This story is one of four written by high school students who participated in The Washington Post’s 2011 Digital Workshop for Young Journalists, each with a corresponding video.

Lying in the straw of her pen in the National Zoo’s Think Tank, Iris, a 34-year-old female orangutan, tossed a ball as she fiddled with her blanket. She glanced out the window to the last stop of “O-Line,” a series of cables and towers that lead the orangutans over pedestrian walkways from the great ape house, and saw another ape sliding down. She dropped everything and lumbered over as the new arrival came closer.

They met on opposite sides of the glass and paused. Iris grabbed the window frame. The visitor did the same. Iris raised her leg out to the side, reaching up over her head. Again, the other ape copied. In this monkey see, monkey do exhibition, it was hard to tell if the glass was a window or a mirror.

Sights like these are commonplace in this interesting and thought provoking exhibit.

Tucked between the great ape house and the lion and tiger pits, “Think Tank is a place to think about thinking,” according to the National Zoo’s Web site. Researchers there study different questions about thought in other animals. How do they communicate? What is their capacity for memory, or their ability to learn and adapt, or to feel empathy? And, most importantly, what can they teach us about ourselves?

The answers to these questions may lie in the minds of the zoo’s six orangutans.

“These are guys that are able to think like we are,” said Think Tank volunteer Betty Reinecke. “They can solve problems. If they’re presented with an obstacle, they can plan their way around it.”

Glancing at Kiko and Iris, the two apes in the Tank on this day, it’s hard to tell they are anything like us. Their matted red fur hangs in knots, tangled with the straw that covers their enclosure’s floor. But their eyes gaze knowingly out of the pen as they scan the crowds of children fogging the glass with their breath. Just who is studying whom here?

“Well, they’re not that different after all,” Reinecke said. “Our DNA is something like 90 percent the same.”

Our DNA may be similar, but what exactly does that mean when it comes to thinking? This is the underlying question for researchers here. Are these apes capable of some of the things that we believe make human beings unique as a species?

“I think that we as humans like to hold ourselves at a very high level,” said great ape keeper Erin Stromberg, a researcher and caretaker at the exhibit. “It was thought that only humans could make tools, and that’s what set us apart from the rest of the animal kingdom. Well, not only can all the great apes make tools, monkeys can make tools, birds can make tools, dolphins can make tools. So here we have this characteristic that we thought only we could do, that was unique to us, and really, it’s not.”

At any time, several research projects are being done at the Tank, studying everything about the primates’ minds, including high-level topics like metacognition (knowing your own mental limitations).

For Iris and Kiko, the research may just be a way to stay occupied during the day.

“I think (the Think Tank) is only partly for us to learn,” Reinecke said, “and partly to keep the animals interested.”

Researchers must be doing something to keep them engaged, because the orangutans participate in the research completely voluntarily. Scientists don’t force them to come to the Tank; instead, the apes can come over whenever they want on the O-Line. Volunteers say the aerial pathway between enclosures, which sends the apes swinging over the crowds of pedestrians below, is the only one of its kind in the country.

Once they clamber down from the green steel tower into the Tank’s enclosure, they find the hanging hoops and climbing ropes that create a jungle gym for an ape’s body and mind. White walls and wooden benches frame the pen, along with the unending questions and exclamations of children and adults watching from the other side of the glass. It’s never silent in the Think Tank.

“We’ve been to San Diego Zoo last year, and London Zoo in the U.K., but … haven’t seen anything quite like this,” said Mary Wort, a tourist from London.

“People always ask me if [the apes] surprise me with their intelligence, but they never really surprise me -- they amaze me,” said Stromberg.

But for Stromberg the research doesn’t come without challenges. For example, Stromberg is working on a project dealing with the orangutans’ ability to plan ahead, giving them a tool in the ape house that can open a box in the Think Tank. Do the apes have the foresight to bring the tool with them across the O-Line? The orangutans’ intelligence is a major obstacle for the scientists in this case.

“They’re incredible tool users,” said Stromberg, “So if we give them something that’s say, hard metal, they could trigger the electrical system, dismantle the O-Line, things like that.

“Also, they’re looking for you to mess up — they’re very opportunistic. They’re double-checking our locks once they get into the cage, making sure nothing was left undone,” she said. “But it’s a lot of fun as well. You get to know them as if they’re your own children.”

Iris, worn down as the day ended, curled up with her blanket at the base of the viewing glass. Excited toddlers squealed and pointed as Iris sat, bleary-eyed. Finally, tired of the staring eyes, she yanked the cover over her head and dozed off in the straw.

“They’re each unique, they have very different personalities,” said Reinecke, “You can learn almost any lesson about ourselves you want from these guys, I think, but the most important thing isn’t the ways we’re different; it’s the huge similarities between us.”