In a multiple-baseline study of the effects of reinforcement on social behaviors Dr. Stern studies three behaviors in one child:

talking to other children, frequency of playing with others, initiating contact with children her own age. What is wrong with these choices of target behavior?

a. reinforcing one behavior could easily influence the occurrence of the others
b. children are naturally sociable; such behavior cannot be reinforced
c. the playground is not a suitable site for research
d. it is not possible to operationally define these behaviors

A