Because of this coherent variation we can have knowledge of the variation of aspects that are not being perceived. For example, when we view a rotating die, we know what the back side is doing and can predict its reappearance. In the case of the conceptual tracking of substances we are interested in aspects that are approximately invariant over successive encounters with the substance. These are the aspects that cohere in the concept and about which it provides information. Therefore, after learning, variations in certain aspects of a stimulus will lead to neural activity that mimics or primes the response to variation in other aspects that have been correlated with them in the past.
Invariants become a means for generating expectations and filling in missing information.
The primacy of the concrete is also apparent in the context sensitivity of features. The reduction of their meaning to simple, low-dimensional predicates is secondary, and in part a consequence of descriptionist presuppositions and values. This observation even applies to such apparently abstract predicates as color terms, and part of our difficulty in understanding the use of such terms is a consequence of descriptionist assumptions. Multiplexing in single cells of the alert monkey's visual cortex during brightness discrimination. What computers can't do .