If you like the president’s politics, you probably like his voice and his appearance as well. The tendency to like (or dislike) everything about a person–including things you have not observed–is known as the halo effect. The term has been in use in psychology for a century, but it has not come into wide use in everyday language. This is a pity, because the halo effect is a good name for a common bias that plays a large role in shaping our view of people and situations. It is one of the ways the representation of the world that system one generates is simpler and more coherent than the real thing.
You meet a woman named Joan at a party and find her personable and easy to talk to. Now her name comes up as someone who could be asked to contribute to a charity. What do you know about Joan's generosity? The correct answer is that you know virtually nothing, because there is little reason to believe that people who are agreeable in social situations are also generous contributors to charities. But you like Joan and you will retrieve the feeling of liking her when you think of her. You also like generosity and generous people. By association, you are now predisposed to believe that Joan is generous. And that you believe she is generous you probably like Joan eve better than you did earlier, because you have added generosity to her pleasant attributes.
The sequence in which we observe characteristics of a person is often determined by chance. Sequence matters, however, because the halo effect increase the weight of the first impressions, sometimes to the point that subsequent information is mostly wasted.
Daniel Kahneman, Thinking, Fast and Slow