You step off the curb. A horn blares to your left. You step back onto the curb. A good thing, too, you think, as a pick-up truck whizzes by.John Woods, Ralph Johnson, Dov Gabbay & Hans Ohlbach, "Logic and the Practical Turn," in HANDBOOK OF THE LOGIC OF ARGUMENT AND INFERENCE 1, 10 (2002) (vol. 1 in series STUDIES IN LOGIC AND PRACTICAL REASONING, eds., D. Gabbay, J. Siekmann, J. van Benthem & J. Woods).
The "generalization" or generalizations that are at play in such a situation (the one involving the pick-up truck) probably are not exclusively a result of genes. A human being from, say, a remote settlement in a region of the world without automobiles, trucks, and horns might not react exactly the same way if placed in a city and presented with the blare of a horn from a pick-up truck.
But some "reflexive" rules of inference (and resulting actions) may be less dependent on inferential skills developed as a result (in part) of interactions with a specific kind of environment. Consider the "instinctive" ability of the human organism (eye, brain, etc.) to construct a three-dimensional image of, say, a ball when certain certain light signals pass into the human eye and meet the retina. See, e.g., Steven Pinker, "The Mind's Eye," HOW THE MIND WORKS 211-298 (1997); Daniel Chandler, Visual Perception; James Todd, The visual perception of 3D shape (March 2004); P. Tillers, Perceptual Errors. Many such inference rules are so deeply embedded, so to speak, that it is quite hard to know what those rules of inference are. (Sometimes, it is thought, such inference rules do not even exist. But this way of thinking about perception is error.) Consider: human beings often have the ability to distinguish human screams that are generated by fear and terror from human screams that are generated by joy and pleasure. Although it may be possible to figure out how human beings make this distinction -- researchers are hard at work on similar kinds of problems -- it will take much study and research to figure out the rules that human beings use to infer which kind of scream -- fear-inspired or terror-inspired, or some other kind -- they are hearing.
Are explicit generalizations in explicit inferential reasoning a superstructure plunked on top of a submerged iceberg of tacit inference? Or are explicit inference and the generalizations involved in them more autonomous? Fully autonomous? Relatively autonomous? If not always, sometimes? What is the usual relationship between tacit and explicit inference in the sorts of factual problems encountered in legal settings such as trials?
Note: today -- and was it not always so? -- almost all people are familiar with the phenomenon of visual illusions a/k/a optical illusions and other perceptual illusions, perceptual tricks and delusions.
Question: what does the existence of such illusions prove? Answer: not much. The important question, and the hard question, is when visual errors and illusions occur and what if anything we can or should do about them.