Scent was used as the conditioning stimulus

Field conditioning of sexual arousal in humans

Conclusion: The present study provides another demonstration of conditioned sexual arousal in men, specifically an instance of such learning that happened in a real-world setting. It also suggests that inhibitory learning may occur, at least with the affective measure.

The full text of the article is free, and the first author is the professor whose student found that an androstenol/androsterone mix altered observed flirtatious behavior and self-reported level of attraction to a man wearing the mixture.