Evaluating Scientific Sounding Claims

Two stories on the radio this week got me thinking about the ways that we use science and how scientific discoveries are communicated to us. The first had to do with research on the toxoplasma parasite carried by cats (toxoplasma gondii). This parasite can cause toxoplasmosis in humans, an illness that can cause death in children and adults and birth defects in the fetus. (If you have a cat litter box, wash your hands after cleaning it!) The argument went something like, toxoplasm is carried by cats. Cats began to be domesticated by humans and were very common at about the same time that rates of schizophrenia increased rapidly around the turn of the century, therefore there might be a relationship between keeping cats as pets and schizophrenia. The full episode of Radiolab, which aired the segment, can be found here.

Another story examined the role of microbes in human life. Everything from the beneficial bacteria in our stomach to more esoteric microbes that can affect our behavior. The point seemed to be that microbes could be the master controller of human behavior. The full NPR story is here.

Both stories are admittedly intriguing and the scientists interviewed are not crackpots. So how do we really evaluate the science we hear and apply it sensibly in our lives?

One thing to keep foremost in our minds is that a relationship between two events does not tell us anything about the causality that may or may not link them. Because schizophrenia increased when we started keeping cats as pets does not establish a causal relationship between cats and schizophrenia. In fairness, the relationship between certain mental illnesses and toxoplasma has been reported elsewhere, I’m exaggerating somewhat to make a point.

The relationships between these issues is complex. There is more interdependence, or what statisticians call covariance, than direct causal relationships among the variables. It is more interesting to talk about the possibility of grand relationships and science fiction than to tackle the nuances of the relationships. Who wants to read a dry science article when we can talk about protozoa taking over our minds.

So the point is to take science reporting at face value. Dig deeper if a topic interests you and treat grandiose claims as what they are, bad science.

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