In general, images with people in them are the most memorable, followed by images of human-scale space — such as the produce aisle of a grocery store — and close-ups of objects. Least memorable are natural landscapes, although those can be memorable if they feature an unexpected element, such as shrubbery trimmed into an unusual shape.

Alexei Efros, associate professor of computer science at Carnegie Mellon University, says the study offers a novel way to characterize images.

“There has been a lot of work in trying to understand what makes an image interesting, or appealing, or what makes people like a particular image. But all of those questions are really hard to answer,” says Efros, who was not involved in this research. “What [the MIT researchers] did was basically approach the problem from a very scientific point of view and say that one thing we can measure is memorability.”

Predicting memorability

The researchers then used machine-learning techniques (a type of statistical analysis that allows computers to identify patterns in data) to create a computational model that analyzed the images and their memorability as rated by humans. For each image, the computational model analyzed various statistics — such as color, or the distribution of edges — and correlated them with the image’s memorability.

That allowed the researchers to generate an algorithm that can predict memorability of images the computational model hasn’t “seen” before. Such an algorithm could be used by book publishers to evaluate cover art, or news editors looking for the most memorable photograph to feature on their website.

Oliva believes the algorithm might also be of interest to camera manufacturers, and Isola is thinking about designing an iPhone app that could immediately tell users how memorable the photo they just took will be. For that application, the main challenge is getting the algorithm to work fast enough, Isola says.

Other possible applications are clinical memory tests that more precisely reveal what aspects of visual memory are deficient in specific psychological or brain disorders, and games to help train the memory.

The researchers are now doing a follow-up study to test longer-term memorability of images. They are also working on adding more detailed descriptions of image content, such as “two people shaking hands,” or “people looking at each other,” to each image’s memorability map, in an effort to find out more about what makes the image memorable.

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Anne Trafton, MIT News Office
Massachusetts Institute of Technology