Early research on classical conditioning was performed with dogs. In certain variations of this research, experimenters repeatedly presented dogs with meat powder just after ringing a bell. The dogs (who would naturally salivate after being exposed to meat powder) learned to associate the bell with the meat powder, and began to salivate as soon as they heard the bell. In this research, the dogs'

salivation was ____.

a. a conditioned response
b. an unconditioned response
c. a neutral stimulus
d. both an unconditioned response and a conditioned response

D