Positive Test Strategies

A real danger for us, that I don’t know how to move beyond, is positive test strategy. It is the search for evidence that confirms what we want to believe or what we think is true. When we already have an intuition about something, we look for examples that support our intuition. Looking for examples that don’t support our thought, or situations where our idea seems to fall short, is uncomfortable, and not something we are very good at. Positive test strategies are a form of motivated rationality, where we find ways to justify what we want to believe, and find ways to align our beliefs with what happens to be best for us.

 

In Thinking Fast and Slow, Daniel Kahneman writes the following, “A deliberate search for confirming evidence, known as positive test strategy, is also how System 2 tests a hypothesis. Contrary  to the rules of philosophers of science, who advise testing hypothesis by trying to refute them, people (and scientists, quite often) seek data that are likely to be compatible with the beliefs they currently hold.” 

 

In science, the best way to conduct a study is to try to refute the null hypothesis, rather than to try to support the actual hypothesis. You take a condition about the world, try to make an informed guess about why you observe what you do, and then you formulate a null hypothesis before you begin any testing. Your null hypothesis says, actually nothing is happening here after all. So you might think that teenage drivers are more likely to get in car crashes at roundabouts than regular intersections, or that crickets are more likely to eat a certain type of grass. Your null hypothesis is that teenagers do not crash at roundabouts more than typical intersections and that crickets don’t display a preference for one type of grass over another.

 

In your experimental study, instead of seeking out confirmation to show that teenagers crash more at roundabouts or that crickets prefer a certain grass, you seek to prove that there is a difference in where teenagers crash and which grass crickets prefer. In other-words, you seek to disprove the null hypothesis (that there is no difference) rather than try to prove that something specific is happening. It is a subtle difference, but it is importance. Its also important to note that good science doesn’t seek to disprove the null hypothesis in a specific direction. Good science tries to avoid positive test strategies by showing that the nothing to see here hypothesis is wrong and that there is something to see, but it could be in any direction. If scientists do want to provide more evidence that it is in a given direction, they look for stronger evidence, and less chance of random sampling error.

 

In our minds however, we don’t often do this. We start to see a pattern of behavior or outcomes, and we start searching for explanations to what we see. We come up with a hypothesis, think of more things that would fit with our hypothesis, and we find ways to explain how things align with our hypothesis. In My Big Fat Greek Wedding, this is what the character Gus does when he tries to show that all words in the world are originally Greek.

 

Normally, we identify something that would be in our personal interest or would support our group identity in a way to help raise our social status. From there, we begin to adopt hypothesis about how the world should operate that support what is in our personal interest. We then look for ways to test our hypothesis that would support it, and we avoid situations where our hypothesis could be disproven. Finding things that support what we already want to believe is comforting and relatively easy compared to identifying a null hypothesis, testing it, and then examining the results without already having a pre-determined outcome that we want to see.

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