Biomedical subjects

T Agostini

Publications and source records attributed to T Agostini.

7 recordsLinked to original sources

PubMed1999

An anchoring theory of lightness perception.

A review of the field of lightness perception from Helmholtz to the present shows the most adequate theories of lightness perception to be the intrinsic image models. Nevertheless, these models fail on 2 important counts: They contain no anchoring rule, and they fail to account for the pattern of errors in surface lightness. Recent work on both the anchoring problem and the problem of errors has produced a new model of lightness perception, one that is qualitatively different from the intrinsic image models. The new model, which is based on a combination of local and global anchoring of lightness values, appears to provide an unprecedented account of a wide range of empirical results, both classical and recent, especially the pattern of errors. It provides a unified account of both illumination-dependent failures of constancy and background-dependent failures of constancy, resolving a number of long-standing puzzles.

Gestalt Theory↗

PubMed1999

Spatial articulation affects lightness.

In a recent paper, Agostini and Bruno (1996) showed that the size of simultaneous lightness contrast increases under Gelb lighting. To extend Agostini and Bruno's work, we applied their methodology to a set of more spatially articulated displays. In four experiments, we investigated the role of spatial articulation on the size of the simultaneous lightness contrast effect. In the first experiment, we found a decrease of the simultaneous lightness contrast effect as the spatial articulation increased. In the second experiment (the control experiment), performed under homogeneous illumination, we found that the effect of spatial articulation is not detectable, even though the data seem to show the same trend as that in the previous experiment. In the third experiment, we found that spatial articulation affects not only the middle reflectance region, but also the lowest one. As the spatial articulation increases, the effect on the lightnesses of both regions decreases. In the last experiment, performed with a reduced range of reflectances, we found a lightening effect for all the reflectances and, again, an effect of spatial articulation. The results of these experiments are interpreted according to the model proposed by Gilchrist et al. (in press).

Humans↗

PubMed1998

The trajectory of a dot crossing a pattern of tilted lines is misperceived.

The straight trajectory of a dot crossing a pattern of tilted lines is perceived as being sinusoidal. Manipulation of the size of the angle between the trajectory and the tilted lines, the velocity of the dot, and the distance between the tilted lines shows that the magnitude of the illusion is inversely proportional to the size of the incidence angle, to velocity, and to the distance between the lines. The illusion is interpreted as being the result of an integration process of local distortions occurring at the intersections with the tilted lines.

Humans↗

PubMed1997

One-tube method for complete HPA-1 genotyping by PCR using sequence-specific primers.

Human platelet antigens (HPA) can be targets for antibody responses that cause life-threatening thrombocytopenia following platelet transfusions or pregnancy. As an aid to diagnosis and prevention, serologic and DNA-based methods have been developed to type HPA. Of the DNA-based strategies, those using the polymerase chain reaction (PCR) are very sensitive, but often require processing of amplification products. Sequence-specific primers (SSP) in the PCR eliminate the need for extensive handling of reaction products beyond gel electrophoresis. However, current methods require a separate reaction for each allele being typed. In this report we describe a method to simultaneously and completely genotype both alleles of HPA-1 in a single PCR. In addition, because the absence of an amplification product might also show the failure of a SSP, we introduced a recombinant template that can only be amplified by the SSP, thus ensuring primer performance and the identified genotype.

Alleles↗

PubMed1996

Lightness contrast in CRT and paper-and-illuminant displays.

The increased use of CRT monitors for displaying and controlling stimuli in studies of surface color poses problems of comparability with data obtained with traditional paper-and-illuminant methods. A review of comparable studies using the two methodologies revealed that CRT studies tend to report larger contrast effects. To investigate factors that may be responsible for this difference, simultaneous lightness contrast was measured using both CRT and paper-and-illuminant presentations. The spatial distribution of luminance in the whole field of view and the visual angles subtended by the displays were controlled. The CRT presentation yielded contrast effects twice as big as those measured for a paper surface in a homogeneously illuminated room. However, a paper display under Gelb lighting yielded almost exactly the same effect size as that measured in the CRT presentation. These results demonstrate that contrast effects in both modes of presentation are affected by the spatial distribution of luminance beyond the basic experimental stimuli.

Adult↗

PubMed1994

Müller-Lyer illusion and perception of numerosity.

Illusion of numerosity can be observed in many of the classical illusions of linear extent by replacing the uninterrupted lines with rows of dots. Using the method of constant stimuli both length and numerosity illusions move in the same direction, whereas using a magnitude-estimation method the two illusions move in opposite directions. Two experiments show that this inversion occurs also in the Müller-Lyer illusion.

Attention↗

PubMed1993

Perceptual organization evokes simultaneous lightness contrast.

Principles of perceptual organization can cause simultaneous lightness contrast to be seen in patterns in which the inducing regions are not proximal to the target. In three experiments a match was made between two grey targets, one of which belonged to a white perceptual grouping and the other to a black one. In experiment 1, perceived belongingness was a product of common fate and figural alignment (columns of black dots and columns of white dots moved up and down in counterphase). In experiment 2, belongingness was evoked with only figural alignment. In experiment 3, belongingness was induced by common fate alone. In all three experiments it was found that the grey target belonging to the white group appeared darker than the grey target belonging to the black group.

Adult↗