This week's Lab Rat challenge involves the housemates taking part in experiments such as the 'Eyes on the Prize' experiment.
[Photo Gallery - Big Brother Lab Rats task]
During the 'Eyes on the Prize' task, the housemates must wear eye-tracking glasses and remain focussed on a plinth in the middle of the room.
Big Brother has provided constant distractions for the contestants, including a 7-foot python, which was carried around the room during Shievonne's task.
Other distractions included a Justin Bieber lookalike, a burlesque dancer and a group of superfans, fawning over the housemates.
Benedict Garrett and Lauren Carre are the two housemates facing possible eviction on Friday.
Big Brother continues every night on Channel 5.