The baseline test was an examination designed to measure any emotional deviance experienced by Nexus-9 replicants in the course of their work. To be "off baseline" would be considered a failure of such test.
The baseline test constituted a part of police protocol in the Blade Runner section of the force. In contrast with its predecessor, the Voight-Kampff Test, the baseline test was conducted by an unseen interviewer who carried out the examination through a monitoring device that analyzed the subject's physiological responses. The device was embedded in the wall of a small cell-like room that also contained a single chair. While the test was administered, the subject would sit in the chair and face the monitoring device. The length and content of the test was based on the subject's response time. A replicant close to baseline would experience a shorter test than a replicant who exhibited significant deviance because the interviewer would take a more aggressive and provocative approach to verify that deviance.
Officer KD6-3.7 or "K" was seen to be subjected to the baseline test on two occasions: June 30 and July 4, 2049. The first test was administered after K retired Sapper Morton in a particularly violent confrontation. K passed the test with flying colors and received bonus pay. The interviewer called him "Constant K", implying K had a reputation for seldom deviating from the baseline.
K was forced to take the test again later, when he was caught outside of Stelline Laboratories after having strayed from his initial mission to find and kill Rick Deckard and Rachael's child. Having been emotionally compromised by the assumed revelation that his false memories actually happened, K failed the test and was brought before Joshi to be debriefed. Joshi informed him that his results were bad enough to have him retired on the spot. K defused the situation by claiming that he had completed his mission and the child was dead. Placated, Joshi then gave K forty-eight hours to return to his baseline and retake the test, although she was privately aware he would use the opportunity to escape.
Behind the scenes
"In the original Blade Runner, the Voight-Kampff method was used to distinguish Replicants from humans. In this film, a more advanced technology analyzes a Replicant's operational stability. 'The Baseline is designed to test the effects of a Blade Runner's job on his brain and psyche', explains Ryan Gosling. 'Because they have to kill their own kind, they constantly need to be assessed as to whether their work is having some kind of moral impact on them'"
The version of the test shown in the final cut of Blade Runner 2049 was actually a rewrite done by Gosling himself. In the original script, the test involved K simply reciting a poem while his emotional state was passively monitored. Gosling's changes were inspired by techniques that actors used to learn Shakespeare plays.
Early in Blade Runner 2049's production, the baseline test also took a different form. Replicants would have received the test before undertaking a mission, rather than after. The test was also less impersonal, and would have been administered by an interviewer who was present in the room with the replicant. A scanner would have moved over the replicant while he lay on an examination table during the test.
The poem that begins the test and is quoted word-by-word throughout is from Vladimir Nabokov's novel Pale Fire.
The unseen interviewer who leads the baseline test is voiced by actor Mark Arnold.
The interrogator remarks "Constant K", at the end of the first Baseline Test, possibly making a reference to the K-complex, which is a waveform that may be seen on an electroencephalogram (EEG), in regards to K's consistent behavior and baseline. K-complexes have two proposed functions: first, suppressing cortical arousal in response to stimuli that the sleeping brain evaluates not to signal danger, and second, aiding sleep-based memory consolidation.