Gibson? need to look up more of his work

**Visual perception is the study of the mapping from perceptible external objects, through optic information that represents them, to the observer who uses that information for his or her purposes. Geometry is the vehicle of this instillation. Not only is geometry useful in describing the object, encoding it in equations for the purposes of description by the experimenter, but also, I suggest, observers can decode that information along lines which demonstrate that the human visual system is a sophisticated geometry-analyzing machine.

**Information is shaped by the mutuality of the perceiver and environment.

**Information, I claim, is found in the geometric relations of parts of objects to each other and to their surrounds. Rules of geometry govern these relations presented to a perceiver, and it is the discovery of those rules papplicable to visual perception that is a major psychological task.

**Nonetheless, some questions of a metaphysical nature show more promise from an approach rooted in empirical psychology…What is the nature of information such that it informs us? This question is at the intersection of psychology, philosophy, and artificial intelligence. An answer to it is, I contend, a necessary beginning to any account of perception.

sense data - unanalyzed sensations from sense organs as sent to the central nervous system

internal representation - common and useful to all fields of cognitive science, not as important here

**Proper consideration of external representation is logically prior to internal representation and information processing; we must know what information is used before we can understand how it is processed

*The study of perceptual information needs a methodology.

**Information for a perceiver is not in frequency, intensity, mass, extent, or time; it is distributed across them.

**Although distortions can be found in static cross sections of the optic array, they seem less noticeable (or less disruptive) in dynamic images. There, movement of the observer, motions of an object, or both reveal three-dimensional relations. Projective geometry is the body of rules for that revelation, and the perceptual system appears to know some of them.

**For every invariant that may exist, perception gets easier to understand and to implement on a machine.

In probability theory and statistics, covariance is a measure of how much two variables change together (variance is a special case of the covariance when the two variables are identical).

If two variables tend to vary together (that is, when one of them is above its expected value, then the other variable tends to be above its expected value too), then the covariance between the two variables will be positive. On the other hand, when one of them is above its expected value the other variable tends to be below its expected value, then the covariance between the two variables will be negative.