Lauren N. Hecht

Visual prior entry for foreground figures

Attended stimuli reach perceptual-level processes before unattended stimuli do, a finding that is referred to as visual prior entry. We asked whether a similar effect arises for salient objects (foreground figures) in a visual scene. If prior entry holds for figure—ground perception, targets will be perceived to appear earlier on figures than on grounds. Participants performed a temporal order judgment by reporting the order in which targets appeared. Participants perceived that targets appearing on foreground figures occurred earlier than did those appearing on backgrounds. These findings did not result from a response bias for targets appearing on figures. Most important, when figures and grounds were spatially separated and did not share an edge, no prior-entry effects were observed. Our results suggest that figural regions are available to perceptual-level processes sooner than are grounds.

Attentional Selection of Complex Objects: Joint Effects of Surface Uniformity and Part Structure

What object properties warrant selection by object-based attention? Previous research has suggested that surface uniformity is required for object-based attentional selection (Watson & Kramer, 1999), yet nonuniform objects are encountered frequently. In the present experiments, we investigated the interplay between surface uniformity and part boundaries and their effect on object-based attention. Specifically, we asked if attention can select nonuniform objects whose surface changes occur at part boundaries. Although uniformly colored objects did exhibit object-based effects, we only observed an object-based effect for multicolored objects when surface changes occurred at part boundaries. These findings suggest that attention can only select nonuniform objects when the surface change occurs at a part boundary.

Enhanced spatial resolution on figures versus grounds.

Much is known about the cues that determine figure–ground assignment, but less is known about the consequences of figure–ground assignment on later visual processing. Previous work has demonstrated that regions assigned figural status are subjectively more shape-like and salient than background regions. The increase in subjective salience of figural regions could be caused by a number of processes, one of which may be enhanced perceptual processing (e.g., an enhanced neural representation) of figures relative to grounds. We explored this hypothesis by having observers perform a perceptually demanding spatial resolution task in which targets appeared on either figure or ground regions. To rule out a purely attentional account of figural salience, observers discriminated targets on the basis of a region’s color (red or green), which was equally likely to define the figure or the ground. The results of our experiments showed that targets appearing on figures were discriminated more accurately than those appearing in ground regions. In addition, targets appearing on figures were discriminated better than those presented in regions considered figurally neutral, but targets appearing within ground regions were discriminated more poorly than those appearing in figurally neutral regions. Taken together, our findings suggest that when two regions share a contour, regions assigned as figure are perceptually enhanced, whereas regions assigned as ground are perceptually suppressed.

A dynamic neural field model of temporal order judgments

Temporal ordering of events is biased, or influenced, by perceptual organization-figure-ground organization-and by spatial attention. For example, within a region assigned figural status or at an attended location, onset events are processed earlier (Lester, Hecht, & Vecera, 2009; Shore, Spence, & Klein, 2001), and offset events are processed for longer durations (Hecht & Vecera, 2011; Rolke, Ulrich, & Bausenhart, 2006). Here, we present an extension of a dynamic field model of change detection (Johnson, Spencer, Luck, & Schöner, 2009; Johnson, Spencer, & Schöner, 2009) that accounts for both the onset and offset performance for figural and attended regions. The model posits that neural populations processing the figure are more active, resulting in a peak of activation that quickly builds toward a detection threshold when the onset of a target is presented. This same enhanced activation for some neural populations is maintained when a present target is removed, creating delays in the perception of the targets offset. We discuss the broader implications of this model, including insights regarding how neural activation can be generated in response to the disappearance of information.