Behaviour Change

PROPAGANDA FOR CHANGE is a project created by the students of Behaviour Change (ps359) and Professor Thomas Hills @thomhills at the Psychology Department of the University of Warwick. This work was supported by funding from Warwick's Institute for Advanced Teaching and Learning.

Friday, February 27, 2015

Experts know best!

Toothpaste adverts are known for adverts that use dentists as the main focus to persuade buyers! This advert, published in 2009 shows various people talking about the dentist (expert)’s advice about why they should use Colgate toothpaste. The advert then displays the dentist talking about his expertise, that Colgate is the best choice of toothpaste.

Utilizing a specialist such as a dentist to advertise toothpaste is a very successful advert, because people believe experts. Experts are individuals with specific knowledge in a given domain, in this case a dentist especially knows about teeth and to maintain them. This particular advert works by casting the target in to the role of someone who is “not in the know,” such that the message recipient feels they do not know as much about the topic and subsequently replies on the expert expertise.

Klucharev, Smidts & Fernandez (2008) provide scientific supporting evidence for the expert unknowing public alter cast effect. 24 healthy young females participated in 2 sessions: an FMRI session and a behavioural session separated by 24-30 hours. 180 digital photos of celebrities from music, TV, sport and movies were selected and projected on to screen. Also 360 digital photos of every day products such as cosmetics, clothes and package foods were selected. Products were divided in to 2 conditions, the high expertise condition (celebrity followed by a congruent object such as photo of Andre Agassi followed by a sorts shoe) and low expertise condition (celebrity followed by an incongruent object such as Andre Agassi and an alcohol drink). While being scanned participants were presented with face-object pairs and pressed a button as to whether or not they perceived a link between each celebrity and the object. One-day later participants, objects were presented without the association of expert celebrity and they completed a recognition memory task. Asking subjects to make an estimate of purchase of purchase incidence measured participant’s attitudes. Researchers hypothesized that experts will affect memory and attitude towards the product.

This was exactly what they found, a strong persuasive behavioural effect for experts demonstrated in  Table 1. The effect of expertise on the attitude towards the object was significant t(22, 1) = 3.8, P=0.001. This was due to higher purchase intention for an object that was associated with the expert celebrity (44.3%) status than objects paired with non experts (39.6%). Therefore, researches concluded that this must be because of the high level of celebrity expertise for that object.

To conclude, this empirical research emphases that adverts that associate a product with an expert will increase positives attitudes towards the product, making it more likely the customer will purchase it. In this case, the Colgate advert,  utilising a dentist describing the benefits of the specific tooth paste will persuade potential buyers to invest in their toothpaste.


Klucharev, V., Smidts, A. & Fernadez, G. (2008). Brain mechanisms of persusion: how ‘expert power’ modulates memory and attitudes. Scan, 3, 353-366.

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