S. Nishida and M. Shinya (1998) found that observers have only a limited ability to recover surface-reflectance properties under changes in surface shape. Our aim in the present study was to investigate how the degree of surface-reflectance constancy depends on the availability of information that may help to infer the reflectance and shape properties of surfaces. To this end, we manipulated the availability of (i) motion-induced information (static vs. dynamic presentation), (ii) disparity information (with the levels "monocular," "surface disparity," and "surface + highlight disparity"), and (iii) color information (grayscale stimuli vs. hue differences between diffuse and specular reflections). The task of the subjects was to match the perceived lightness and glossiness between two surfaces with different spatial frequency and amplitude by manipulating the diffuse component and the exponent of the Phong lighting model in one of the surfaces. Our results indicate that all three types of information improve the constancy of glossiness matches--both in isolation and in combination. The lightness matching data only revealed an influence of motion and color information. Our results indicate, somewhat counterintuitively, that motion information has a detrimental effect on lightness constancy.
Psychology moved beyond the stimulus response mapping of behaviorism by adopting an information processing framework. This shift from behavioral to cognitive science was partly inspired by work demonstrating that the concept of information could be defined and quantified (Shannon, 1948). This transition developed further from cognitive science into cognitive neuroscience, in an attempt to measure information in the brain. In the cognitive neurosciences, however, the term information is often used without a clear definition. This paper will argue that, if the formulation proposed by Shannon is applied to modern neuroimaging, then numerous results would be interpreted differently. More specifically, we argue that much modern cognitive neuroscience implicitly focuses on the question of how we can interpret the activations we record in the brain (experimenter-as-receiver), rather than on the core question of how the rest of the brain can interpret those activations (cortex-as-receiver). A clearer focus on whether activations recorded via neuroimaging can actually act as information in the brain would not only change how findings are interpreted but should also change the direction of empirical research in cognitive neuroscience.
We present evidence from asymmetric colour matching experiments which strongly suggests that uniform surrounds evoke induction effects of a very peculiar nature, not representative of colour induction effects in variegated surrounds. Given the widespread use of uniform surrounds in studies of colour vision, this finding is of interest in relation to a number of current research issues, such as contrast coding of colour, functionally equivalent surrounds and colour constancy. A framework that systematises the seemingly complex colour appearance changes induced by uniform surrounds is presented and its implications are discussed.
In a popular magic routine known as “multiplying billiard balls”, magicians fool their audience by using an empty shell that the audience believes to be a complete ball. Here, we present some observations suggesting that the spectators do not merely entertain the intellectual belief that the balls are all solid, but rather automatically and immediately perceive them as such. Our observations demonstrate the surprising potency and genuinely perceptual origin of amodal volume completion.
Variants of Metelli's episcotister model, which are based on additive color mixture, have been found to describe the luminance conditions for perceptual transparency very accurately. However, the findings in the chromatic domain are not that clear-cut, since there exist chromatic stimuli that conform to the additive model but do not appear transparent. We present evidence that such failures are of a systematic nature, and we propose an alternative psychophysical model based on subtractive color mixture. Results of a computer simulation revealed that this model approximately describes color changes that occur when a surface is covered by a filter. We present the results of two psychophysical experiments with chromatic stimuli, in which we directly compared the predictions of the additive model and the predictions of the new model. These results show that the color relations leading to the perception of a homogeneous transparent layer conform very closely to the predictions of the new model and deviate systematically from the predictions of the additive model.
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