When you look back over your relationships with people (and even products), there is a common pattern. You meet them, and you feel an overall sense that you like them. When you think about why you like them, there are all sorts of wonderful characteristics that come to mind. Some time later, if something goes wrong with the relationship you look back and realize that there were all sorts of other attributes of that person that you seem to have missed or glossed over.
And then you blame yourself for not seeing the negatives from the beginning.
As it turns out, though, there are powerful psychological mechanisms that affect your beliefs in ways that create the feeling that there is a high degree of consistency in what you like and dislike. Many of these mechanisms were described by Leon Festinger in the 1950s in his theory of cognitive dissonance, and more recently have been incorporated into theories by Paul Thagard in a 1989 paper in Behavioral and Brain Sciences; and by Steve Read and Amy Marcus-Newhall in a 1993 paper in the Journal of Personality and Social Psychology.
The basic idea in these theories is one of spreading coherence. These theories propose that you have attitudes (I like this person.), knowledge about them (This person is funny; This person is self-centered), and beliefs (I like funny people, I don't like self-centered people).
When you like someone, that tends to reinforce all of the knowledge you have that is consistent with that attitude. So, when you think about why you like a person, you will focus on qualities like being funny rather than qualities like being self-centered. The negative traits get put into the background. Sometimes, they even get re-interpreted. The person you like isn't self-centered, but rather is driven and hard-working.
In essence, these mechanisms act to make your overall beliefs feel coherent.
Your attitudes affect the strength of your beliefs. That means that the strength of these beliefs changes over time. Because this happens without your awareness, you will not realize that the strength of your beliefs has changed over time. And you will not notice that these beliefs have changed because of your attitudes. Instead, your own experience will just be that everything you can think of fits with your attitude.
If something happens to change your attitude, then that will also change the strength of your beliefs. Deciding you do not like a person so much may make you more aware of his negative characteristics.
The same thing happens with products and even with your beliefs in arguments. For example, the first time you see an iPad, you might be very excited about it. If you decide you want an iPad, then you focus on the desirable properties it has like the number of apps, the ability to bring papers on the road with you, or the opportunity to watch movies when travelling. Less desirable properties may not feel so important at that stage. Someone else who is not that excited about the iPad may focus on the negative characteristics. It is expensive, it requires a subscription to a data network to use it on the road, and many of the apps cost money. For each person, the strength of the beliefs related to the iPad will be influenced by that person's overall attitude toward it.
There is even evidence that these mechanisms are at work in juries making decisions about court cases. Dan Keith Holyoak and Dan Simon studied people playing the role of jurors in a 1999 paper in the Journal of Experimental Psychology: General. They found that as jurors came to believe that someone was guilty, they focused more on evidence consistent with guilt than on evidence consistent with innocence. Conversely, as jurors came to believe that someone was innocent, they relied more on information consistent with innocence than on evidence consistent with guilt.
So, what can you do? For one thing, just knowing that you are wired for coherence can help. Coherence creates a feeling that your beliefs support your attitudes. Coherence will play the strongest role in your attitudes when you rely on feelings to drive your actions. And in many cases, that is fine. It may not be worth over-analyzing your relationship with your friends or simple purchases for yourself or your home.
When decisions are very important, though, it might be worth moving beyond your feelings. If a romantic relationship turns more serious, or if you are called upon to make a big decision (as you would if serving on a jury), then it is worth being a bit systematic about the relationship between your knowledge and your attitudes. Take a more careful look at the things you know that are inconsistent with your attitudes. Any romance or decision that is a good one will withstand a little scrutiny. As it turns out, you can like people without having to like everything about them.
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