Seeing black, white and gray surfaces, called lightness perception, might seem simple because white surfaces reflect 90% of the light they receive while black surfaces reflect only 3%, and the human retina is composed of light sensitive cells. The problem is that, because illumination varies from time to time and from place to place, any amount of light can be reflected from any shade of gray. ...

In the present study, discrete trial familiarization/novelty techniques were used to study lightness constancy in 4-month-old infants. The test stimuli were real objects (paper smiley faces) of two different reflectances, dark gray (17% reflectance) and light gray (54% reflectance). In Experiment 1, the test stimuli were viewed against a white (90% reflectance) surround, and in Experiment 2, ag...

A set of 9-15 colored test fields was presented to goldfish. In Experiment 1, test field hues ranged from green through yellow to red; in Experiment 2, the hues varied from blue through gray to yellow. In the training conditions, the test fields were presented with a gray or black surround. The fish learned to choose one intermediate test field hue by rewarding them with food. In the test condi...

A recent trend in Black German theatre engages with fantasy and posthumanism to criticize racism nationalism. In Krieg der Hörnchen (War of the Squirrels), Simone Dede Ayivi combines postnationalism, using fears invasive gray squirrels taking over habitat native red reimagine xenophobic racist debates about migration.

Glaucoma involves a characteristic optic neuropathy, often with elevated intraocular pressure. Before 1850, poor vision with a normal eye appearance, as occurs in primary open-angle glaucoma, was termed amaurosis, gutta serena, or black cataract. Few observers noted palpable hardness of the eye in amaurosis. On the other hand, angle-closure glaucoma can produce a green or gray pupil, and theref...

Methods for automatic detection of left ventricular endocardium in echocardiograms are required to quantitatively evaluate the functional performance of the left ventricle. This study proposes a new automatic detection method based on ternary thresholding method for echocardiograms. Two thresholds are determined by the discriminant analysis for the gray level histogram so that the input image i...