People have varying opinions about what a personal robot should look like, and they change their minds based on what it is supposed to do, U.S. researchers say.

In a study at the Georgia Institute of Technology, participants were shown photos of either robotic, human or mixed human-robot faces and asked to choose the one that they would prefer for a robot's appearance.

While most college-age adults preferred a robotic appearance, nearly 60 percent of older adults said they would want a robot with a human face, and only 6 percent of older adults chose one with a mixed human-robot appearance, the study found.

"We found that participants, both younger and older, will assign emotional traits to a robot based on its face, which will determine what they are most comfortable interacting with," Akanksha Prakash, a School of Psychology graduate student who led the study, said.

Preferences among both age groups wavered a bit when participants were told the robot was assisting with personal care, chores, social interaction or for helping to make decisions, she said.

For chores, the majority of older and younger participants chose a robot with a robotic face, but for decision-making tasks, such as getting advice for where to invest money, younger participants tended to select a mixed human-robot appearance, while older adults generally preferred a human face.

"Those who selected a mixed face perceived the robot as more intelligent, smarter or wiser than one with a 'cute' robotic face. Perceived intelligence in appearance was an important assessment criterion for receiving assistance with decision-making tasks," Prakash said. "As a result, preferences for robotic appearance varied across tasks."