As in my previous post, I’m at page 40 of Gibson’s book.
Gibson’s view is that we need to understand our environment to understand vision. The environment in which we (and other animals) live is not arbitrary, it has its own rules and structure. Gibson therefore devotes a large part of his book to describing our environment, which he insists differs from the abstract worlds of physics and geometry. The environment is what we perceive from the physical world, it has its own logics.
It’s very entertaining to read Gibson’s description of our environment. It starts from scratch, as if the world around us had to be explained to an alien being. The result appears either as the work of a madman or of a genius.
Interestingly, Gibson’s description of the environment bears uncanny resemblances with how we would specify a virtual environment in a 3D modelling language. There is a ground plane, light sources, surfaces, vertices, edges, interiors and exteriors, textures. Perhaps we shouldn’t be surprised that a psychologist who seeks to describe how we visually experience the real world and a programmer who wants to create a language for simulating this very experience end up with similar primitives. There are important differences, of course. Gibson rejects Cartesian coordinates, emphasizes the irregularity and complexity of the world, and introduces many more entities and concepts.
Yet if Gibson had to design a 3D modelling language, it would almost certainly be based on shell models rather than solid geometry. He is obsessed with surfaces. Surfaces are of uttermost importance, it is where the action is, he writes. Granted, virtually all the sensory information we gather from objects (visual, olfactory and tactile) come from their surface. But if the goal is really to describe how we experience the world, then perhaps there should be a greater focus on volumes.
If I cut an apple in two, two new surfaces appear to me, but I am not surprised at all. Unless there is something weird (e.g., the apple is rotten, or there’s a worm inside), I don’t get much extra information from cutting it, i.e., there is no surprise. This means I was experiencing the apple as a solid, full object in the first place. Throughout our lives we have accumulated an extensive experience in cutting things such as meat or fruits, and breaking things such as rocks or sticks. While some objects are certainly hollow, many are full and solid. We know that, and this is how we experience most objects even if we can’t directly see inside.
As some philosopher puts it (I can’t recall whom), when I look at a tomato, I experience the redness of the tomato on its entire surface, not only on the part that’s facing me. Most likely, we also experience the redness inside the tomato.
When we hold an object, we also perceive its mass. It is conveyed through the object’s surface, but it depends on what’s inside. The mass of an object (or similarly, its density) is a crucial information in many tasks. It decides on how much force we will apply to an object when we grab it. It is also a crucial piece of information when we need to throw an object such as a rock, an example Gibson mentions himself.
Either Gibson was not aware of this, or more likely, his model of the environment is not meant to be fully phenomenal, i.e., it is not meant to directly capture our subjective experience of the world. After all, we certainly don’t experience things as abstract as optic ambient arrays. It’s already challenging to understand what these things mean. Rather, Gibsons’ constructs seem to lie somewhere between the phenomenal world and the physical world. They form a layer of abstraction on top of the phenomenal world, that can help explain the phenomenal world.