No abstract

What role do surface features (e.g., color) play in the establishment and maintenance of episodic representations of objects (object files)? Mitroff and Alvarez (2007) showed that stimuli that were linked by a continuous spatiotemporal history yielded object-specific preview benefits--a standard index of object files-whereas stimuli linked only by shared surface features did not. Here, it is shown that abruptly changing the features of an object that has been established on the basis of spatiotemporal history can disrupt object-specific preview benefits (Experiments 1 and 2). Moreover, under some conditions, feature match alone can give rise to the preview benefits (Experiment 3). These results indicate that surface features, as well as spatiotemporal factors, play an important role in establishing and maintaining episodic object representations.

We live in a dynamic environment in which objects change location over time. To maintain stable object representations the visual system must determine how newly sampled information relates to existing object representations, the correspondence problem. Spatiotemporal information is clearly an important factor that the visual system takes into account when solving the correspondence problem, but is feature information irrelevant as some theories suggest? The Ternus display provides a context in which to investigate solutions to the correspondence problem. Two sets of three horizontally aligned disks, shifted by one position, were presented in alternation. Depending on how correspondence is resolved, these displays are perceived either as one disk "jumping" from one end of the row to the other (element motion) or as a set of three disks shifting back and forth together (group motion). We manipulated a feature (e.g., color) of the disks such that, if features were taken into account by the correspondence process, it would bias the resolution of correspondence toward one version or the other. Features determined correspondence, whether they were luminance-defined or not. Moreover, correspondence could be established on the basis of similarity, when features were not identical between alternations. Finally, the stronger the feature information supported a certain correspondence solution the more it dominated spatiotemporal information.

How is the visual system able to maintain object identity as the objects or the eyes move? While many early studies have shown small or no influence of feature information on this correspondence process, more recent studies have shown large feature effects. Here we investigated if this incongruity might be due to the distance over which the feature influence has an effect. We used a variation of the Ternus display (Ternus, 1926), an ambiguous apparent motion display, in which two sets of three discs are presented and one can perceive either three discs moving together (group motion) or one disc jumping across the other two discs (element motion). We biased the percept toward element motion by matching the features of some of the discs. In Experiment 1, with the three discs aligned and moving vertically, we added a horizontal offset between the two sets of discs and found a strong bias toward element motion that decreased with increasing spatial offset. In Experiment 3 participants had to make horizontal saccades across the same Ternus displays so that the two Ternus frames were horizontally offset on the retina, but not in spatiotopic coordinates. We found that the bias showed a similar spatial range, but now it was clear that the range was set in spatial coordinates independently of the retinal position. These results show that feature information contributes to correspondence over a limited spatial range (Experiment 1) and that the range is imposed in spatial, not retinal, coordinates (Experiment 2).

Recently, Yeshurun and Levy (Psychol Sci 14:225-231, 2003) have provided evidence for the notion that visual attention impairs the temporal resolution of the visual system. Specifically, the detection of a temporal gap within a visual stimulus was impaired when a cue directed attention towards the spatial location of the stimulus. As this negative cueing effect is important to constrain theories about visual attention, we further investigated this novel effect and assessed whether it truly reflects an attentional effect. Experiment 1 examines whether the negative cueing effect is due to local temporal interference, and Experiments 2 and 3 investigate whether it reflects a luminance confound. The complete pattern of results argues against these alternatives and thus further strengthens the conclusion of Yeshurun and Levy (Psychol Sci 14: 225-231, 2003).

Transient spatial attention refers to the automatic selection of a location that is driven by the stimulus rather than a voluntary decision. Apparent motion is an illusory motion created by stationary stimuli that are presented successively at different locations. In this study we explored the effects of transient attention on apparent motion. The motion target presentation was preceded by either valid attentional cues that attract attention to the target location in advance (experiments 1-4), neutral cues that do not indicate a location (experiments 1, 3, and 4), or invalid cues that direct attention to a non-target location (experiment 2). Valid attentional cues usually improve performance in various tasks. Here, however, an attentional impairment was found. Observers' ability to discriminate the direction of motion diminished at the cued location. Analogous results were obtained regardless of cue type: singleton cue (experiment 1), central non-informative cue (experiment 2), or abrupt onset cue (experiment 3). Experiment 4 further demonstrated that reversed apparent motion is less likely with attention. This seemingly counterintuitive attentional degradation of perceived apparent motion is consistent with several recent findings, and together they suggest that transient attention facilitates spatial segregation and temporal integration but impairs spatial integration and temporal segregation.

Responses to targets that appear at a noncued position within the same object (invalid-same) compared to a noncued position at an equidistant different object (invalid-different) tend to be faster and more accurate. These cueing effects have been taken as evidence that visual attention can be object based (Egly, Driver, & Rafal, Journal of Experimental Psychology: General, 123, 161-177, 1994). Recent findings, however, have shown that the object-based cueing effect is influenced by object orientation, suggesting that the cueing effect might be due to a more general facilitation of attentional shifts across the horizontal meridian (Al-Janabi & Greenberg, Attention, Perception, & Psychophysics, 1-17, 2016; Pilz, Roggeveen, Creighton, Bennet, & Sekuler, PLOS ONE, 7, e30693, 2012). The aim of this study was to investigate whether the object-based cueing effect is influenced by object similarity and orientation. According to the object-based attention account, objects that are less similar to each other should elicit stronger object-based cueing effects independent of object orientation, whereas the horizontal meridian theory would not predict any effect of object similarity. We manipulated object similarity by using a color (Exp. 1, Exp. 2A) or shape change (Exp. 2B) to distinguish two rectangles in a variation of the classic two-rectangle paradigm (Egly et al., 1994). We found that the object-based cueing effects were influenced by the orientation of the rectangles and strengthened by object dissimilarity. We suggest that object-based cueing effects are strongly affected by the facilitation of attention along the horizontal meridian, but that they also have an object-based attentional component, which is revealed when the dissimilarity between the presented objects is accentuated.

To maintain stable object representations as our eyes or the objects themselves move, the visual system must determine how newly sampled information relates to existing object representations. To solve this correspondence problem, the visual system uses not only spatiotemporal information (e.g., the spatial and temporal proximity between elements), but also feature information (e.g., the similarity in size or luminance between elements). Here we asked whether motion correspondence relies solely on image-based feature information, or whether it is influenced by scene-based information (e.g., the perceived sizes of surfaces or the perceived illumination conditions). We manipulated scene-based information separately from image-based information in the Ternus display, an ambiguous apparent-motion display, and found that scene-based information influences how motion correspondence is resolved, indicating that theories of motion correspondence that are based on "scene-blind" mechanisms are insufficient.