Can you have causation without correlation? (Surprisingly, yes)

March 14, 2022

Here are five ways you can have correlation without causation: 1. Averaging: increasing A sometimes causes increasing B, but other times, it causes B to decrease. The two balance out. Since correlation measures the average relationship, the correlation is zero. For example, if you drive up a symmetrical hill and then down the other side, there’s no correlation between how many times the wheels have revolved on the hill and the car’s height above sea level, even though the revolving of the...

It can be shockingly hard just to understand three variables

April 19, 2021

In science (and when developing hypotheses more generally), it is very common to come across situations where a variable of interest (let’s call this the dependent variable, “Y”) is strongly correlated with at least two other variables (let’s call them “A” and “B”). Here are some examples: If you’re a psychology researcher investigating possible causes of depression (Y), you may have trouble disentangling the effects of poor sleep quality (A) and anxiety (B), both of which tend to be corre...

What’s the link between depression and anxiety?

January 10, 2021

This image is from my colleague Amanda Metskas’ post on the Clearer Thinking blog, “Understanding the two most common mental health problems in the world:” https://www.clearerthinking.org/post/understanding-the-two-most-common-mental-health-problems-in-the-world

If you study depression and anxiety (in the U.S.), you find that they are correlated to a shockingly high degree (e.g., in one of my studies, when I correlated PHQ-9 depression scale scores with GAD-7 anxiety scale scores, I found that r = 0.82 ). Additionally, many studies have found that SSRIs (and other medications) help people with both depression and anxiety, as do certain therapeutic modalities such as Cognitive Behavioral Therapy, suggesting further linkage. Fin...

The Relationship Between Personality and Life Satisfaction

November 16, 2018

What's the relationship between personality and life satisfaction? We took a stab at figuring it out! We conducted a study of 999 people in the United States; recruited through our study platform at Positly.com. We looked for a correlation between 18 different personality traits (each trait being assessed with two questions) and life satisfaction. We examined the association each trait had with scores on the Satisfaction With Life Scale (a 5 question scale by Diener, Emmons, Larsen, Griffi...

Correlation Coefficient as a Gateway to Skepticism

June 14, 2017

The correlation coefficient as a gateway to radical skepticism:Suppose you calculate that two variables are moderately correlated. For instance, you find that self-reported happiness has a correlation r=0.32 with self-reported willpower, as I found in one of my studies. What are the possible explanations for (or causes of) this? A Causes B - Increasing A is a cause of increasing B but not the reverse. [e.g., more happiness causes more willpower] (2) B Causes A - Increasing B is a cause ...

How Journalism Distorts Reality

April 7, 2012

Journalism provides us with important information about what's going on in the world. But when you consider the incentives that journalists have, combine that with their usual lack of scientific training, and add in the constraints of the medium in which they work, serious distortions of reality can result. Many journalists produce excellent work. But others leave you less informed after reading their articles than before you began. What causes journalistic distortion? 1. Equal time to eac...