The search for extraterrestrial life might have more luck listening for sentient machines than for sentient beings, a prominent researcher in the field says.

SETI, the Search for Extraterrestrial Intelligence, has until now sought radio signals from worlds like Earth, but lead SETI astronomer Seth Shostak argues the time between aliens developing radio technology and moving on to artificial intelligence would be short, the BBC reported Monday.

The odds favor detecting such alien AI rather than "biological" life, Shostak said in an article in the journal Acta Astronautica.

While evolution can take a long time to develop beings capable of communicating beyond their own planet, he said, technology would already be advancing fast enough to eclipse the species that created it.

"If you look at the timescales for the development of technology, at some point you invent radio and then you go on the air and then we have a chance of finding you," he said.

"But within a few hundred years of inventing radio -- at least if we're any example -- you invent thinking machines; we're probably going to do that in this century.

"So you've invented your successors and only for a few hundred years are you ... a 'biological' intelligence," Shostak said.

John Elliott, a SETI researcher at Leeds Metropolitan University, says Shostak's feeling is not uncommon in the community.

"You have to start somewhere, and there's nothing wrong with that," Elliot said.

"But having now looked for signals for 50 years, SETI is going through a process of realizing the way our technology is advancing is probably a good indicator of how other civilizations -- if they're out there -- would've progressed.

"Certainly what we're looking at out there is an evolutionary moving target."