The influence of arm posture on the Uznadze haptic aftereffect.

The role of arm posture in the Uznadze haptic aftereffect is investigated: two identical test stimuli (i.e., spheres, TS) clenched simultaneously appear haptically different in size after hands have been adapted to two spheres (adapting stimuli, AS) differing in size: the hand adapted to a small AS feels TS bigger than the hand adapted to a big AS.

The Poggendorff illusion in Ruben's Descent from the Cross in Antwerp: Does the illusion even matter?

Two experiments are described, the purpose of which was to investigate the presence of a misalignment illusion caused by Poggendorff-like conditions in two paintings by Peter Paul Rubens, both depicting the , one located in Antwerp (Belgium), the other in Lille (France). The first shows a geometrical misalignment made by Rubens in a minor detail, which is considered proof that the artist observed the Poggendorff illusion. The second painting, instead, shows a perfect geometrical alignment in a similar detail.

Looking Into Mona Lisa's Smiling Eyes: Allusion to an Illusion.

We present results from two experiments aimed at studying the direction of 's gaze and its affective expression. In experiment 1 we studied the effect of retinal image size on the perception of her gaze by manipulating observation distances of a high-quality print of the painting. Participants ( = 30) were asked to answer a simple question (is the person portrayed looking at you?) from six different distances ranging from 55 to 755 cm.

See What You Feel: A Crossmodal Tool for Measuring Haptic Size Illusions.

The purpose of this research is to present the employment of a simple-to-use crossmodal method for measuring haptic size illusions. The method, that we call , was tested by employing Uznadze's classic haptic aftereffect in which two spheres physically identical (test spheres) appear different in size after that the hands holding them underwent an adaptation session with other two spheres (adapting spheres), one bigger and the other smaller than the two test spheres. To measure the entity of the illusion, a three-dimensional visual scale was created and participants were asked to find on it the spheres that corresponded in size to the spheres they were holding in their hands out of sight.

The Stroop-matching task as a tool to study the correspondence effect using images of graspable and non-graspable objects.

The Stroop-matching task is a variation of the Stroop task in which participants have to compare a Stroop stimulus attribute (color or word) to a second stimulus. The Stroop-matching response conflict (SMRC) represents an interference related to the processes involved in selection/execution of manual responses. In the present study, we developed a variation of the Stroop-matching task in which the Stroop stimuli were matched to graspable objects (a cup) with intact or broken handles laterally oriented (Experiment 1) or to colored bars laterally presented (Experiment 2).

The Influence of Physical Illumination on Lightness Perception in Simultaneous Contrast Displays.

Three experiments investigated the role of physical illumination on lightness perception in simultaneous lightness contrast (SLC). Four configurations were employed: the classic textbook version of the illusion and three configurations that produced either enhanced or reduced SLC. Experiment 1 tested the effect of ambient illumination on lightness perception.

Food perception at lunchtime does not depend on the nutritional and perceived characteristics of breakfast.

Breakfast consumption can entail nutritional advantages positively affecting food choices. This study investigated the effect of minor changes in breakfast composition on the perceived attributes of foods, both at breakfast and at lunchtime. Four breakfasts were defined considering nutritional and perceptual factors.

The Poggendorff illusion before Poggendorff.

This paper is about the Poggendorff illusion in pictorial artworks. In particular, it deals with the role played by the Poggendorff illusion in the making of the geometrical misalignments in the mosaic known as Lunetta di San Lorenzo in Ravenna (Italy) and in Rubens's oil on panel Descent from the Cross in Antwerp (Belgium). Three experiments are presented.

Mishaps, errors, and cognitive experiences: on the conceptualization of perceptual illusions.

Although a visual illusion is often viewed as an amusing trick, for the vision scientist it is a question that demands an answer, which leads to even more questioning. All researchers hold their own chain of questions, the links of which depend on the very theory they adhere to. Perceptual theories are devoted to answering questions concerning sensation and perception, but in doing so they shape concepts such as reality and representation, which necessarily affect the concept of illusion.

The size illusion and lightness contrast effect in Delboeuf-like displays: possible evidence of percept-percept coupling.

We conducted two experiments to test the relationship between Delboeuf's size-contrast illusion and a concomitant lightness contrast effect that can be observed when achromatic disks are employed as targets. In experiment 1 participants were asked to adjust the diameter of a target (D1) surrounded by a small circular size-inducer (C1) to match in size a comparison target (D2) surrounded by a circular size-inducer (C2) either equal or greater in diameter than C1. Experiment 2 was similar to experiment 1, except that D1 and D2 were physically equal in size, and participants were asked to adjust the luminance of D1 to match D2 in lightness.

Lightness effects in Delboeuf and Ebbinghaus size-contrast illusions.

We examined lightness effects observed in Delboeuf and Ebbinghaus size-contrast illusions. Results of four experiments are reported. Experiment 1 was conducted with Delboeuf-like stimuli and shows that the disk that appears bigger appears either lighter or darker than the disk that appears smaller, depending on the contrast polarity between disks and background.

Illusory lightness in the Delboeuf figure.

A white disk presented inside a small concentric circle (a display like the Delboeuf figure) looks lighter than when inside a larger one. The magnitude of the effect was measured with 20 observers (10 women, 10 men; ages 19 to 26 years). The decrements in luminance of the disk inside the smaller circle, in order to match the lightness of the disk inside the larger circle, are reported for three different grey backgrounds and correspond to 9.

Measuring the meter: on the constancy of lightness scales seen against different backgrounds.

The constancy of a 16-step achromatic Munsell scale was tested with regards to background variations in two experiments. In experiment 1 three groups of observers were asked to find lightness matches for targets in simultaneous lightness displays by using a 16-step achromatic Munsell scale placed on a white, black, or white-black checkered background. In experiment 2, a yellow-blue checkered background and a green-red checkered background replaced Munsell scales on the black and on the white backgrounds.

San Lorenzo and the Poggendorff illusion in Ravenna.

In the Mausoleum of Galla Placidia (Ravenna, Italy), the San Lorenzo lunette shows two peculiar visual effects: a transparency effect of gold seen through gold and perceptual collinearity between two parts of a cross which are physically misaligned. Both effects are found within the area of the halo surrounding the saint's head. In this work we addressed the problem posed by the physical misalignment of the cross.

When figure-ground segmentation modulates brightness: the case of phantom illumination.

In the phantom illumination illusion, luminance ramps ranging from black to white induce a brightness enhancement on an otherwise homogeneous dark background. The strength of the illusion was tested with regard to the extension of the brightness inducing perimeter, surrounding the target area by manipulating the number of inducers (exp. 1) and the size of the inducers (exp.