Poul Anderson 
Sentiment, Inc. [EPUB ebook] 

The way we feel about another person, or about objects, is often bound up in associations that have no direct connection with the person or object at all. Often, what we call a “change of heart” comes about sheerly from a change in the many associations which make up our present viewpoint. Now, suppose that these associations could be altered artificially, at the option of the person who was in charge of the process….