Marlene Likes to Get Email, and She Checks Her Electronic

Multiple Choice

Marlene likes to get email, and she checks her electronic mailbox frequently.Sometimes she gets 15 messages in a single day, and sometimes several days can go by with no new messages coming in.Based on what is known about schedules of reinforcement, you should conclude that Marlene's behavior of "checking her email" is being reinforced based on a:

A) fixed-ratio schedule
B) variable-ratio schedule
C) variable-interval schedule
D) fixed-interval schedule