A pigeon is presented with a blue key and a red key in alternating order. in the presence of the blue key, it earns food on a vi 200-sec schedule. in the presence of the red key, it earns food on a vi 600-sec schedule. the vi 600-sec schedule is then changed to a vi 100-sec schedule. as a result, rate of response on the vi 200-sec schedule will ____, which is known as a(n) ____ contrast effect.
a. increase; negative
b. decrease; positive
c. increase; positive
d. decrease; negative
