The fear most Gens feel about Simes. (House of Zeor, Ch 3) '"You're frightened! Don't you realize that it is Gen fear that triggers the worst Sime instincts?"'

"Gen Fear" is an emotion that modulates the selyn fields around the Gen in a very specific way, making the Gen more conspicuous to Sime senses, and to the junct more inviting.  The same emotion experienced by a Sime would affect the local selyn fields in a perceptibly different way.