Cognitive psychologists, neurologists and other researchers are beginning to study the impact of constant multitasking, finding that just talking on a cell phone takes its own considerable toll on cognition and awareness, known as “inattention blindness.”

One possible explanation: a cellphone conversation taxes not just auditory resources in the brain but also visual functions, prompting the listener to, for example, create visual imagery related to the conversation in a way that overrides or obscures the processing of real images.