Is it rude to tweet or type during a live presentation?

A new phenomenon has exploded at industry conferences: Audience members burying their heads in laptops and cell phones instead of making eye contact with the speakers. While many speakers have learned to embrace this crowd reaction, John Medina, the director of the Brain Center for Applied Learning Research at Seattle Pacific University, says doing two things at once can slow a person’s brain. “Multitasking, when it comes to paying attention, is a myth,” he writes. “The brain natu…