Specifically, Goodale wants to dissociate perceptual experience from visuomotor action. E.g. in the frog there exist distinct neural pathways for prey-catching and for moving around barriers. In fact, accumulating evidence from studies in both frog and toad suggest that there are at least five separate visual-motor modules, each responsible for a different kind of visually guided behavior and each having distinct input and output pathways. Similar modularity exists in mammals, as shown in studies of rodents. In The Primate Brain Human vision is more complex, and therefore must be more flexible.
Perceptual systems are clearly very different from the simple visuomotor modules of amphibia.
They are not linked to specific motor outputs, but to cognitive systems involving memory, semantics, planning, and communication. The Emergence Of Cortical Visual Systems E.g., saccadic eye movements are carried out by superior colliculus. There is evidence that in the primate brain the outputs from thse basic visuomotor modules and the transfomrations they perform on incoming sensory information can be modified by higher-order input from the cerebral cortex. E.g., saccadic eye movements also involve input from the brain stem. The primitive input-output visuomotor pathways of the early vertebrates, which were little more than simple servomechanisms, have been upgraded to much more subtle control mechanisms capable of mediating the visual guidance of the complex motor outputs that primates are capable of producing.