Final answer:
The peculiar visual disabilities described in the question, where stroke victims lose the capacity to perceive motion or color while retaining other visual abilities, illustrate the normal capacity of our visual system to process different visual features independently.
Step-by-step explanation:
The peculiar visual disabilities described in the question are examples of visual deficits that occur following a stroke. Some stroke victims lose the capacity to perceive motion but retain the capacity to perceive shapes and colors, while others lose the capacity to perceive colors but retain the capacity to perceive movement and form. These disabilities provide evidence for the normal capacity of our visual system to process different visual features independently.
For example, the loss of motion perception but retained shape and color perception suggests that motion processing occurs in a separate pathway from shape and color processing. This is known as parallel processing, which refers to the simultaneous processing of multiple aspects of a visual scene by different neural pathways.
In contrast, the loss of color perception but retained motion and form perception suggests that color processing occurs in a separate pathway from motion and form processing. This is supported by evidence from studies of patients with visual deficits caused by brain damage, which have identified specific brain regions responsible for processing different visual features, such as motion, color, and shape.