"We could have projected, 'The happiness level today is 5,'" says graduate student Kirsten Boehner. "But we wanted to do something that would draw people into playing with it a bit more. People would stand there looking at it and say, 'Oh, the color is moving to red; that means there's a lot of stress.' That might not be the correct interpretation, but it provided a stimulus for people to reflect on emotions and talk about them.

"Ambiguity is not something you always want in your system," Boehner observes. "It's not something you want air traffic controllers to have. But for systems that are about inspiring creativity or reflection or conversation, it is really useful to signal to people that there's no right interpretation. It's about building new interpretations."

While such work may seem purely academic, "simplicity and ambiguity are incredibly important concepts," says Genevieve Bell, director of user experience for Intel's Digital Home Group. "I find them a useful vantage point for critiquing existing systems. There's been a startling disconnect between the people who develop computational technologies and the people that consume them."