As we noted earlier, the topic of emotion has often been equally ignored by devotees of both Homo economicus and Homo psycbologicus, by rational choice theorists and advocates of cognitive psychological applications alike. The tendency to set affect aside has in part been a result of the difficulty of measuring emotional responses themselves, though. Supposing, for instance, you have just given your spouse or significant other a sweater for his or her birthday. He or she takes it out of its wrapping, holds it up and exclaims "just what I always wanted!" How do you know whether he or she really likes it, however? Your loved one may actually be delighted by the gift, of course. Alternatively, he or she may be rather disappointed, thinking "this isn't really my style" or "I wanted a new car." He or she may actively bate the sweater, but just claimed to like it because when we love someone, we usually try at all costs not to hurt their feelings.
Despite the simplicity of this example, there are a large number of different emotions potentially floating about here: mutual love, dislike of the sweater, liking the sweater, disapproval of one's partner's taste in clothes, the desire not to hurt the other's feelings, greed, disappointment, empathy, and so on. Despite the fact that the two individuals communicating the emotions are intimate friends accustomed to reading one another's emotional responses, neither can be absolutely sure which of several emotions the other is experiencing. If reading emotions in individual cases is this difficult, how can psychologists possibly measure people's emotions in an accurate way?