Answers to Learning Practice

1. Jorge saves money because he shops at the end-of-the-month sales at Hecht’s.

Answer: Fixed interval. Jorge is negatively reinforced once a month (the last day of the month). He has learned to shop at the end of the month. (Neg. reinforcement because the store is taking away the high price for people who shop on the last day of the month.)

2. Chi Ling, a waitress, gets a tip from about 80% of her tables.

Answer: Variable ratio. Chi Ling needs to repeat her behaviors (waiting tables) frequently because her positive reinforcement is based on the number of tables she serves.

3. Betty keeps her expense account updated because her boss calls her for a meeting about once a week.

Answer: Variable interval. Betty is positively reinforced for having her information ready when the boss calls. Betty never knows when she will call, but Betty knows it’s about once a week.

4. Pierre’s homework is graded on every-other assignment.

Answer: Fixed ratio. Every two behaviors, Pierre gets a grade on his homework. He knows exactly which behaviors will be positively reinforced. (Assume that getting a grade is a good thing.)

5. Ann mails birthday cards that take about 3 days to reach her friends.

Answer: Variable interval. Ann knows her cards will reach her friends in an average of three days. She does not know the exact interval between mailing and hearing that her friend got the card. (Ann is positively reinforced by hearing that her friends get their cards.)

6. A charity receives a donation one time out of approximately every 10 requests it makes.

Answer: Variable ratio. The more requests the charity makes, the more donations it will receive. However, they never know which request will be the one to yield a donation. It’s at a proportion of 1 in 10. It is positive reinforcement.

7. Sam goes to Weight Watchers every Monday and gets weighed.

Answer: Fixed interval. Sam is negatively reinforced because he is losing weight. (Taking away pounds.) He gets this news every Friday—a set amount of time goes by between weighings.