Perceiving the world of real objects seems so easy that it is difficult to grasp just how complicated it is. Not only do we need to construct the objects quickly, the objects keep changing even though we think of them as having a consistent, independent existence (Feldman, 2003). Yet, we usually get it right, there are few failures. We can perceive a tree in a blinding snowstorm, a deer bounding across a tree line, dodge a snowball, catch a baseball, detect the crack of a branch breaking in a strong windstorm amidst the rustling of trees, predict the sounds of a dripping faucet, or track a street musician strolling down the road. In all cases, the sensations must be split into that part that gives information about real objects that may change in shape, sound, timing, or location and that part that gives information about the random or non-predictable parts of the background. The object becomes âin front ofâ the background.
The light energy at the eyes, the sound energy at the ears, and the pressure sensations on hands are neutral. Moreover, the light energy at each eye is two-dimensional due to the âflat screenâ structure of the retina, the sound energy at each ear has only a weak spatial component, and the pressure sensations must be integrated to yield the surfaces of objects. For all three senses, the energy must be interpreted to give the properties of the three-dimensional objects and events in the world.
Perception is not passive. Looking at, listening to, sneaking a peek, eavesdropping, rubbing, fingering, shaking, and grasping are all actions that ultimately yield information about objects. But these acts just give us the energy at the receptor, they do not by themselves specify a particular object. Many different objects could produce those same sensations. It is the creative and intentional act of looking or listening that results in the construction of objects (Handel, 2006). Perceptions are not independent of the perceiver . The sensory receptors of all organisms limit what can be known about the real world. It might be too strong to argue that we can never perceive the true physical world, but those limitations act to mark off the consequential features. Perceiving is basically focusing on parts of the environment so that depending on their objectives, expectations , and knowledge, people often end up with different outcomes (Felin, Koenderink, & Krueger, 2017).
1.1 The Aperture and Correspondence Problem
Many constraints limit our ability to perceive objects, whether memory or cognitive limitations or environmental obstacles. Auditory, visual, and tactual sensations are constantly changing, and a visual glimpse, auditory snippet, or brief touch must be interpreted in terms of what preceded it in time and space and what will follow it. This has been termed the aperture problem to convey the idea that it is like looking through a slit or hole. While this term is couched in visual terms, it obviously also is true for auditory and tactual events that naturally evolve in time and space. The aperture problem is both the cause and a complement to the correspondence problem. The sensations at any one instance cannot unambiguously signify objects or events; consequently, the perceptual systems must integrate sensations across time and space to achieve a stable world of objects. This has been termed the binding problem âwhat sensations go with which objects (Burwick, 2014).
The correspondence problem comes in many guises, but the fundamental issue is whether objects or events that occur at different positions, orientations, shapes, intensities, pitches, rhythms, and so on represent the reoccurrence of the same object or represent a different one. I imagine that the observer constructs a trajectory that can link the sensations that occur at different locations and times. Some of these transformations could be predictable (geometrically) particularly for rigid objects. These trajectories or transformations link objects in different orientations, at different pitches, and at different rhythms.
I was driving home one night and noticed two headlights at the same height coming towards me, and naturally assumed that they were mounted on one car, but then the headlights diverged. My first reaction, it was in the 1960s when the TV show Candid Camera was extremely popular, that this was a stunt: it was a rubber car or at least a car that was able to shift the position of its headlights. Actually it was two similar motorcycles moving relative to each other. Given my assumption that it was one car, I expected the lights to change position relative to each other based on the geometric properties of rigid bodies, and groped for an explanation when that expectation failed. It is worth noting that I finally realized that they were two motorcycles by the exhaust sounds. Perceiving almost always involves more than one sense. This will be a constant theme in all chapters.
Other transformations would not be as predictable since instruments and singers do not sound alike at widely different pitches and baby pictures do not undergo predictable change as they become adult pictures. Nonetheless, all of these transformations would bind together those pictures or sounds that stem from one object and segregate those that stem from different ones. The correspondence problem asks whether the âbefore and afterâ visual, auditory, and tactual sensations come from the same object. This correspondence might be easy to determine for a single bouncing ball due to its visual trajectory and impact sounds, but it would be much harder to determine which notes correspond to each violinist in an orchestra from the bowing movements.
What this means is that cognitive and physiological constraints along with the uncertainty of the sensory stimulation require the perceptual system to make use of assumptions based on prior experiences with objects in the world in order to perceive accurately. Otherwise, because the sensations could not always correctly make out objects, the world would be ambiguous (Pizlo, 2001). The transformation of the visual, auditory, or tactual sensations into objects depends on many stages and processes at every physiological level. Interactions transform the sensations at the individual receptors in the eye, ear, or hand into information. Cells in the eye, ear, or hand merely respond to energy at different frequencies and pressures. It is the receptive fields in the visual system based on combinations of retinal cells that respond to edges that simultaneously bound objects and separate them from others, it is receptive fields in the auditory system that respond to frequency glides that are characteristic of the sound of many objects (Hubel & Weisel, 1962), and it is interactions of sensors in the skin and muscle that give rise to shape and texture. Further processing isolates the predictable ways objects change over space and time and that predictability shapes our ability to make the world coherent.
The iOS game app Shadow...