When Categories Collide Accumulation of Information About Multiple Categories in Rapid Scene Perception (original) (raw)
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Issues concerning selective attention provoke new questions about visual segmentation, and vice-versa. We illustrate this by describing our recent work on grouping under conditions of inattention, on change blindness for background events and the residual processing of undetected background changes, on modal versus amodal completion in visual search, and the differential effects of these two forms of completion on attentional processes, and on attentional modulation of lateral interactions thought to arise in early visual cortex. Many of these results indicate that segmentation processes substantially constrain attentional processes, but the reverse influence is also apparent, suggesting an interactive architecture. We discuss how the ‘proto-objects’ revealed by studies of segmentation and attention (i.e. the segmented perceptual units which constrain selectivity) may relate to other object-based notions in cognitive science, and we wrestle with their relation to phenomenal visual awareness.
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Journal of Experimental Psychology: …, 2005
Studies have suggested attention-free semantic processing of natural scenes in which concurrent tasks leave category detection unimpaired (e.g., F. Li, R. VanRullen, C. Koch, & P. . Could this ability reflect detection of disjunctive feature sets rather than high-level binding? Participants detected an animal target in a rapid serial visual presentation (RSVP) sequence and then reported its identity and location. They frequently failed to identify or to localize targets that they had correctly detected, suggesting that detection was based only on partial processing. Detection of targets was considerably worse in sequences that also contained humans, presumably because of shared features. When 2 targets were presented in RSVP, a prolonged attentional blink appeared that was almost eliminated when both targets were detected without being identified. The results suggest rapid feature analysis mediating detection, followed by attention-demanding binding for identification and localization.
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The extent to which object identification is influenced by the background of the scene is still controversial. On the one hand, the global context of a scene might be considered as an ultimate representation, suggesting that object processing is performed almost systematically before scene context analysis. Alternatively, the gist of a scene could be extracted sufficiently early to be able to influence object categorization. It is thus essential to assess the processing time of scene context. In the present study, we used a go/no-go rapid visual categorization task in which subjects had to respond as fast as possible when they saw a ''man-made environment'', or a ''natural environment'', that was flashed for only 26 ms. ''Man-made'' and ''natural'' scenes were categorized with very high accuracy (both around 96%) and very short reaction times (median RT both around 390 ms). Compared with previous results from our group, these data demonstrate that global context categorization is remarkably fast: (1) it is as fast as object categorization [Fabre-Thorpe, M., Delorme, A., Marlot, C., & Thorpe, S. (2001). A limit to the speed of processing in ultra-rapid visual categorization of novel natural scenes. Journal of Cognitive Neuroscience, 13(2), 171-180]; (2) it is faster than contextual categorization at more detailed levels such as sea, mountain, indoor or urban contexts [Rousselet, G. A., Joubert, O. R., & Fabre-Thorpe, M. (2005). How long to get to the ''gist'' of real-world natural scenes? Visual Cognition, 12(6), 852-877]. Further analysis showed that the efficiency of contextual categorization was impaired by the presence of a salient object in the scene especially when the object was incongruent with the context. Processing of natural scenes might thus involve in parallel the extraction of the global gist of the scene and the concurrent object processing leading to categorization. These data also suggest early interactions between scene and object representations compatible with contextual influences on object categorization in a parallel network.
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What information is available from a brief glance at a novel scene? Although previous efforts to answer this question have focused on scene categorization or object detection, real-world scenes contain a wealth of information whose perceptual availability has yet to be explored. We compared image exposure thresholds in several tasks involving basic-level categorization or global-property classification. All thresholds were remarkably short: Observers achieved 75%-correct performance with presentations ranging from 19 to 67 ms, reaching maximum performance at about 100 ms. Global-property categorization was performed with significantly less presentation time than basic-level categorization, which suggests that there exists a time during early visual processing when a scene may be classified as, for example, a large space or navigable, but not yet as a mountain or lake. Comparing the relative availability of visual information reveals bottlenecks in the accumulation of meaning. Understanding these bottlenecks provides critical insight into the computations underlying rapid visual understanding.
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This article advances a framework that casts object recognition as a process of discrimination between alternative object identities, in which top-down and bottom-up processes interact-iteratively when necessary-with attention to distinguishing features playing a critical role. In two experiments, observers discriminated between different types of artificial fish. In parallel, a secondary, variable-SOA visual-probe detection task was used to examine the dynamics of visual attention. In Experiment 1, the fish varied in three distinguishing features: one indicating the general category (saltwater, freshwater), and one of the two other features indicating the specific type of fish within each category. As predicted, in the course of recognizing each fish, attention was allocated iteratively to the distinguishing features in an optimal manner: first to the general category feature, and then, based on its value, to the second feature that identified the specific fish. In Experiment 2, two types of fish could be discriminated on the basis of either of two distinguishing features, one more visually discriminable than the other. On some of the trials, one of the two alternative distinguishing features was occluded. As predicted, in the course of recognizing each fish, attention was directed initially to the more discriminable distinguishing feature, but when this feature was occluded, it was then redirected to the less discriminable feature. The implications of these findings, and the interactive-iterative framework they support, are discussed with regard to several fundamental issues having a long history in the literatures on object recognition, object categorization, and visual perception in general.
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The perceptual relations between wholes and their component parts have been a controversial issue for psychologists and philosophers before them. The question is whether processing of the overall structure precedes and determines the processing of the component parts or properties, or whether the component properties are registered first and are then synthesized to form the objects of our awareness. There have been two opposite approaches to this issue: the early feature-analysis view and the holistic primacy view. According to the prevailing early feature-analysis view, perceptual processing begins with the analysis of simple features and elements that are later integrated into coherent objects. In this chapter, I present empirical findings that challenge this view, showing holistic primacy in different perceptual tasks and early in the course of perceptual processing.
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Shape Perception in Human and Computer Vision, 2013
In this chapter, we review our research demonstrating that object perception is a dynamical, integrated process in which (a) high-level memory representations are accessed before objects are perceived; (b) potential objects compete for perception and only the winners are perceived; and (c) there is no clear dividing line between perception and memory. Our review begins with results that led us to reject the traditional serial hierarchical view of object perception as well as modern versions in the form of feedforward processing models. We then outline the accumulating evidence that led us to favor a more dynamical, interactive model that involves feedforward as well as feedback processing between high-and low-levels of the visual hierarchy. In our review, we highlight how our views changed over time.