Beliefs alter holistic face processing ... if response bias is not taken into account.

The composite paradigm is widely used to quantify holistic processing (HP) of faces, but there is debate regarding the appropriate design (partial vs. complete) and measures in this task. Here, we argue that some operational definitions of HP are problematic because they are sensitive to top-down influences, even though the underlying concept is assumed to be cognitively impenetrable. In Experiment 1, we told one group of participants that the target face half would remain the same on 75% of trials and another group that it would change on 75% of trials. The true proportion of same/different trials was 50%-groups only differed in their beliefs about the target halves. In Experiment 2, we manipulated the actual proportion of same/different trials in the experiment (75% of trials were the same for one group; 75% of trials were different for another group) but did not give explicit instructions about proportions. In both experiments, these manipulations influenced response biases that altered partial design measures of HP while the complete design measure was unaffected. We argue that the partial design should be abandoned because it has poor construct validity.