"Effortless" texture segmentation and "parallel" visual search are not the same thing

If a region composed of one set of texture elements is effortlessly perceived on a background composed of another set, the texture segmentation is said to occur "preattentively". If the time required to find a target item among distractor items is independent of the number of distractor items, the visual search is said to occur with all items processed "in parallel". Effortless, preattentive texture segmentation and parallel visual search are sometimes assumed to be equivalent measures of the same parallel processing stage in the visual system. The demonstrations presented here show that this is not the case. Parallel processing can occur with stimuli that do not support effortless texture segmentation and vice versa.