When people stare at a yellow circle and then shift their eyes to a white surface, the afterimage of the circle appears _______________ This phenomenon can best be explained by the _________________ theory of color vision.

The intriguing optical illusion of seeing a color after gazing at its complementary shade has to do with afterimage color perception. This process is closely related to the mechanisms our eyes use to perceive colors. When you stare at a yellow circle, for instance, specific receptors in your eyes are actively responding to yellow. These receptors can become fatigued after prolonged exposure, leading to a diminished response to yellow.

Upon looking away, at a plain white surface, which contains all the colors of the spectrum, the tired receptors for yellow do not respond as vigorously. However, the receptors for the complementary color, which in the case of yellow is blue, are fresh and operate actively. This shift in receptor activity creates the perception of a blue afterimage. The science behind this fascinating visual phenomenon is rooted in the opponent-process theory, which also underlies our understanding of how color vision operates in general.

Explaining how we perceive colors in our environment, the color vision theory plays a crucial role in understanding visual perception. Among the most well-known theories is the opponent-process theory, posited by Ewald Hering in the late 19th century. This theory suggests that our ability to see color is controlled by three opposing systems: blue against yellow, red against green, and black against white.

These pairs work in a see-saw fashion; when one side is stimulated, the other is inhibited. This theory further elucidates why we can't seem to visualize certain color combinations (like 'reddish-green' or 'yellowish-blue') because the idea lies in the impossibility of these opposing pairs being stimulated at the same time. It's the interplay between stimulation and inhibition within these pairs that leads to the rich diversity of colors we perceive, including the explanation for afterimages.

Diving into the psychological aspects of how we comprehend visual information, visual perception psychology is a field that encompasses everything from recognizing shapes and depth to understanding motion and color vision.

Our brains not only interpret signals from our eyes but also fill in gaps and infer details based on context. The opponent-process theory relates to visual perception psychology by suggesting that our perceptions of color are not only physical but heavily influenced by the psychological counterbalance of signals in our brain. After staring at one color for an extended period, the brain anticipates and adjusts to the overstimulation, making the transition to the opposite color in the color pair. This exemplifies how visual perception isn't merely about what occurs in the eye but is very much about how the brain processes the information, often in complex and counterintuitive ways.