The Debate Between Dual Visual System Hypothesis And Sensorimotor Theory

How does perceptual experience occur? That is an important question for philosophy of perception. It is generally thought that somewhere in the brain internal representations of the outside world must be set up which, when they are processed, give us the experience. While the enactive view regards perception as active exploration towards the environment. Thus the perceptual experience will not occur without action. The debate between the two views above involves the relationship between perception and action.As to the relationship between perception and action, the dual visual system hypothesis holds that perception is independent of action by showing the separation between perception and action in vision. However, the dual visual system theory fails to explain how the cortical maps, where the retinotopic visual information seems to be organized, can produce rich visual experience about the three-dimensional world. Moreover, the dual visual pathway model offers an inadequate explanation of the interaction between perception and action. In addition, the "experiential blindness" observed in the congenital cataract patients after the removing surgery conflicts with the prediction of the dual visual pathway model. In contrast with the traditional view, Noe’s sensorimotor theory of perception suggests tight interdependence between perception and action and that there will be no formal visual experience without action. To treat perception as active exploration instead of the traditional input-output process can avoid the trouble of dealing the gap between perceptual experience and information processing. Also it can offer a reasonable explanation for the interaction between perception and action, and for "experiential blindness". However, it is still controversial about the interpretation of "experiential blindness".Reviewing the "experiential blindness" and different interpretations respectively from the dual visual system theory and sensorimotor theory, this paper argues that "experiential blindness" provides inadequate support for sensorimotor theory. The dual visual system hypothesis insists that the reason for "experiential blindness" can be found from the aspect of pure sensory deficits, such as the processing of visual information, within the sensory system, and that the possibility of sensory deficit should not be ruled out when discussing the case. Also, Noe’s constitutive hypothesis (COH) fails to offer a better explanation than causal hypothesis (CAH) raised by the traditional view. Hence, as an important evidence for the sensorimotor theory,"experiential blindness" is inadequate.This paper suggests rethinking the debate between sensorimotor theory and the dual visual system hypothesis by clarifying the notion of action. Actually the different accounts for perception derive from different concepts of action. Action and its contribution to perception, in sensorimotor account, only count as the planning stage of action in the dual visual system model. And the exchange of information in the planning stage is an important way of indirect interaction between perception and action, which is different from the direct constitutive role. Noe’s sensorimotor theory is not a threat to the dual visual system theory, and it gives complement to the latter at subpersonal level. By taking the sensorimotor knowledge into the framework of the dual visual system model as a kind of implicit online feedback information, the dual visual pathways model can give better accounts for the generation of visual experience, the cause for "experiential blindness", and the interaction between perception and action. Perception and action are independent, although the perceptual experience needs both explicit information about the visual stimuli and implicit feedback information about the sensorimotor contingencies.