In their attempts to discover the most basic form of learning, early
experimenters discovered two procedures, one called classical or
Pavlovian conditioning, the other called instrumental or operant con-
ditioning. Beginning in the 1930s traditional theorists, such as Skinner
( 1938), maintained that the two basic procedures represent two distinct
forms of learning. This view dominated research and theory throughout
the century even though hard evidence frequently contradicts the tradi-
tional theoretical distinction. The procedural distinction, however, re-
mains useful as a way to describe experiments in this field. Accordingly,
chapter 2 describes the experimental operations that define classical
conditioning and chapter 3 describes the experimental operations that
define instrumental conditioning. These descriptions should prepare
readers to make their own critical analysis of evidence and interpre-
tation that they encounter in this field. Later chapters consider the
relation between modern evidence and the traditional distinction.

This chapter describes the procedure known as classical or Pavlovian
conditioning. Experimental examples that used different species, dif-
ferent responses, and different stimuli illustrate the broad generality
of this procedure. Experimental examples from the 1930s to the 1990s
illustrate how well the basic findings have survived stringent tests of
time and replication.

-18-