Selectivity of face aftereffects for expressions and anti-expressions.

Adapting to a facial expression can alter the perceived expression of subsequently viewed faces. However, it remains unclear whether this adaptation affects each expression independently or transfers from one expression to another, and whether this transfer impedes or enhances responses to a different expression. To test for these interactions, we probed the basic expressions of anger, fear, happiness, sadness, surprise, and disgust, adapting to one expression and then testing on all six.

Simulations of adaptation and color appearance in observers with varying spectral sensitivity.

A model of adaptation and visual coding was used to simulate how color appearance might vary among individuals that differ only in their sensitivity to wavelength. Color responses to images were calculated for cone receptors with spectral sensitivities specific to the individual, and in postreceptoral mechanisms tuned to different combinations of the cones. Adaptation was assumed to normalize sensitivity within each cone and postreceptoral channel so that the average response to an ensemble of scenes equaled the mean response in channels defined for the reference observer.

Visual discomfort and natural image statistics.

Images with excessive energy at medium spatial frequencies (Fernandez and Wilkins, 2008 Perception 37 1098-1113), or that have high color contrast and little or no luminance contrast (Wilkins et al, 2008 Perception 37 Supplement, 144-145) appear uncomfortable or aversive and can induce headaches in hypersensitive observers. Such stimuli are uncharacteristic of natural images, and we examined whether visual discomfort more generally increases with deviations from the spatial and chromatic properties of natural scenes. Observers rated the level of discomfort or artistic merit in color images generated from noise or random overlapping rectangles (Mondrians).

Foreshortened tiles in paths converging on an observer viewing a picture: elevation and visual angle ratio determine perceived size.

Observers were shown wide-angle pictures of tiles on a ground plane and were asked about the aspect ratios of the tiles. The observers viewed the pictures from a fixed center of projection. Some of the tiles were in a path coming straight toward the observer.

Variations in normal color vision. V. Simulations of adaptation to natural color environments.

Modern accounts of color appearance differ in whether they assume that the perceptual primaries (e.g., white and the unique hues of red, green, blue, and yellow) correspond to unique states determined by the spectral sensitivities of the observer or by the spectral statistics of the environment.

Ellipses on the surface of a picture.

Shapes on the surface of a perspective picture may be misperceived. Subjects picked a match for an ellipse depicting the circular top of a cylinder. The top was depicted as tilted forward from 5 degrees to 85 degrees, generating a series of ellipses on the picture surface.

Angle illusion on a picture's surface.

Shapes on picture surfaces are not seen accurately (Arnheim, 1954). In particular, if they depict 3-D forms, angles between lines on a picture surface are misperceived. To test four theories of the misperception, subjects estimated acute and obtuse internal angles of quadrilaterals.

Blind man draws using diminution in three dimensions.

Can the principle of convergence in three spatial dimensions be reflected in drawings by the congenitally blind? A man who had been totally blind since birth was asked to draw scenes such as a tabletop with three cubes receding to the observer's left side. He used converging lines to show the tops of the cubes receding in depth. He drew the cubes to the left smaller than the cube in front of the observer.

Looking at perspective pictures from too far, too close, and just right.

A central problem for psychology is vision's reaction to perspective. In the present studies, observers looked at perspective pictures projected by square tiles on a ground plane. They judged the tile dimensions while positioned at the correct distance, farther or nearer.

Foreshortening, convergence and drawings from a blind adult.

Esref is a congenitally totally blind man, practiced in drawing. He was asked to draw solid and wire cubes situated in several places around his vantage point. He used foreshortening of receding sides and convergence of obliques, in approximate one-point perspective.

Looking for inhibition of return in pigeons.

We conducted four experiments in order to investigate whether pigeons' responses to a recently attended (i.e., recently pecked) location are inhibited.

Haptics and projection: drawings by Tracy, a blind adult.

Outline drawings in a raised form were made by a blind woman, Tracy, who has been blind from very early in life. Highly practiced in drawing, she reports she is largely self-taught. To invoke matters of projection, she was asked to represent an object with faces slanting away from the observer, a fixed array from different vantage points, and sets of objects in depth.