80,971 research outputs found

    Change blindness: eradication of gestalt strategies

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    Arrays of eight, texture-defined rectangles were used as stimuli in a one-shot change blindness (CB) task where there was a 50% chance that one rectangle would change orientation between two successive presentations separated by an interval. CB was eliminated by cueing the target rectangle in the first stimulus, reduced by cueing in the interval and unaffected by cueing in the second presentation. This supports the idea that a representation was formed that persisted through the interval before being 'overwritten' by the second presentation (Landman et al, 2003 Vision Research 43149–164]. Another possibility is that participants used some kind of grouping or Gestalt strategy. To test this we changed the spatial position of the rectangles in the second presentation by shifting them along imaginary spokes (by ±1 degree) emanating from the central fixation point. There was no significant difference seen in performance between this and the standard task [F(1,4)=2.565, p=0.185]. This may suggest two things: (i) Gestalt grouping is not used as a strategy in these tasks, and (ii) it gives further weight to the argument that objects may be stored and retrieved from a pre-attentional store during this task

    Visual adaptation to goal-directed hand actions

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    Prolonged exposure to visual stimuli, or adaptation, often results in an adaptation “aftereffect” which can profoundly distort our perception of subsequent visual stimuli. This technique has been commonly used to investigate mechanisms underlying our perception of simple visual stimuli, and more recently, of static faces. We tested whether humans would adapt to movies of hands grasping and placing different weight objects. After adapting to hands grasping light or heavy objects, subsequently perceived objects appeared relatively heavier, or lighter, respectively. The aftereffects increased logarithmically with adaptation action repetition and decayed logarithmically with time. Adaptation aftereffects also indicated that perception of actions relies predominantly on view-dependent mechanisms. Adapting to one action significantly influenced the perception of the opposite action. These aftereffects can only be explained by adaptation of mechanisms that take into account the presence/absence of the object in the hand. We tested if evidence on action processing mechanisms obtained using visual adaptation techniques confirms underlying neural processing. We recorded monkey superior temporal sulcus (STS) single-cell responses to hand actions. Cells sensitive to grasping or placing typically responded well to the opposite action; cells also responded during different phases of the actions. Cell responses were sensitive to the view of the action and were dependent upon the presence of the object in the scene. We show here that action processing mechanisms established using visual adaptation parallel the neural mechanisms revealed during recording from monkey STS. Visual adaptation techniques can thus be usefully employed to investigate brain mechanisms underlying action perception.Publisher PDFPeer reviewe

    Seeing Seeing

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    I argue that we can visually perceive others as seeing agents. I start by characterizing perceptual processes as those that are causally controlled by proximal stimuli. I then distinguish between various forms of visual perspective-taking, before presenting evidence that most of them come in perceptual varieties. In doing so, I clarify and defend the view that some forms of visual perspective-taking are “automatic”—a view that has been marshalled in support of dual-process accounts of mindreading

    Seeing the invisible: The scope and limits of unconscious processing in binocular rivalry

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    When an image is presented to one eye and a very different image is presented to the corresponding location of the other eye, they compete for conscious representation, such that only one image is visible at a time while the other is suppressed. Called binocular rivalry, this phenomenon and its deviants have been extensively exploited to study the mechanism and neural correlates of consciousness. In this paper, we propose a framework, the unconscious binding hypothesis, to distinguish unconscious processing from conscious processing. According to this framework, the unconscious mind not only encodes individual features but also temporally binds distributed features to give rise to cortical representation, but unlike conscious binding, such unconscious binding is fragile. Under this framework, we review evidence from psychophysical and neuroimaging studies, which suggests that: (1) for invisible low level features, prolonged exposure to visual pattern and simple translational motion can alter the appearance of subsequent visible features (i.e. adaptation); for invisible high level features, although complex spiral motion cannot produce adaptation, nor can objects/words enhance subsequent processing of related stimuli (i.e. priming), images of tools can nevertheless activate the dorsal pathway; and (2) although invisible central cues cannot orient attention, invisible erotic pictures in the periphery can nevertheless guide attention, likely through emotional arousal; reciprocally, the processing of invisible information can be modulated by attention at perceptual and neural levels

    Crossing the ‘Uncanny Valley’: Adaptation to Cartoon Faces Can Influence Perception of Human Faces

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    In this study we assessed whether there is a single face space common to both human and cartoon faces by testing whether adaptation to cartoon faces can affect perception of human faces. Participants were shown Japanese animation cartoon videos containing faces with abnormally large eyes. The use of animated videos eliminated the possibility of position-dependent retinotopic adaptation (because the faces appear at many different locations) and more closely simulated naturalistic exposure. Adaptation to cartoon faces with large eyes significantly shifted preferences for human faces toward larger eyes, consistent with a common, non-retinotopic representation for both cartoon and human faces. This supports the possibility that there are representations that are specific to faces yet common to all kinds of faces

    On the Computational Modeling of Human Vision

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    Signals of threat do not capture, but prioritize, attention: a conditioning approach

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    Research suggests that threatening information captures attention more rapidly than neutral information. However, in most studies threat stimuli differ perceptually from neutral stimuli and are instrumental to perform the task, leaving the question unanswered whether threat is sufficient to capture attention. In experiment 1, we designed a visual search task with stimuli of equal salience (colored circles) that have the potential to lead to efficient search (10 ms/item). In experiment 2, one of the colors (conditioned stimulus, CS+) was made threatening by means of fear conditioning. Participants responded to a target presented in one of the circles. Overall, the search was faster on congruent trials (where the target was presented in the CS+) than on baseline trials (where the CS + was absent). Furthermore, the search was slower on incongruent trials (where the target was presented in another color than the CS+) than on baseline trials. The search on congruent trials was affected by set size (90 ms/item), but to a lesser extent than on baseline trials (105 ms/item). We conclude that threat prioritizes, but does not capture attention

    Perceptual Kinds as Supervening Sortals

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    It seems intuitive that in situations of perceptual recognition additional properties are represented. While much has been written about the significance of such properties for perceptual phenomenology, it is still unclear (a) what is the relation between recognition-based properties and lower-level perceptual properties, and (b) whether it is justified to classify them as kind-properties. Relying on results in cognitive psychology, I argue that recognition-based properties (I) are irreducible, high-level properties, (II) are kind properties by virtue of being sortal properties, but (III) they supervene on lower-level properties and so are unlikely to be natural kind properties

    Light environment - A. Visible light. B. Ultraviolet light

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    Visible and ultraviolet light environment as related to human performance and safety during space mission

    Visual adaptation to thin and fat bodies transfers across identity

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    Visual perception is highly variable and can be influenced by the surrounding world. Previous research has revealed that body perception can be biased due to adaptation to thin or fat body shapes. The aim of the present study was to show that adaptation to certain body shapes and the resulting perceptual biases transfer across different identities of adaptation and test stimuli. We designed two similar adaptation experiments in which healthy female participants adapted to pictures of either thin or fat bodies and subsequently compared more or less distorted pictures of their own body to their actual body shape. In the first experiment (n = 16) the same identity was used as adaptation and test stimuli (i.e. pictures of the participant’s own body) while in the second experiment (n = 16) we used pictures of unfamiliar thin or fat bodies as adaptation stimuli. We found comparable adaptation effects in both experiments: After adaptation to a thin body, participants rated a thinner than actual body picture to be the most realistic and vice versa. We therefore assume that adaptation to certain body shapes transfers across different identities. These results raise the questions of whether some type of natural adaptation occurs in everyday life. Natural and predominant exposure to certain bodily features like body shape – especially the thin ideal in Western societies – could bias perception for these features. In this regard, further research might shed light on aspects of body dissatisfaction and the development of body image disturbances in terms of eating disorders
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