Advances in neuroscience implicate reentrant signaling as the predominant form of communication between brain areas. This principle was used in a series of masking experiments that defy explanation by feed-forward theories. The masking occurs when a brief display of target plus mask is continued with the mask alone. Two masking processes were found: an early process affected by physical factors such as adapting luminance and a later process affected by attentional factors such as set size. This later process is called masking by object substitution, because it occurs whenever there is a mismatch between the reentrant visual representation and the ongoing lower level activity. Iterative reentrant processing was formalized in a computational model that provides an excellent fit to the data. The model provides a more comprehensive account of all forms of visual masking than do the long-held feed-forward views based on inhibitory contour interactions. From the time a stimulus first enters the eye to the time a percept emerges into consciousness, the initial stimulus has been coded at several levels in the visual system. One of the main goals in studying visual information processing is to specify the representations at each level and the temporal sequence between them (Lachman, Lachman, & Butterfield, 1979). Historically, that sequence was regarded as being mainly feed forward, with processing advancing from simple to increasingly complex attributes, along brain pathways that converge to a common area in which conscious perception occurs. Here, we present an alternative approach, one more in keeping with recent advances in visual neurophysiology. Because we now know that reentrant signals are a major form of communication between brain regions, it is time to begin making explicit use of reentrant processing in theories of perception. To show that this can be done effectively in one domain, we report on a series of psychophysical experiments involving visual masking. In our view, a similar approach could be adopted in other areas of visual perception, especially those in which temporal aspects of processing are at issue.

Identification of the second of two targets is impaired if it is presented less than about 500 ms after the first. Theoretical accounts of this second-target deficit, known as attentional blink (AB), have relied on some form of limited attentional resource that is allocated to the leading target at the expense of the trailing target. Three experiments in the present study reveal a failure of resource-limitation accounts to explain why the AB is absent when the targets consist of a stream of three items belonging to the same category (e.g., letters or digits). The AB is reinstated, however, if an item from a different category is inserted in the target string. This result, and all major results in the AB literature, is explained by the hypothesis that the AB arises from a temporary loss of control over the prevailing attentional set. This lapse in control renders the observer vulnerable to an exogenously-triggered switch in attentional set.

Can four dots that surround, but do not touch, a target shape act as a mask to reduce target discriminability? Although existing theories of metacontrast and pattern masking say “no,” we report this occurs when targets appear in unpredictable locations. In three experiments, a four-dot mask was compared with a standard metacontrast mask that surrounded the target. Although accuracy was predictably different for the two masks at a central display location in Experiment I, both masks had similar strong effects on accuracy in parafoveal locations. Experiment 2 revealed that both four-dot and metacontrast masking were insensitive to contour proximity in parafoveal display locations, and Experiment 3 showed that four-dot masking could occur even at a central location if attention was distributed among several targets. We propose that targets in unattended locations are coded with low spotiotemporal resolution, leaving them vulnerable to substitution by the four dots when attention is directed to them.

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The negative compatibility effect (NCE) is the surprising result that visual targets that follow a brief prime stimulus and a mask can be identified more rapidly when they are opposite rather than identical to the prime. In a recent article in this journal, S. T. Klapp and L. B. Hinkley (2002) proposed that this reflected a competition between inhibitory unconscious processes and excitatory conscious processes. The authors of the current article report 7 experiments with results countering this theory and propose an alternative account within the framework of object substitution masking. In this account, the NCE reflects the updating of perceptual objects, including their links to responses closely associated with those objects.