Fighting dysphagia with an unlikely weapon: Math (Part 1)

By George Barnes MS CCC-SLP

Co-author: Doreen Benson MS CCC-SLP

Thinking about thinking

Congratulations. You made it this far. The mathematical title didn’t scare you away. But it's ok if it makes you a little nervous. I mean, you haven't touched math since college, maybe even grade school. But there's a lot we can do with math to change the way we practice for the better. In this blog we are going to tell you why using statistics is important as an SLP. Next week we are going to tell you how to do it.

How our intuition has failed us

We are smart animals. Some argue the SMARTEST of the animals. Our brains are certainly wonderful things, but they often play tricks on us. This is because we like shortcuts. Shortcuts help us think fast. Thinking fast is important today, but 10,000 years ago it kept us ALIVE. Instead of analyzing a lion’s teeth, appetite, eating habits, and running speed; the only association we had to make was lion = RUN. Now, we are trying to backtrack because the quality of our thinking is often more valuable than its speed. Let’s talk about a few ways our ancient brains are failing us in the modern world.

Availability bias

The availability bias tells us that we tend to use what’s top of mind to make an overarching judgment on something. For example, we heard about a shark attack on the news and now we’re at the beach and it’s all we think about. This makes us think that a shark attack is way more likely than it is. We do this with plane crashes too. 

Causal fallacy

We like taking things that are associated and create a cause and effect that doesn’t actually exist. This is called a causal fallacy. For example, we associate kids who eat sugar with hyperactivity, but it’s actually the parties where they eat the sugar that makes them hyperactive. It’s also the reason why we think underdressing in cold weather makes you sick when only germs can do that (this one’s for you, mom). 

Base-rate fallacy

We also have a tendency to over-weigh anecdotal information and ignore the bigger picture. This is known as the base rate fallacy. For example, you are introduced to a shy lady with glasses who loves to read. Do you think this lady is more likely to be a librarian or a salesperson? The answer: Salesperson. If you thought ‘librarian’ that’s because you made the common mistake of over-weighing your personal experience or knowledge about librarians and completely ignoring the base rate: There are way more salespeople than librarians in the world.  

Why you should care

Enough about sharks, candy, and librarians, how does this relate to dysphagia? I’m so glad you asked. Let’s address how important each of these faulty lines of thinking is related to our clinical practice.

The availability bias- As soon as we see a patient we think of dysphagia first. As soon as we see a cough we think of aspiration. And as soon as we see an abnormal CXR we think of pneumonia. That’s because we were trained to think this way. We read case studies about abnormality, we study disease, and we focus on the impairment. It’s what’s top of mind. 

The causal fallacy- Why is it that we think that aspiration and aspiration alone causes pneumonia. Because we love this easy cause and effect formula: Something goes down the wrong pipe and causes an infection down there. But this misses the other factors that need to come into play in order to develop pneumonia.

Base-rate fallacy- We see a patient with pneumonia and immediately think it’s aspiration-related. This of course misses the base rate: The actual percentage of pneumonia cases that is aspiration related. Which is only about 10%.  Or how about the patient who has confirmed aspiration and we quickly fear that they are going to get pneumonia immediately. In fact, some of us discontinue an instrumental study the second a patient presents with trace aspiration because of this fear. But this ignores the base rate: The actual number of people who develop pneumonia after aspiration, which is tiny. 

Stay meta my friends

So maybe you’re letting your mind play tricks on you. Don’t fret, we all do it. Yet many don’t recognize it and most don’t even care about it. But you’re different. Feels good to be different, doesn’t it? And what should make you feel even better is the fact that there are fool-proof ways to protect you against it. It involves math. Statistics in particular. Next week we are going to tell you how it works.