Scientists in California and Canada have developed a computer -- that knows when you're faking it.

A joint study by researchers at the University of California, San Diego and the University of Toronto has determined a computer system can accurately identify real or faked expressions of pain more accurately than people can.

Titled "Automatic Decoding of Deceptive Pain Expressions," the findings of the research are published in the most recent issue of Current Biology.

"The computer system managed to detect distinctive dynamic features of facial expressions that people missed," said Marian Bartlett, the study's lead author and a research professor at UC San Diego's Institute for Neural Computation, in a news release. "Human observers just aren't very good at telling real from faked expressions of pain."

Kang Lee, one of the study's senior authors and a professor at the Dr. Eric Jackman Institute of Child Study at the University of Toronto, said: "Humans can simulate facial expressions and fake emotions well enough to deceive most observers. The computer's pattern-recognition abilities prove better at telling whether pain is real or faked."

The research revealed humans could discriminate between real and faked expressions of pain pretty much as well as by random chance. Furthermore, even after training, that accuracy rate only improved to 55 percent. The computer system attains an85 percent accuracy.

"In highly social species such as humans," said Lee, "faces have evolved to convey rich information, including expressions of emotion and pain. And, because of the way our brains are built, people can simulate emotions they're not actually experiencing -- so successfully that they fool other people. The computer is much better at spotting the subtle differences between involuntary and voluntary facial movements."

The single most predictive feature of falsified expressions, the study said, is the mouth, how and when it opens. Fakers' mouths open with less variation and too regularly.

"Further investigations," said the researchers, "will explore whether over-regularity is a general feature of fake expressions."

In addition to detecting expressions of pain, the computer system in question looks to eventually be used to detect other deceptive behaviors in the real-world realms of homeland security, psychopathology, job screening, medicine, and law, the researchers said.

"As with causes of pain, these scenarios also generate strong emotions, along with attempts to minimize, mask, and fake such emotions, which may involve 'dual control' of the face," Bartlett said. "In addition, our computer-vision system can be applied to detect states in which the human face may provide important clues as to health, physiology, emotion, or thought, such as drivers' expressions of sleepiness, students' expressions of attention and comprehension of lectures, or responses to treatment of affective disorders."