U.S. psychologists say humans might be losers if technological nature -- such as robotic dogs or Web cams viewing nature scenes -- replaces the real thing.

University of Washington psychologist Peter Kahn said technology increasingly is encroaching upon human connections with the natural world and that intrusion might produce one of the central psychological problems of our times.

"We are a technological species, but we also need a deep connection with nature in our lives," said Kahn, lead author of the study.

Kahn and graduate students Rachel Severson and Jolina Ruckert studied the psychological effects of interacting with various forms of technological nature.

One experiment showed people recovered better from low-level stress by looking at an actual view of nature rather than seeing the same view displayed on a high-definition television set.

"What do we compare technology to? If we compare it to no nature, technological nature works pretty well. But if we compare it to actual nature, it doesn't seem to provide as many psychological benefits," Kahn said.

Another experiment showed children in some ways treat robots as other beings. But Kahn said compared with interacting with a real dog, their interactions with the robots were not as social or deep.

The study is reported in the journal Current Directions in Psychological Science.