Which of B.F. Skinner's schedules of reinforcement is the most difficult to extinguish? (Hint: Gambling utilizes this reinforcement schedule).

A psychologist conditions your dog to salivate to a bell. Later, when your dog is home, someone rings the doorbell and the dog drools all over the floor. What process has occurred?

a) extinction b) acquisition c) generalization d) discrimination

All of the following are indications of a reactive attachment disorder EXCEPT

a) feeding difficulties. b) increased independence of the child. c) unresponsiveness to social overtures. d) a general failure to thrive.