6

【解析】 动词辨析。选项所在句子When people place their trust in an…, their brains release oxytocin, a hormone that  6  pleasurable feelings and triggers the herding instinct…，意为“当人们产生信任感，大脑就会产生一种……的荷尔蒙”，that  6  pleasurable feelings and triggers the herding instinct…是定语从句，修饰hormone。and连接并列的两个动宾短语，可知选项的动词应与trigger意思相近，为“产生”的意思。因此C选项produces正确。