People spend 'half their waking hours daydreaming'

I read news about people and daydreaming.
        
            According the news, people spend half of their time daydreaming. In experiment, 2,200 volunteer downloaded app that surveyed them about their thought and mood at random time of day and night. The study suggested minds wander is caused by demanding tasks at least 30% of the time. The expert said "This study shows that our mental lives are pervaded, to a remarkable degree, by the non-present" 

I don't understand this news exactly but I try to understand English news.