Advertisements use celebrity endoresement to grab the audiences attention straight away as people watching the advert are most likely well aware of the celebrity featuring in the advert. I think when the viewers see a celebrity in an advert they automatically watch the advert as they will presume the product that is being advertised by the celebrity is also used by the celebrity and is of a high quality.
An example of an advert using celebrity endoresement is the L'Oreal shampoo advert. This features the singer, Cheryl Cole.
Cheryl Cole is obviously really famous and girls and women aspire to be like her and see her as a role model so her doing this would have a great beneficical effect on the L'oreal shampoo. Females will think their hair will look like hers if they use the product she does.
