The purpose of this activity is to explore whether individuals will engage in thinking forwards or thinking backwards as they solve a logic question.

Ask five individuals to answer the Lily Pad question:

A man has a pond and he wants to cover it completely with lily pads. He buys a variety that doubles in area each day and will cover his pond in 30 days.

Question: On what day will the pond be half covered?

There should only be 2 predicted responses (Day 15, Day 29). Day 15 is an incorrect response reasoning by heuristic (divide 30 days in half = 15). Day 29 is the correct response reasoning by thinking backwards (if Day 30 is full, then the dayBEFORE - Day 29 - has to behalf covered with lily pads). Representing thisvisually can really help. On Day 28, the pond is a fourth covered in lily pads, Day 27, the pond is an eighth covered....Day 1 - one lily pad.

Keep in mind that if a person responds with Day 15, they are thinking forwards through the problem (Day 1 to Day 30) and using a heuristic. This strategy leads to the wrong answer.

Ask the person to follow up an incorrect Day 15 answer with the question:

"Okay, on what day will the pond be completely covered?" Perhaps that will trigger the thinking of your participant. Hopefully, the participant will respond 'Day 16" AND then realize the wrong answer was given.

If a person responds with Day 29, this demonstrates thinking backwards through the problem (Day 30to Day 1) and have come up with the correct answer and used the right solution strategy.