Ambiguous (adjective): open to more than one interpretation

The room was a white, six-sided cube. One fluorescent light shone from the center of the ceiling, illuminating a perfect glass cylinder perched on a white table. Closer inspection of the glass cup revealed carved markings, measuring precisely 500 mL. Water filled the cup to exactly 250 mL.

A simple sign read: describe what you see.

Participants of the experiment had been streaming in and out, examining the glass of water and calling it “half full” or “half empty.” In the camera room, the researchers nonchalantly scribbled their notes on clipboards with black ballpoint pens—the classic results, optimism and pessimism, filled several pages already.

A few interesting people did amuse them.

“It's not a bad reed soaker,” said a young woman wearing a sweatshirt of her favorite band. She nodded cheerfully at the camera in the corner and left.

The second woman scrutinized the cup of water for ten silent seconds before saying, “Unidentified liquid in a cylindrical glass.” Her heels clicked as she spun away.

The third person to walk in was a man sporting a white collared shirt and a blue tie. He took one look at the cup and winked. “Keep it this way and sell it. The debates over it would be good marketing value.”

At this, the researchers burst into laughter. A few of them joked about abandoning their thesis and just going for it, until a child walked in.

Striding straight for the glass of water, the little boy picked it up and drank it in one large breath—clipboards clacked to the ground with each bob of his throat.

“Ah, delicious,” he smiled widely at the camera. “Thanks!”