What evidence is there that implicit reaction time tests can predict anything that explicit methods can’t?

In terms of the predictive validity of implicit versus explicit methods, there are numerous examples in the peer-reviewed literature demonstrating that in many circumstances (including in the case of consumer choice) implicit attitudes are better predictors of subsequent behaviour than explicit responses provided at the same time.  For example, Steinman and Karpinski (2008) found that implicit but not explicit attitudes towards the brand GAP predicted GAP patronage and buying intentions. Brunel, Tietje and Greenwald (2004) showed that implicit methods can detect attitudes about brands that explicit measures cannot (e.g., the effects of the same or different race of the advocates of a brand).

Other research highlights the subtleties of attitudes that implicit methods are able to detect that are missed by explicit methods. For example, Priluck and Till (2009) found that explicit and implicit measures were both good at detecting attitudinal differences between brands when the difference was large or obvious, but only implicit methods could detect differences when they are less obvious. Other research shows that implicit methods in a consumer context are difficult to fake - Chan and Sengupta (2010) found that while the claims of an advertisement were dismissed, implicit responses revealed favourable attitudes to the brand.

A very convincing study of the benefits of assessing implicit attitudes is from Vianello et al. (2010) in which college students were given explicit and implicit measures of conscientiousness. Half were further told to imagine that they were being tested for their ideal job (good income, low effort, and so on) and half were not. Those with the job-story had higher explicit measures of conscientiousness (showing that they could give biased answers), but both groups scored about the same on the implicit measure – which shows that the implicit measure was not easy to fake.