Human Characteristics

In Blade Runner the differences between human and replicant have grown so thin that a fictional mechanical device, the Voight-Kampff test, is required to distinguish them.   In the film, Eldon Tyrell informs us that the device measures such things as "capillary dilation of the so-called blush response, fluctuation of the pupil and involuntary dilation of the iris", in reaction to a series of psychological questions calculated to elicit emotional responses. The differences in the reactions between humans and Replicants provide the means by which they can be identified. The Nexus-6 Replicants, however, have been designed with a four year life span because it is feared that after this time they will begin to develop their own emotional responses, thus making them indistinguishable from human beings by any means .
Compare the reactions to the Voight-Kampff test by Leon (an average Replicant) and Rachael (arguably as near human as any Replicant has ever been). Leon, programmed to kill on command, has the emotional capacity of a child. Consider what gets him so upset: The proposed scenario of a tortoise (a turtle), being forced to suffer at his hand generates such a powerful emotional response that he reacts the only way his creators have programmed him to: violence. Much like a young child who throws a tantrum rather than face the reality of an unpleasant situation, Leon murders his tormentor, rather than confront the imagery that the scenario has evoked.
Rachael, on the other hand, has had human memories artificially implanted. What this implies is that she has become "cushioned" against the impact of these emotionally charged scenarios.
Deckard: "A wasp crawls on your leg..."
Rachael: "I'd kill it."
Rachael does not even require a moment's hesitation to respond. She is inured to the incidental cruelties inherent to the human condition. To her those cruelties have become commonplace, even routine. She can calmly answer questions that would send other Replicants... [continues]

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