To intentionally forget is to remember differently, on purpose. Importantly, for scientists and therapists, intentional forgetting also may be an ability that can be practiced and deliberately strengthened.

In the new study, a team led by Tracy Wang, a postdoctoral psychology fellow at the University of Texas at Austin, had 24 participants sit in a brain-imaging machine while they conducted a memory test. Dr. Wang’s co-authors were Jarrod Lewis-Peacock of the University of Texas and Katerina Placek of the University of Pennsylvania.

In the experiment, each subject studied a series of some 200 images, a mix of faces and scenes, and identified the faces as male or female, and the scenes as indoor or outdoor. Each image appeared for a few seconds, then disappeared, at which point the participant was asked to either remember or forget it; after a few seconds delay, the next image appeared. The brain scanner focused on activity in the ventral temporal cortex and the sensory cortex, regions that are especially active when a person focuses mental attention on simple images such as these.

After the participants finished, they were given a short rest and then a test. They looked at a series of images — ones they’d seen earlier and ones they hadn’t — and rated how confident they were at having seen each one. They scored well: they recalled 50 to 60 percent of the images they’d been instructed to remember, and successfully had forgotten about 40 percent of the images they tried to erase from memory.

The payoff came with the imaging results. When a subject’s brain activity — a measure of internal mental attention — was especially high or especially low, it typically corresponded to a failed attempt to forget an image.

A concentrated effort to forget an unwanted memory did not help dim it, nor did mentally looking the other way. Rather, there seemed to be a sweet spot — neither too little mental attention, nor too much — that allowed a memory to come to mind and then fade, at least partially, of its own accord. You have to remember, just a little, to forget.

“This suggests a new route to successful forgetting,” the authors concluded. “To forget a memory, its mental representation should be enhanced to trigger memory weakening.”