Evolutionary biologists explain that the large frontal cortex in humans, which gives us an exceptional capacity for pattern matching, was originally a survival mechanism. If we're not stronger or faster than our predators, then we need to be able to interpret their signals and make smart choices. Our brains are designed to read meaning into our environment -- whether we're reading gestures, words, sounds, or objects, we are constantly interpreting things, but usually at a level far below our conscious awareness. The top-level interpretations we are aware of are the result of hundreds more subtle patterns we've already decoded. This inherent capacity of the brain explains a lot of understanding that comes to us through intuition, or hunches -- things our conscious mind can't really explain but other levels of our brain have already grasped.
This skill also means that we start to see connections and cause-effect relationships among items that don't necessarily have them. It's a small step from "which one of these things is not like the other" to "when I see round objects I feel happy." Put five items in front of a person and sooner or later you'll start to make judgments about them -- and see connections, comparisons, and relationships that may or may not "be there" at some other level of evaluation. The most beautiful connections we call poetry, metaphor being its most condensed form. The seemingly most obvious connections we might call taste or preference: what seems appealing or disgusting to me seems self-evidently so, yet with a little perspective one realizes that it's just subjective perception. From another angle, we get superstition or mysticism-- human beings are biologically prone to making connections between unrelated things (hence the "lucky socks" students wear to test day) and also therefore prone to mistakes about judging the probability of certain events (any day's news reports gives you plenty of examples).
I've been reading a lot of different material lately about how these pattern matching and judgment skills in the brain operate. (from Blindsight to Fooled by Randomness to Spark.) As a literary critic, I rely upon these skills all the time, and part of my job as a teacher is to help students learn how to become more reflective and critical about the patterns they notice and enjoy. But I've been enjoying trying to observe how often that patterning kicks in -- how frequently I find myself with preferences or assumptions that really don't belong there.
Our oldest dog, known here as Old Girl, likes to eat poop when we're out on a walk. She prefers cat droppings, but will eat other dogs' poop too (but never our own family dogs, never in our own yard -- there's undoubtedly some territorial as well as gustatory element at work in her desire). This is a disgusting habit, but it is almost impossible to completely prevent her from getting some. She's crafty enough to squat to pee -- which is after all one reason for going on the walk -- and then suddenly duck her nose into a pile of cat poop. Old Girl would be approximately 97 years old in human terms, so at some level it's kind of like getting great-granny to give up bacon and cigarettes (that is, if I had such a great granny, but I know people who do). So my walks with Old Girl nearly always involve some struggles over her access to certain stinky items.
Poop is, I think, unequivocally disgusting. Possibly less disgusting than vomit, but I don't really want to put that to the test (and there are lots of digestive variables involved). But then this morning I realized my brain has actually made some more subtle distinctions. Because, I found myself telling Old Girl, cat poop rolled in sandy dirt is MORE disgusting and shouldn't be ingested, even by a poop- and dirt-loving old dog.
Ah, the brain at work. (or something)