This advert from L’Oreal uses the physically attractive-admirer altercast technique. Cheryl Cole is perceived to be an attractive woman and so people want to be part of her world. This need to identify with attractive people can increase persuasion for a product. Therefore, Cheryl is featured in this advert to promote the sales of the shampoo as people want to use the same product in order to be more like her.
This effect is demonstrated by research findings that attractive people as communicators tend to be more effective in selling products (Reingen & Kernan, 1993). In this study, participants were shown photographs of salespersons and recorded their impressions using an impression formation questionnaire. Then they rated each salesperson on a 7-point attractive-unattractive scale. The results showed that buyers tend to treat attractive sellers with more warmth and so are more likely to comply with their requests, compared to unattractive sellers.
Reingen, P. H., & Kernan, J. B. (1993). Social perception and interpersonal influence: Some consequences of the physical attractiveness stereotype in a personal selling setting. Journal of Consumer Psychology, 2, 25-38.