How do educational psychologists define "attention span"?

How do educational psychologists define "attention span"?

Louis Pugliese (Lecturer in Educational Psychology, CSUN, Certified by the National Board for Professional Teaching Standards) gives expert video advice on: What conditions stimulate learning?; How can I help my child be more motivated in the classroom? and more...

Attention span, simply, is the ability to fixate or to focus on the features of a new stimulus; meaning: to continue to explore any novel parts of that stimulus, anything new. That stimulus can be something a teacher is talking about, presenting new information. It certainly can be information that is presented visually, in a media sense, or in the form of a picture. It could be also focusing on the steps in a task, that have been, hopefully, given direction clearly to a learner or a student. Who can then follow the directions for completing a cognitive task.