love-4
Explanation
The Joke
The comic begins with a character explaining a neurological observation: "Humans don't just have physiological responses to certain stimuli. We also have emotional responses to our physiological responses." Extending this logic, she notes: "If you meet someone and find your heart rate going up, you will assume you're attracted to that person, even if you aren't."
Her companion then draws the sinister conclusion: "So we can decide who falls in love with whom? If you inject two people with adrenaline, you can ensure that they find each other attractive?" The woman confirms this with a grin, holding up a syringe and announcing: "I call it Cupid's Arrow."
The joke is that the romantic concept of "Cupid's Arrow" -- the mythological force that makes people fall in love -- has been reduced to a literal syringe of adrenaline. The comic takes a real psychological phenomenon (misattribution of arousal) and pushes it to its darkly logical extreme: if people mistake physiological arousal for romantic attraction, then you can manufacture love with a needle.
The Humor
The humor comes from the unsettling gap between the romantic ideal of love and the reductionist, pharmacological hack being proposed. Calling a syringe "Cupid's Arrow" is both a clever pun (arrows pierce the skin, as do needles) and a deeply unromantic reimagining of one of mythology's most beloved figures. The woman's cheerful enthusiasm for what is essentially a consent-violating love drug adds a layer of dark comedy that is very characteristic of SMBC.
References
The comic references the psychological concept of "misattribution of arousal," demonstrated in the famous 1974 Dutton and Aron bridge experiment, in which men who crossed a fear-inducing suspension bridge were more likely to find a female interviewer attractive than those who crossed a stable bridge. The effect occurs because people misinterpret physiological arousal (elevated heart rate, adrenaline) from one source as romantic or sexual attraction.