Suppose here come two guys, one is gorgeous while one is homely, if you're ladies. And suppose there come two ladies, one is beautiful while the other is not that comely, if you're men. What are your impressions towards them if they do the same thing that counters your discipline or ethics criteria just a little bit?
Of course some of you who are extremely upright will say, "I will dislike all of them if they do so". But I believe that most of us who are just psychological common people will distinguish between them. It seems that we have more endurance and tolerance towards the people with better looking especially who are heterosexual with us.
Having learned the first several chapters, we know that this is due to the halo effect, which is the tendency of ratings of one positive characteristic to "spill over" to influence the ratings of other positive characteristics, and our Belief Perseverance, one of the most profound biases, which refers to our tendency to stick to our initial beliefs even when evidence contradicts them. When we find someone physically attractive, that leads us to have a positive impression on him or her unconsciously. And because of Belief Perseverance, we enhance our positive view about them. Thus, when they did something that counters our belief, we'd have much more endurance and tolerance for them than those who are not as physically attractive as them. In this way, even when evidence comes we'll keep stick to our own belief until the negative evidence is overwhelming.
So although our first impression on people can help us filter what kind of people we're going to meet in most of the times, we should remember that there are a few biases and fallacies that might confuse our views on people. There's a traditional proverb in China, saying "Never measure people by their appearance, and never measure ocean with dou (an old Chinese volume unit)". Knowing this phenomenon we will be more likely to avoid deceptions, and view the world among us more rationally. Although not everyone can come to be a scientist, we do have the ability to think like a scientist, or even better than some of them.