The speed and accuracy of material recognition in natural images

We studied the time course of material categorization in natural images relative to superordinate and basic-level object categorization, using a backward-masking paradigm. We manipulated several low-level features of the images—including luminance, contrast, and color—to assess their potential contributions. The results showed that the speed of material categorization was roughly comparable to the speed of basic-level object categorization, but slower than that of superordinate object categorization. The performance seemed to be crucially mediated by low-level factors, with color leading to a solid increase in performance for material categorization. At longer presentation durations, material categorization was less accurate than both types of object categorization. Taken together, our results show that material categorization can be as fast as basic-level object categorization, but is less accurate.     

Attentional involvement in subitizing: Questioning the preattentive hypothesis

Subitizing, the rapid, effortless, and accurate enumeration of small numbers of items has been said to be carried out preattentively. If so, the preattentive processing could occur entirely in primary visual cortex, in which case it would be completed within about 50 ms, or during the feedforward sweep, in which case it would be completed within about 100 ms after the onset of an enumeration display which was followed by a mask. The stimulus–mask SOAs were 50 or 83 ms in Experiment 1, and 100 or 150 ms in Experiment 2. In both experiments subjects were more accurate and more sensitive to one-target than to two-target displays. These outcomes, in conjunction with the finding that accuracy and sensitivity were higher at the longer SOA, are inconsistent with the preattentive viewpoint and point to the necessity for attentional involvement in subitizing.     

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.