“In vision, grouping refers to the way in which elements in the visual world combine or stay separate from one another in our mental image of the world. Grouping is partly an automatic process, which means that much of it happens rapidly in our brains and without our conscious awareness. It has been described simply as the problem of ‘what goes with what’ in our visual field. Hermann von Helmholtz, the nineteenth century scientist who taught us much of what we now accept as the foundations of auditory science, described it as an unconscious process that involved inferencing, or logical deductions about what objects in the world are likely to go together based on a number of feature or attributes of the objects.
If you are standing on a mountaintop overlooking a varied landscape, you might describe seeing two or three other mountains, a lake, a valley, a fertile plain, and a forest.
Although the forest is composed of hundreds or thousands of trees, the trees form a perceptual group, distinct from other things we see, not necessarily because of our knowledge of forests, but because the trees share similar properties of shape, size, and color — at least when they stand in opposition to fertle plains, lakes, and mountains.
But if you are in the center of a forest with a mixture of alder trees and pines, the smooth white bark of the alders will cause them to ‘pop out’ as a seperate group from the craggy dark-barked pines.
If I put you in front of one tree and ask you what you see, you might start to focus on details of that tree: bark, branches, leaves (or needles), insects, and moss.
When looking at a lawn, most of us don’t typically see individual blades of grass, although we can if we focus our attention on them.
Grouping is a hierarchical process and the way in which our brains form perceptual groups is a function of a great many factors.
Some grouping factors are intrinsic to the objects themselves — shape, color, symmetry, contrast, and principles that address the continuity of lines and edges of the object. Other grouping factors are psychological, that is mind based, such as what we’re consciously trying to pay attention to, what memories we have of this or similar objects, and what our expectations are about how objects should go together.”
This is you brain on music P. 75