After 270 trials, or about 20 minutes of training, liars were indistinguishable from truth-tellers on accuracy and response time.
"We think that, psychologically, the people basically learned that this is not me and the fake identity is me," Hu said.
The team is currently studying whether other measures of lying, such as polygraph machines or EEG brain wave measurements, can reveal practiced deception, or whether lies are completely undetectable using current methods, he said.
The findings have implications not just for would-be criminals, but also for lie-detection research, which usually attempts to spot deception immediately after a person is asked to lie.
"But in the real world, after a crime, there is usually a delay between the crime and the interrogation," giving the criminal a chance to practice their falsehood, he said.
Hu's team is currently studying whether people can improve their lies when asked to provide a false memory of events - for instance, when creating an alibi after a burglary.