in a busy intersection. Kinsey, his caretaker, was trying to usher him back home when a motorist called 911, believing the silver toy Rios was holding might be a gun.

North Miami police officers rushed to the scene, surrounding the two men. Kinsey thrust his hands in the air, begging police not to shoot, loudly yelling that Rios had a toy, not a gun. Among the key evidence: Bystander video of the confrontation showing Kinsey lying on the ground, his hands up in surrender.

The scene commander radioed that the man appeared to be “re-loading.”

Aledda fired his M4 rifle. Kinsey was shot in the thigh and survived, although fragments of the bullet remain embedded in his body. Rios was unharmed.

Prosecutors said Aledda was not justified in shooting at Rios fromcontrol groups.

"Rather than just comparing them to people who did nothing, we compared them to a group of people who had fun but weren't mentally challenged as much," Park says.

That "social group" did things like watch movies or reminisce about past vacations. Another control group worked quietly at home, listening to the radio or classical music or playing easy games and puzzles.

Park's research, which was published in the journal Psychological Science, showed that not all activities are created equal. Only people who learned a new skill had significant gains.

"We found quite an improvement in memory, and we found that when we tested our participants a year later, that was maintained," Park says.

The greatest improvement was for the people who learned digital photography and Photoshop — perhaps, Park says,