So some years later, he naturally found himself on that bike path with three blind companions. Two of the bikers, Daniel Kish and Brian Bushway, were experts at echolocation. The third, Megan O'Rourke, was a beginner, at least as far as biking was concerned, and she was a bit nervous.
"They did a few things to make sure they didn't run into each other," Rosenblum said. They twisted plastic ties onto their spokes to make a clicking sound so they could always know where the other bikers were. They also made a clicking sound with their tongues, about once every two seconds, he added, which they could hear reflected back from the curbs, shrubs, parked cars, and other obstacles.
Riding down the street was the scariest part, but "once they were on the bike trail they just went nuts," Rosenblum said. "They had a great time. They never went off the trail. They can hear texture. They can hear the difference between the dirt trail and the grass along the side of the trail."
Of course, he's not suggesting that biking blindfolded down a narrow path is easy. Both Kish, who was diagnosed with retinoblastoma in both eyes at four months and has never been able to see, and Bushway have honed their skills to near perfection over the years. It takes practice to get that good.
But here's something anyone can try. Make a sound -- even hissing will work -- as you approach a moveable wall blindfolded. The sound changes slightly, depending on the distance to the wall, and after about 10 minutes you should be able to do it consistently without running into the wall. At least that's how it works in Rosenblum's lab.
Echolocation is just one of several ways that we can use our various senses much more effectively. Your nose, for example, is a bit of a marvel.
Rosenblum soaked a long rope in oil, giving it a faint smell, and laid it out in a twisted pattern on the lawn at the Riverside campus. His students were blindfolded and equipped with headphones and heavy gloves. Using only their noses, they were told to find the rope and follow it.
"The difference in odor intensity between the two nostrils allows us to track a scent like a dog," he said. If the odor is strong in the right nostril than the left, turn right.
The students, he said, had no trouble finding the rope and following its meandering course.
Some changes in sensor perception take a little longer to accomplish, but not as long as might be expected. In just 90 minutes, he said, a blindfolded person should see improvements in hearing, and possibly even smell.
The brain makes that adjustment in the same way that blind persons enhance their hearing, by redirecting traffic from the visual cortex to the auditory system, but in the case of a blindfolded person, the change is temporary. After about 24 hours, the system returns to its default settings.