By Emily Sohn

It's not a particularly attractive picture. That much, Lorie Novak and her mother, Geri, agree on. Still, Geri Novak has fond memories of that day in Los Angeles 10 years ago, when all 25-plus members of the extended family got together. Lorie, on the other hand, looks at the photo and remembers what her 71-year-old mother has forgotten: "the big fight we had that day."

For all the crisp realism they seem to offer, photographs have a funny way of playing tricks with memory. From the kinds of pictures we take to the ones we choose to display, photos are much like family history: What really happened is often a matter of interpretation. "How often do you say, 'I wish I had a camera to freeze this image'?" asks Dartmouth College professor Marianne Hirsch. The assumption, she says, is that unphotographed events suffer a certain vulnerability. "People say if there was a fire, the first thing they would save is their photo albums. We almost fear we'll lose our memories if we lose our albums."

That may literally be true. Harvard psychologist Daniel Schacter found that people in his experiments who watched a video remembered best the scenes that had been reinforced by photographs. "It's as if some photographs strengthen some aspects of memory at the expense of others," Schacter says. But photos can create false memories, too. Study participants shown related photographs that were not included in the video often confused these images with real scenes from the video, even though they knew some of the photos were false. His findings may confirm the popular idea that some memories, especially the earliest ones, may be based on photographs, not real events, Schacter says.

That kind of memory distortion isn't always accidental. "There's a lot of selection in what photographs survive in a family album," Hirsch says. Old boyfriends get snipped out. Awkward teen years end up in boxes. Even photographs that make it into albums don't always tell the whole truth. "You're looking at a happy family photo of an event," says Lorie Novak, a New York City-based artist who uses snapshots in her work. But "you remember how traumatic that day was." So though photos may shape memory, without stories, pictures lose their context. Novak's favorite family photograph, for example, shows her as a 2-year-old, sitting next to a portrait of her at the same age. In that painting, she wears a pink frilly dress. But Novak, 47, remembers wearing a T-shirt and Mickey Mouse ears the day it was painted. In lectures, she often talks about the photo to illustrate the discrepancy between memory and pictures. "Stories become attached to photographs that then become a memory of that time that may not be the true story," Novak says. But in this case, she was relieved to learn from her parents, memory proved truer than the image, which had been altered by the painter. She hadn't worn the pink dress after all.

Finally, of course, our most cherished photographs most notably tell stories of loss: Once a loved relative is gone or a special day ends, only the photo remains. And the memory.