Raita, E. and Oulasvirta, A. (2011) Too good to be bad: Favorable product expectations boost subjective usability ratings. Interacting with Computers, Vol. 23, No. 4, pp. 363-371.
This article studies the effect of positive or negative priming on the subjective usability ratings after the test. The priming was done with two different versions of product review given to the users before starting with the test tasks: one appraising the product, and the other one criticizing it. The difficulty of the test tasks was also manipulated to see, if the effect changes according to the actual performance in the test.
The results showed a very strong effect of positive priming on subjective post-test ratings regardless of the actual performance in the test: Test users who had read a positive review on the system rated the system more positively than the ones with negative review or no review at all. The effect of the type of priming was significant also in the task success with the more difficult test tasks: test users with negative priming completed significantly more tasks than the positively primed.