When the sum total of human knowledge rests an arm’s length away in each person’s pocket, why do we have to remember anything anymore?

On an average day most of us check our smartphones 47 times, and nearly double that if we’re between the ages of 18 and 24, which might explain why some of us have such a hard time processing the information we take in to form memories. Smartphones alter the way we walk, talk and think, and we’re barely keeping up.

“Everything is available through a Google search almost instantaneously, so what motive do you have to store useless info?” said Joseph LeDoux, who directs New York University’s Emotional Brain Institute.

Mr. LeDoux, whose work focuses on how the brain forms memories, said this instant-fact setup clouds our judgment on what information to filter and store. Since we’re no longer weighed down by having to retain trivial data, we are left with greater cognitive space. But how do we select what we remember?