I teach a yearly Professional Development class, in which I often implore students to put their phones to work for them.  I warn students that smart phones can be a terrible master if they allow it.  I am not alone with this claim.  Recent research from the University of Texas found:

​“It didn’t matter whether a person’s smartphone was turned on or off, or whether it was lying face up or face down on a desk. Having a smartphone within sight or within easy reach reduces a person’s ability to focus and perform tasks because part of their brain is actively working to not pick up or use the phone.