With blastoff just a week away, scientists were trying to answer a tricky question Monday - which two cosmonaut monkeys get to go?

Seven macaques are now in training at the Plesetsk cosmodrome in northwestern Russia. Two of them will spend 14 days in space aboard the Bion spacecraft, which is scheduled for launch Dec. 24. Scientists will also choose a two-monkey backup crew.

“It’s essential to get a friendly soul in a seat next to you,” the daily Moskovsky Komsomolets said in a report from Russia’s Biomedical Institute.

If the monkeys are hostile to each other, their heartbeats would be faster than normal and distort the experimental data, an institute scientist, Inessa Kozlovskaya, said.

The monkeys will also play computer games during the flight to amuse themselves, she said.