Are the effects of attention on speed judgments genuinely perceptual?

A number of studies in recent years have suggested that exogenous and endogenous attention might enhance the perceived magnitude of various perceptual attributes, such as contrast and motion speed. Those studies have generally used comparative judgments as a measure to assess the point of subjective equality; however, similarity judgments have been proposed as possibly less prone to decision biases (Schneider & Komlos, 2008). In three experiments, using a similarity judgment task, we did not find any evidence of motion speed enhancement by exogenous attention. We suggest that the effect revealed by comparative judgments arises at the decisional, rather than the perceptual, stage.