Chapter 1. Wason Selection Task

1.1 Introduction

Do you reason correctly? Since this is a cognitive psychology class, you can probably predict that we will tell you that you don’t. In this experiment, we will examine a particular aspect of reasoning: hypothesis testing. You will be given a rule and asked to determine if it is true. You will be asked to check some cards to test the rule; that is, the cards allow you to collect evidence. The question is how you will select the evidence that will allow you to determine if the rule is correct.

1.2 Experiment Setup

1.3 Instructions

You will be given instructions and then a rule to test. To test the rule, you will be shown four cards. Each card will have a letter on one side and a number on the other side. Two of the cards have the letter-side face up, and two have the letter-side face down.

Read the instructions carefully for how to test the rule on each screen to properly complete the task.

1.4 Experiment

1.5 Results

1.6 Debriefing

Let us look at the basic Wason Selection Task:

To test a hypothesis, logic tells us you need to see if you can falsify the rule. You need to pick those cards that can tell you if the rule is wrong. So the correct answer is E and 7. The E (called p when writing this rule out for logic) is fairly obvious. If something other than a 4 is on the other side, you know the rule is wrong. The 7 (called not-q) is sometimes less obvious. However, if an E is on the other side you know the rule is wrong. Still many people pick the 4 (called q). Shouldn’t an E be on the other side? If, say, you find a K, what would that mean? Read the rule carefully: it says if an E is on one side, you have to have a 4 on the other side, but it does not say what has to be on the other side of a card with a 4. Many people do pick the E and 4 (the p & q choice) and not the correct response, which is the E and 7 (p and not-q). Wason, like so many psychologists, has discovered a little task that reveals one of the many heuristics (known more colloquially as rules of thumb) that we use in our decision making. This heuristic is call confirmation bias because we are seeking those choices that can lead to evidence that supports or confims the hypothesis, but not that stronger test for evidence that can falsify the hypothesis.

The question is why we make this error. The Griggs and Jackson Study (1990) suggests that instructions can influence how we perform on this task. The instructions are designed to change what you attend to. The different instructions tried to make you focus either more on evidence that confirms the hypothesis or on evidence that is not part of the hypothesis. Their results found a pattern: that directing attention in a different way changed how their participants responded. Perhaps in part, we make the confimation bias because we tend to focus on the elements that agree with whatever hypothesis we are thinking about.

References:

Cai, X., Li, F., Wang, Y., et al. (2011). Electrophysiological correlates of hypothesis evaluation: Revealed with a modified Wason's selection task. Brain Research, 1408, 17-26.

Griggs, R. A., & Jackson, S. L. (1990). Instructional effects on responses in Wason's selection task. British Journal of Psychology, 81(2), 197-204.

Wason, P. C. (1966). Reasoning. In B. Foss (ed.), New Horizons in Psychology. London: Penguin.

1.7 Quiz