Halo Effect vs. Horn Effect
The Halo Effect is a very relevant concept in society that many forget about. The Halo Effect is when positive immediate evaluations about a person (e.g. she is likable) bleed over into judgments about their specific traits (e.g. she is likable, therefore she is also intelligent).
Hollywood stars demonstrate the Halo Effect perfectly. Because they are often attractive and likable, we naturally assume they are also intelligent, friendly, trustworthy, and so on. When a celebrity endorses an item, our positive opinion of that individual can move on to impacting our perceptions of the product itself.
Conversely, The Horn Effect is typically when a negative immediate evaluation about a person (e.g he looks unkempt) influences our judgment of more detailed traits (e.g. he looks unkempt, therefore he must be dumb). This effect tends to come into play in everyday settings. Whether it be school, work, or in the grocery store, we make these quick assumptions subconsciously. We use these impressions to further our relationships with people, or to refrain from ever building a relationship with them.