This advert is for the bank Halifax, and is used to show that the bank will give its customers £5 each month if they have a certain type of account. For some reason, however, rather than trying to instil a sense of trust into potential customers (which one feels is vital for a firm that a person intends to look after their money), they portray the employees as people more interested in having a joke than actually doing their job. In conjunction with this, all of the employees are of average to low attractiveness. The overall effect of this is that the actors in the advertisement have low source-credibility.
Sharma (1990) demonstrated that when a message was presented by a person with low source-credibility, the content of the message isn’t remembered as well, and is not processed as deeply. To assess this they manipulated the experience (2 years or 6 months working in the establishment) and education (Degree or high school) of the salesperson. In the high credibility condition there was higher reported buying intentions, and higher reported trustworthiness of the salesperson.
Sharma, A. (1990). The persuasive effect of salesperson credibility: conceptual and empirical examination. The Journal of Personal Selling and Sales Management, 71-80.