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Crowding is unlike ordinary masking: Distinguishing feature detection and integration
- Journal of Vision
, 2001
"... A letter in the peripheral visual field is much harder to identify in the presence of nearby letters. This is called "crowding". In general, masking is a procedure: introducing any "mask" pattern that affects discriminability of the signal. Crowding conforms to the masking paradi ..."
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Cited by 88 (2 self)
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A letter in the peripheral visual field is much harder to identify in the presence of nearby letters. This is called "crowding". In general, masking is a procedure: introducing any "mask" pattern that affects discriminability of the signal. Crowding conforms to the masking paradigm, but the crowding effect is unlike ordinary masking. Here we characterize crowding, and present diagnostic tests that distinguish it from ordinary masking. In ordinary masking, the signal disappears. In crowding, it remains visible, but is ambiguous, confounded with its neighbors. Masks are usually effective only if they overlap the signal, but the crowding effect extends over a large region. The width of that region is proportional to signal eccentricity from the fovea and independent of signal size, mask size, signal and mask font, and number of masks. At 4 deg eccentricity, the threshold contrast for identification of a 0.32 deg signal letter is elevated (up to six-fold) by mask letters anywhere in a 2.3 deg region, seven times wider than the signal. In ordinary masking, threshold contrast rises as a power function of mask contrast, with a shallow log-log slope of 0.5 to 1, while in crowding, threshold is a sigmoidal function of mask contrast, with a steep log-log slope of 2 at close spacing. Most remarkably, although the threshold elevation decreases exponentially with spacing, the threshold and saturation contrasts of crowding are independent of spacing. Finally, ordinary masking is similar for detection and identification, but crowding occurs only for identification, not detection. More precisely, crowding occurs only in tasks that cannot be done based on a single detection by coarsely coded feature detectors. These results (and observers' introspections) suggest that ordinary masking b...
Failures of retrieval and comparison constrain change detection in natural scenes
- Journal of Experimental Psychology: Human Perception and Performance
, 2003
"... In a change detection paradigm, a target object in a natural scene either rotated in depth, was replaced by another object token, or remained the same. Change detection performance was reliably higher when a target postcue allowed participants to restrict retrieval and comparison processes to the ta ..."
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Cited by 49 (8 self)
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In a change detection paradigm, a target object in a natural scene either rotated in depth, was replaced by another object token, or remained the same. Change detection performance was reliably higher when a target postcue allowed participants to restrict retrieval and comparison processes to the target object (Experiment 1). Change detection performance remained excellent when the target object was not attended at change (Experiment 2) and when a concurrent verbal working memory load minimized the possibility of verbal encoding (Experiment 3). Together, these data demonstrate that visual representa-tions accumulate in memory from attended objects as the eyes and attention are oriented within a scene and that change blindness derives, at least in part, from retrieval and comparison failure. People spend most of their waking lives within environments that typically contain a great deal of visual detail and many constituent objects. The visual complexity of natural environments necessitates selective visual processing of local scene regions by movements of the eyes and attention (see Henderson & Holling-worth, 1998, 1999a).1 Figure 1 shows a typical eye movement scan pattern on a scene during 20 s of viewing. Note that the eyes
In Defense of Abstractionist Theories of Repetition Priming and Word Identification
"... There is a great deal of interest in characterizing the representations and processes that support visual word priming and written word identification more generally. On one view, these phenomena are supported by abstract orthographic representations that map together visually dissimilar exemplars o ..."
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Cited by 37 (1 self)
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There is a great deal of interest in characterizing the representations and processes that support visual word priming and written word identification more generally. On one view, these phenomena are supported by abstract orthographic representations that map together visually dissimilar exemplars of letters and words (e.g., the letters A/a map onto a common abstract letter code a*). On a second view, orthographic codes consist in a collection of episodic representations of words that interact in such a way that it sometimes looks as if there are abstract codes. P.L. Tenpenny (1995) contrasted these general approaches, and concluded by endorsing the episodic account, arguing that no evidence demands that we posit abstract orthographic representations. This review re-considers the evidence, and argues that a variety of priming and non-priming research strongly supports the conclusion that abstract orthographic codes exist and support priming and word identification. On this account, episodic representations are represented separately from abstract orthographic knowledge, and contribute minimally to these functions. In defense of abstractionist theories of repetition priming and word identification There is a great deal of interest in characterizing the representations and processes that support the improved processing of stimuli repeated during an experiment; the so-called repetition priming effect. Indeed, two different types of repetition priming have been intensively studied from two quite different perspectives. On the one hand, researchers interested in memory have tended to focus on long-term repetition priming, in which facilitation can last minutes, hours, and sometimes longer (Sloman, Hayman, Ohta, Law, & Tulving, 1988). For example, participants are generally f...
fMRI activity patterns in human LOC carry information about object exemplars within category
- J. Cogn. Neurosci
, 2008
"... & The lateral occipital complex (LOC) is a set of areas in the human occipito-temporal cortex responding to objects as opposed to low-level control stimuli. Conventional functional magnetic resonance imaging (fMRI) analysis methods based on regional averages could not detect signals discriminati ..."
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Cited by 35 (4 self)
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& The lateral occipital complex (LOC) is a set of areas in the human occipito-temporal cortex responding to objects as opposed to low-level control stimuli. Conventional functional magnetic resonance imaging (fMRI) analysis methods based on regional averages could not detect signals discriminative of different types of objects in this region. Here, we examined fMRI signals using multivariate pattern recognition (support vector classification) to systematically explore the nature of objectrelated information available in fine-grained activity patterns in the LOC. Distributed fMRI signals from the LOC allowed for above-chance discrimination not only of the category but also of within-category exemplars of everyday man-made objects, and such exemplar-specific information generalized across changes in stimulus size and viewpoint, particularly in posterior subregions. Object identity could also be predicted from responses of the early visual cortex, even significantly across the changes in size and viewpoint used here. However, a dissociation was observed between these two regions of interest in the degree of discrimination for objects relative to size: In the early visual cortex, two different sizes of the same object were even better discriminated than two different objects (in accordance with measures of pixelwise stimulus similarity), whereas the opposite was true in the LOC. These findings provide the first evidence that direct evoked fMRI activity patterns in the LOC can be different for individual object exemplars (within a single category). We propose that pattern recognition methods as used here may provide an alternative approach to study mechanisms of neuronal representation based on aspects of the fMRI response independent of those assessed in adaptation paradigms. &
A Theory of Eye Movements During Target Acquisition
"... The gaze movements accompanying target localization were examined via human observers and a computational model (target acquisition model [TAM]). Search contexts ranged from fully realistic scenes to toys in a crib to Os and Qs, and manipulations included set size, target eccentricity, and target–di ..."
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Cited by 35 (10 self)
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The gaze movements accompanying target localization were examined via human observers and a computational model (target acquisition model [TAM]). Search contexts ranged from fully realistic scenes to toys in a crib to Os and Qs, and manipulations included set size, target eccentricity, and target–distractor similarity. Observers and the model always previewed the same targets and searched identical displays. Behavioral and simulated eye movements were analyzed for acquisition accuracy, efficiency, and target guidance. TAM’s behavior generally fell within the behavioral mean’s 95% confidence interval for all measures in each experiment/condition. This agreement suggests that a fixed-parameter model using spatiochromatic filters and a simulated retina, when driven by the correct visual routines, can be a good general-purpose predictor of human target acquisition behavior.
Encoding multielement scenes: Statistical learning of visual feature hierarchies
- Journal of Experimental Psychology: General
, 2005
"... The authors investigated how human adults encode and remember parts of multielement scenes composed of recursively embedded visual shape combinations. The authors found that shape combinations that are parts of larger configurations are less well remembered than shape combinations of the same kind t ..."
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Cited by 34 (6 self)
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The authors investigated how human adults encode and remember parts of multielement scenes composed of recursively embedded visual shape combinations. The authors found that shape combinations that are parts of larger configurations are less well remembered than shape combinations of the same kind that are not embedded. Combined with basic mechanisms of statistical learning, this embeddedness constraint enables the development of complex new features for acquiring internal representations efficiently without being computationally intractable. The resulting representations also encode parts and wholes by chunking the visual input into components according to the statistical coherence of their constituents. These results suggest that a bootstrapping approach of constrained statistical learning offers a unified framework for investigating the formation of different internal representations in pattern and scene perception.
Object categorization: Reversals and explanations of the basic-level advantage
- Journal of Experimental Psychology: General
, 2007
"... People are generally faster and more accurate to name or categorize objects at the basic level (e.g., dog) relative to more general (animal) or specific (collie) levels, an effect replicated in Experiment 1 for categorization of object pictures. To some, this pattern suggests a dual-process mechanis ..."
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Cited by 31 (2 self)
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People are generally faster and more accurate to name or categorize objects at the basic level (e.g., dog) relative to more general (animal) or specific (collie) levels, an effect replicated in Experiment 1 for categorization of object pictures. To some, this pattern suggests a dual-process mechanism, in which objects first activate basic-level categories directly and later engage more general or specific categories through the spread of activation in a processing hierarchy. This account is, however, challenged by data from Experiment 2 showing that neuropsychological patients with impairments of conceptual knowledge categorize more accurately at superordinate levels than at the basic level—suggesting that knowledge about an object’s general nature does not depend on prior basic-level categorization. The authors consider how a parallel distributed processing theory of conceptual knowledge can reconcile the apparent discrepancy. This theory predicts that if healthy individuals are encouraged to make rapid categorization responses, the usual basic general advantage should also reverse, a prediction tested and confirmed in Experiment 3. Implications for theories of visual object recognition are discussed.
Sustained change blindness to incremental scene rotation: A dissociation between explicit change detection and visual memory
- Perception & Psychophysics
, 2004
"... this paper, we will argue that despite these failures of explicit change detection, participant's visual memory representation of the scene was nevertheless sensitive to the difference between views. Specifically, consecutive views of the scene were compared, and although the difference between ..."
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Cited by 25 (4 self)
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this paper, we will argue that despite these failures of explicit change detection, participant's visual memory representation of the scene was nevertheless sensitive to the difference between views. Specifically, consecutive views of the scene were compared, and although the difference between views was not sufficient to yield explicit change detection, it was sufficient to update memory to reflect the changed viewpoint. Before directly examining whether memory was updated to reflect recent views (Experiment 2), it is important to eliminate two alternative explanations for the poor explicit change detection performance in Experiment 1. First, changes may have been missed because participants simply failed to construct or retain a representation from a previous view (O'Regan, 1992). Second, it could be that a representation of the previous view was retained across the masked interval, but it was immediately overwritten by perceptual processing of the next view, without comparison of the two views (Rensink et al., 1997)
How Visual Cortex Recognizes Objects: The Tale of the Standard Model
, 2002
"... A host of experimental data has been accumulating on the properties and mechanisms of object recognition in cortex. We review the main findings, and summarize them using a quantitative, biologically plausible, Standard Model. The model is a tool to interpret and understand the available data, and ..."
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Cited by 23 (4 self)
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A host of experimental data has been accumulating on the properties and mechanisms of object recognition in cortex. We review the main findings, and summarize them using a quantitative, biologically plausible, Standard Model. The model is a tool to interpret and understand the available data, and generate questions and predictions for new experiments.
Robust visual servoing
- International Journal of Robotics Research (IJRR
, 2003
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