(Review from my first read)
I consider this book a must-read for anyone interested in the nature of perception. Gibson introduces his theory of ecological affordances and establishes the field of Gibsonian ecological psychology in this book. He theorizes that visual perception consists of affordances, which are opportunities for action that are constituted by the interaction between an animal’s sensorimotor and bodily skills and the material or physical possibilities offered by the environment. His theory entails significances that objects and environmental structures manifest are immediately perceived, rather than inferred or arrived at through some other cognitive process.
Advice for potential readers in approaching this book: Gibson, as a psychologist, is highly readable. However, as a psychologist, many chapters are devoted to small empirical details, some of which are overly speculative and outdated. His overall theory, beyond these small details, remains highly accurate and fruitful for future adaptation and research, however. So, I would recommend that the really essential chapters of this books are the Introduction, "8. The Theory of Affordances," "3. The Meaningful Environment," and "4. The Relationship between Stimulation and Stimulus Information." Other chapters I found theoretically rich are "6. Events and the Information for Perceiving Events," "7. The Optical Information for Self-Perception," and "12. The Theory of Information Pickup and its Consequences".
As a summary of his core theory: Gibson argues that the detail and richness of perceptual experience is not the product of cognitive processes inside the brain. Instead, causal events in the mind-independent environment do much of the “work” in providing potential sensory detail, and an animal simply “samples” these elaborately structured details. Environmental structures and objects have exterior surfaces that reflect light waves, sound waves, and other types of oscillations that occur in transmission mediums, and determine diffraction patterns. Gibson calls these diffraction patterns that fill an animal’s ecological niche an ambient array. There are optic arrays, sonic arrays, and so on.
The textures, sizes, sturdiness, and other compositional features of object surfaces diffract oscillation waves in different manners. The layout of object surfaces in an environmental situation also diffract oscillation waves. There are invariant correspondences between ambient array patterns and types of object surfaces or layouts. Animals are equipped with bodily skills that enable them to “sample” ambient arrays (e.g. visual system accesses arrays of light waves) and directly perceive the particular objects, their unique compositional qualities, and their layout in the environment which determine the patterns in the ambient arrays. These skills are result of an animal species’ evolutionary adaptation in accordance to features of its relevant ecological niche.
Gibson also argues that animal behavior is determined by ecological affordances. Affordances are the opportunities for action inherent in the perception of environmental structures, from the perspective of an animal. For any given animal, the objects that populate its perceptual world are not mere physical structures but necessarily meaningful affordances that express potentialities for action. Animals don’t need to engage in voluntary or complex sensory or cognitive processes in order to figure out how to act in the world; affordances, which are immediately perceived, guide an organism’s behavior.
Objects can be affordances because the particular texture and other compositional features of their surfaces determine the diffraction patterns in the ambient array. The invariant correspondences between compositional feature types and diffraction patterns afford an animal to learn to immediately perceive the compositional features via detection of diffraction patterns. Gibson hypothesizes that because perceptual systems are capable of picking up on these invariant correspondences, they are also capable of picking up on more highly complex invariant correspondences, or “invariant combinations,” such as those between particular emotional effects, functions in sociocultural practices or any number of opportunities of action, and the diffraction patterns determined by particular surface compositional features of objects. Gibson implies that there is a sort of classical conditioning learning process animals undergo in order to gain the embodied skills that can access these more complex invariant combinations and amount to direct perception of the usefulness and significances of objects.
Affordances are neither mind-independent properties of the environment nor properties projected by an organism’s sensory or perceptual systems. Instead, they are the relations between particular aspects of an organism and aspects of its environment. Any mind-independent, material environment has infinite possible ways to be interacted on and manipulated. The particular animal at hand as finite skill sets, which determine the ways it can perceive its ecological niche and interact with it. Any affordance is possible because the material environment permits it, and the animal that perceives this affordance has the particular physiological capacities and learned skills that can access to environment in the relevant ways specified by the affordance.
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(Scattered thoughts from my second read)
Can we just say that there are two ways of defining perception: (1) as consisting in our five sensory modalities, and (2) as whatever (regardless of whether it’s in a sense-datum format) we apprehend, at a personal-level, in an automatic fashion? Only on (2) can we say that we "directly" perceive affordances. Otherwise, if we commit to (1), we could admit that there is subpersonal processing, the drawing of unconscious inferences, that is necessary for synthesizing the experience of affordances; and so when we consider the subpersonal level, and not only the phenomenological level, perception of afforadnces is not direct.
Gibson argues that our perceptual experience consists in both information about the invariant structures of objects and their visual appearances that vary in accordance with our movements in relation to them. The latter claim agrees with our traditional intuitions on what sorts of entities are admissible in perceptual experience: low-level sensory properties. But the former is more troubling. What exact form does the information about invariant structures of objects take on when we consciously encounter it in perception? Nanay might want to say this information is apprehended in the form of mental imagery, which is concurrent with visual appearances of the environment. But this isn’t our only option: perhaps we can think about encountering information that is disembodied of any visual format. But then in what form does this information occur in perception?
So Gibson admits into perception information that is generated by our sensitivity towards what is invariant—that which accounts for the systematic perspectival changes. We can thereby perceive these invariant structures. Given this commitment, what others kinds of information may also permitted for Gibson? Maybe there are embodied skills and internalized social norms that underpin and systematically govern which diverse meanings flow forward (Sartre's “nothingness” in Being and Nothingness); they are available in perceptual experience in an analogous way to invariant physical structures!
Alva Noe claims in Varieties of Presence that objects we could access given our skills show up, even if they're not physically visible. This specification of which feature of an object suffices for it's showing up perceptually is different from Gibson's. What we can access vs. what is invariant and accounting for the systematic changes. Given these different accounts of the conditions that an object needs to meet for it to show up in perception—do these apparently different accounts actually overlap? What are really the correct conditions to be identified—what kinds of objects are admissible in perception, and on what grounds?