Complexity

1. All scientific statements are ultimately analysable into two components: an a priori or structural aspect associated with the number of independent parameters to which the statement refers; and an a posteriori or metrical aspect, there being associated with each structural element a numerical quantity measuring the amount of credibility to be associated with the aspect of the statement. The amount of this structural information represents what is meant by the complexity of a statement about a system; it may alternatively be defined as the number of parameters needed to define it fully in space and time.

2. Environmental complexity refers to the quantity of stimuli configurations or concatenations of stimuli which an animal must discriminate among, and to which it selectively responds.