Final answer:
Visual illusions are C. physical stimuli that consistently produce errors in perception due to the active processing of visual signals by the brain and the eye's signal processing, often creating a perception that doesn't match physical measurements.
Step-by-step explanation:
Visual illusions, also known as optical illusions, are physical stimuli that consistently produce errors in our perception of the world. These illusions occur because of the complex interactions between our visual system and the brain, creating perceptions that do not match the physical reality.
For instance, a checkerboard with seemingly non-parallel lines can be an illusion where, despite the lines being parallel, our brain's interpretation makes them appear otherwise. Our brains do not simply capture images like a camera; instead, they actively process visual information to construct a stable and coherent view of the world around us. This processing can lead to errors in perception, as demonstrated by illusions.
Even our perceptions of color and brightness are affected by context, as with the checkerboard illusion where our brain adjusts hues to compensate for shadows, leading to perceived differences in square colors. Notably, through signal processing in the eye and brain adjustments, our visual system fills in blind spots and adapts to changed visual fields, like inverting prism glasses experiments, further illustrating the brain's active role in perception.