Version: v2, Published online: 2010
Retrieved October 19, 2019, from https://www.rep.routledge.com/articles/thematic/vision/v-2
2. Direct versus indirect perception
The claim that visual perception is not direct or immediate involves more than the truism that some processing of the retinal image is necessary to account for what we see. Ideas or perceptions are thought not to be ‘direct’ if they are produced by psychological processes. While the notion of a psychological process admits of no precise definition, examples come readily to mind. Any process that occurs in consciousness, such as the association of ideas, is a psychological process, as is any process that involves learning. Mathematical calculation of distance and size based on the prior representation of lines and angles, whether accessible to consciousness or not, is a psychological process (see Intentionality). Since Berkeley’s theory and the models of the geometric writers both posit psychological processing of the image (albeit of different sorts), they are considered indirect theories of vision.
The difference between direct and indirect accounts of perception is sometimes characterized as a disagreement over the richness of the stimulus, with direct theorists typically arguing that the stimulus contains more information than indirect theorists have been willing to allow. For example, James J. Gibson (1904–79), a prominent direct theorist, claimed that the input to the visual system is not a series of static ‘time slices’ of the retinal image, but rather, the smooth transformations of the optic array as the subject moves about its environment (what Gibson (1979) called ‘retinal flow’). But to characterize the fundamental difference between direct and indirect theories as a disagreement over the richness of the stimulus is to misplace the dispute. The issue that separates the two camps concerns neither the amount of information contained in the stimulus, nor even the precise character of this information, but, rather, how the information in the stimulus is accessed and used by the visual system to produce knowledge that is useful to the organism. In other words, it concerns the character of the intervening processes. Direct theorists deny that visual processes can be characterized in terms of ideas, beliefs, representations, knowledge or memories. In other words, they deny that visual processes have any true psychological description. A direct theory explicates any intervening or supplementary processing that occurs in perception in terms of neural structures and processes directly implemented in the brain. Indirect theorists, of course, do not deny that perceptual processes are implemented in neural structures, but they argue that such processes should be characterized at a distinct, psychological, level of description.
Direct theories of perception are sometimes explicitly contrasted with accounts that treat perception as a species of inference, akin to the drawing of a conclusion from premises according to a principle or rule. The nineteenth-century German physicist and physiologist Hermann von Helmholtz argued that the processes underlying visual perception are of the same general sort as inductive generalization employed in scientific reasoning (see Inductive inference; Inference to the best explanation). We will consider below a contemporary approach modelled on Helmholt’s idea. The perceptual psychologist Irvin Rock (1983) advanced a view that explicitly treats much of perception as a process of hypothesis generation and testing. But the use of ‘inferential’ as a blanket term to refer to indirect theories of perception is somewhat misleading. The various processes that can be thought of as psychological (for example, conscious inference, unconscious calculation, habit-based association, and so on) seem too heterogeneous a collection to justify characterizing the entire class in terms of the drawing of conclusions from antecedently established premises.
Egan, Frances and Nico Orlandi. Direct versus indirect perception. Vision, 2010, doi:10.4324/9780415249126-W047-2. Routledge Encyclopedia of Philosophy, Taylor and Francis, https://www.rep.routledge.com/articles/thematic/vision/v-2/sections/direct-versus-indirect-perception.
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