1 When something positive happens
When a person believes that a positive thing has happened he might feel like touching his eyebrows. This behavior happens on the unconscious level and most people won't be aware of the reason they are doing it. (See also why do people touch their noses while speaking)
2 When a person sees something he likes
If a person sees someone he likes, he might feel like touching his eyebrows. Because this is considered a positive situation, the subconscious mind of the person might let him touch his eyebrows. (see the body language of attraction)
3 When the person hears something he likes
If a person hears something that appeals to him, he might touch his eyebrows. In such a case, the gesture will happen right after the person hears the phrase that appealed to him.
4 When a person gets a positive thought
If a person gets a positive or an optimistic thought, he will feel like touching his eyebrows. A person can do this gesture even if he is sitting alone (See why are some people pessimistic)
5 When a negative situation ends
A person can make that gesture right after a negative situation ends. If someone is stuck in a traffic jam, he might make that gesture as soon as the traffic eases up.
6 Touching can happen often if many positive things happen
A person can touch his eyebrows more than once in a very short period of time if more than one positive thing happens or if a very positive thing happens.
7 When a person sees something he likes
If a person sees something he likes such as his new good looking car, he might feel like touching his eyebrows.
8 When a person goes through a positive situation
If a person performs well in a presentation or goes through any positive situation, he might feel like touching his eyebrows either during the situation or after it.