Task

Participants are provided with the following instruction: "You start a game in which your opponent has set a rule generating sequences of three numbers. Your goal is to find out this rule. For that purpose, you put forward sequences of numbers and your opponent tells you whether or not each sequence complies with the rule" Participants are presented with a valid sequence and with the hypothesis at hand (e.g., "Your opponent starts by telling you that the sequence 2-4-6 complies with the rule. You think that 'add 2' is the rule"). They are also presented with two candidate sequences, one confirming (e.g. "8-10-12") and one disconfirming (e.g., "3-6-9"). and they are asked to report whether or not they would put forward each one (Yes = 1 vs. No = 0).

Items (3)

Item 1

You start a game in which your opponent has set a rule generating sequences of three numbers. Your goal is to find out this rule. For that purpose, you put forward sequences of numbers and your opponent tells you whether or not each sequence complies with the rule. Your opponent starts by telling you that the sequence 2-4-6 complies with the rule. You think the rule is "add 2".

Indicate whether you would put forward each of the two sequences below to test this rule:

• 8-10-12 (confirming)

• 3-6-9 (disconfirming)

Screenshot (French version of the item):

Item 2

Same game but your opponent uses a different rule. She starts by telling you that the sequence 6-8-10 complies with the rule. You think the rule is "a sequence of even numbers".

Indicate whether you would put forward each of the two sequences below to test this rule:

• 3-5-7 (disconfirming)

• 2-4-6 (confirming)

Item 3

Same game but your opponent uses a different rule. She starts by telling you that the sequence 7-8-9 complies with the rule. You think the rule is "three numbers in ascending order".

Indicate whether you would put forward each of the two sequences below to test this rule:

• 1-2-3 (confirming)

• 6-4-2 (disconfirming)

Scoring

In each item, the confirmation bias score is the difference between the response to the confirming sequence (Yes = 1 vs. No = 0) and the response to the disconfirming sequence. The total score is calculated as the average of the three scores.