder that does not involve hyperactivity. Inattentive or non hyperactive ADD is a type of processing disorder. With this type of mental distraction, children and adults can be looking right at you, and not be distracted at all. However, they may still miss important information.
The reason for this is that these people process input information slower than a normal pace. As a result of this partial processing of incoming information, they often struggle with memory and require a relearning of certain things. These people are what can be called single-threaded, in that, they prefer to manage one thing at a time. The problem they have is understanding things from a general perscptive, not at the detail level. They are ofter quite and do not bother others, and, as a result, they are often passed under the radar allowing others to minimize of miss ADD. Other people may take over their work to help out or get things done quickly which therefore encourages them to become more dependent.
This type of ADD is one that many times gets overlooked, but should not be taken lightly as these people generally expect too little of themselves, avoid risks, and stay in a quite, safe place.