Final answer:
Binocular rivalry is the binocular phenomenon characterized by periodic/intermittent extinction of brightness or form from perception when orthogonally oriented targets are presented simultaneously to both eyes.
Step-by-step explanation:
The binocular phenomenon characterized by periodic/intermittent extinction of brightness or form from perception when orthogonally oriented targets are presented simultaneously to both eyes is called binocular rivalry. Binocular rivalry occurs when different images are presented to each eye, resulting in the brain's inability to fuse the two images into a single percept. This causes the perception to alternate between the two images, with each image disappearing intermittently from perception. For example, if a red image is presented to one eye and a green image to the other eye, the perception may alternate between seeing only the red image and only the green image, or a combination of both.