It could be the name of a math teacher in high school, the title of a television show or what you meant to get at the store. You know you know it — it’s right there — but you can’t bring the memory forward.

Memory makes things easier; forgetting can make things hard. “As we navigate our lives, we have these periods in which we're frustrated because we're not able to bring knowledge to mind, expressing what we know,”explained Anthony Wagner, one of the researchers behind a recent study that used new tools to explain why it is that we are sometimes unable to call up something stored in memory.

“...The things that happen even before you begin remembering are going to affect whether or not you can actually reactivate a memory that is relevant to your current goal.”

The Stanford and University of California, San Francisico team's work is also providing clues as to why some of us seem to have better recall than others, and the role distracted attention, such as from media multitasking, plays in memory problems.

Researchers tracked attention lapses and their relation to recall in 80 study subjects between the ages of 18 to 26. They monitored subjects’ brain activity using an electroencephalogram (EEG) that looked specifically at certain brain waves while they performed tasks like identifying gradual changes in previously studied items.

Increases in these brain waves, known as posterior alpha power, “have been related to attention lapses, mind wandering, distractibility and so forth,” explained lead author, Kevin Madore, a Stanford postdoctoral fellow, in a statement.

The size of subjects' pupils was measured as they performed memory tasks. “We... know that constrictions in pupil diameter — in particular before you do different tasks — are related to failures of performance like slower reaction times and more mind wandering,” Madore explained.

Subjects reported how well they felt they were able to engage with multiple media sources, like texting and watching television, within a given hour. By comparing memory performance between individuals, the researchers found that subjects who reported they were less able to maintain sustained attention and those who were heavier media multitaskers both performed worse on memory tasks.

The study only shows a connection between media distractions and attention and memory. As Madore explains, “We can't say that heavier media multitasking causes difficulties with sustained attention and memory failures, though we are increasingly learning more about the directions of the interactions.”

You need to be ready to remember; it’s a goal-directed kind of thought. There are things you can do to make recall more likely. Limit distractions in your surroundings, and consciously focus your attention and readiness to remember. Said Wagner, the Lucie Stern Professor in the Social Sciences in Stanford's School of Humanities and Sciences. “While it's logical that attention is important for learning and for remembering, an important point here is that the things that happen even before you begin remembering are going to affect whether or not you can actually reactivate a memory that is relevant to your current goal.”

The study is published in Nature.