Your brain was designed to be distracted

 By DAPHNE LEPRINCE-RINGUET, WIRED.

https://www.wired.co.uk/article/brain-distraction-procrastination-science

While it may seem that you are continuously focusing on reading this … the reality is that you’re zooming in and out of attention up to four times per second.  During those periods of distraction, the brain pauses and scans the environment to see if there is something outside the primary focus of attention that might be more important. If there is not, it re-focus back to what you were doing.  The reason why we are not aware of those gaps is because the brain tricks us into perceiving reality as a continuous movie.

Why does our brain make us go through attention pulses at such a fast rate? Researchers suggest that it corresponds to an evolutionary advantage. “Think about when life was more dangerous," Fiebelkorn says. "You would have to constantly be on the lookout, you would want to always be aware if there was something around you with bigger teeth.”

“Whether you are talking about the hyper-focused type of ADHD or the distractible type, you can easily draw a parallel with the two states that normal brains alternate between,” she says. “It could be that brains affected by ADHD are unable to balance between the two attentional spaces and instead get locked into one or the other.”