Have you been in situations where we judge a person by the type of clothes he wears and his appearance? You might refuse to share your belongings with a person wearing ragged clothes but when the same help is asked by a well dressed person your reaction may be opposite. Ever thought if such reflexes are simply human tendencies or is there some scientific outlook to this?
Such a situation when a trait of a person or a thing is used to make an overall judgement is termed as "halo effect". It is a socio-psychological phenomenon that causes people to be biased in their judgments by transferring their feelings about an attribute of something to other attributes. You yourself might have experienced that a tall or good looking person will be perceived as being intelligent and trustworthy even though there is no logical reason to believe that height or looks correlate with smartness and honesty.
There is a belief that the first impression is the last impression. But it is when you spend time with a person that you come to know him. So Halo effect, most of the times, leads us to make wrong judgements.
But halo effect,many a times, has positive impacts on organizations, locations, products and communication channels. If users have a bad experience with a site they predict that the site will treat them poorly in the future as well and thus will be reluctant to return to the site. Hence its important to keep the halo effect in mind while planning sites or designing flows because dropoffs at any one point in your users experience may indicate a poor "first impression". So designers these days are making the interface more visually appealing.
Isn't it astonishing that such merely noticed reactions of ours can have a scientific root which can also be exploited for betterment of technology!?