'Inattention blindness' due to brain load

“Engaging attention on a high load task has a strong effect on the brain’s response to the rest of the world,” says Professor Nilli Lavie of the UCL Institute of Cognitive Neuroscience.

"It reduces both the level and precision, or ‘tuning’, of neural response to anything else around us that is not part of the task. "These effects of load on neural response explain inattentional blindness. Although our environment hasn’t changed, the change in our brain response under load leads to inability to perceive otherwise perfectly visible stimuli outside our focus of attention,” she explains.