Extraneous stimuli is an action or thought stemming from outside someone's focus and has no relevance to the person's current task. Those who suffer from Attention Deficit Hyperactivity Disorder (ADHD) are often plagued with distraction arising from extraneous stimuli and struggle to stay focused and often shift focus from one thing to another.
There are many symptoms to inattention on top of the distractions from extraneous stimuli, including the inability to sustain attention during tasks or play, forgetfulness, appearing to not be listening when spoken to and the inability to complete tasks, such as homework or chores, and not just because they are opposed to doing them. With hyperactivity, there are other symptoms including fidgeting, talking excessively, running around and climbing in situations where it is inappropriate and difficulty in playing quietly.
ADHD cannot be cured but it can be eased by adapting the environment or by schools making accommodations for children with problems. For example, a daily schedule that specifies what task should be performed at what time can help keep a person on track. A work space that limits distractions, such as cellphones, televisions, unproductive Internet browsing, too many people or loud music, can also be helpful.