Why teaching logic stands to reason
Drinking the right brand of cola will make you beautiful and popular. The people living in nearby neighbourhoods want to violate your rights and destroy your way of life. Blondes have more fun.
Well, maybe not. Messages such as these from misleading advertising, inflammatory news stories and biased political commentators have one thing in common: they attempt to further an agenda by discouraging their audience's use of logic and reasoning. By appealing to our egos, insecurities, fears and resentments, the media encourages us to buy certain products and services, vote for certain political candidates and watch certain television shows.
With their still-developing brains, children and teenagers can be particularly vulnerable to the influences of faulty logic.
As technology advances, the amount of information we are exposed to rises exponentially. Fewer than 30 years ago, students went to libraries and could spend hours scanning lengthy reference materials. Today, they can research any possible subject with just two thumbs and a smartphone. But although the accessibility of knowledge has increased dramatically, so has the availability of questionable (and downright false) information.
One of the fundamentals of scientific thinking is to use logic and evidence to develop theories, yet the overwhelming amount of often conflicting information that pours out of our televisions, laptops and smartphones makes this difficult to do. So how can we teach students to filter through the opinions, beliefs, accusations, conspiracy theories and falsehoods to find actual facts and evidence?
One of the first things I do each year, after explaining what logic and evidence are, is to give students a list of common examples of poor logic. Although many of these seem obvious, it is amazing how commonly they occur. But others are more difficult to detect at first glance. Some common examples include:
1 Correlation equals causation
Because two events occurred together, one must have caused the other.
2 Popular opinion
If many people believe something to be true, it must be true. This may include an endorsement from a celebrity who has no expertise on the subject in question.
3 Negative association
In order to discredit an idea or opinion I disagree with or dislike, I associate it with something negative or distasteful.
Students must explain what is wrong with the logic in each of these examples. The point is not for students to determine whether or not they agree with the statement, but to explain what is missing from or incorrect about the reasoning. Is any evidence given? Do the reasons presented have any actual connection to the statement being made?
After the students complete the activity, either alone or in pairs, we discuss the results as a class. Often there are at least two or three statements that no student is able to find fault with. Interestingly, these hard-to-spot fallacies are commonly used in advertisements and political rhetoric.
By the conclusion of the activity, students should have a better understanding of what constitutes good logic and how to use it in scientific investigations.
Seth Robey is a chemistry teacher in Chicago, US