Perceptual integration of motion and form information: is the movement filter involved in form discrimination?

Seven experiments reinvestigated J. Driver and P. McLeod's (1992) report of a "visual search asymmetry reversal" in a task that required the integration of motion and form information. They found that, when the form discrimination was easy, search was more efficient for a moving rather than a stationary conjunction target; the reverse was true when form discrimination was difficult. J. Driver and P. McLeod proposed that 2 mechanisms are involved: a "stationary form system," which supports accurate form discrimination but is relatively insensitive to movement, and a "movement filter," which segregates the moving from the stationary items but is relatively insensitive to aspects of form. The present experiments failed to find the asymmetry reversal. The results agree with the (more parsimonious) proposal that the function of the movement filter is limited to separating moving from stationary items, whereas form discrimination is accomplished within a unitary form system.