Ignoring the negative

by Matt McCormick

“Isn’t it weird how celebrity deaths always come in threes?”

“I’m telling you, Asians are bad drivers.” 

“I know it’s not politically correct, but it's true, women just aren’t good at science.”

“I swear I have special dreams.  I dreamt the night before that my mom was going to have a car wreck and she did.”

Confirmation Bias is the mistake of selecting evidence that corroborates a pet hypothesis while ignoring or neglecting evidence that would disprove it. It’s the mother of all fallacies.  And the reason it persists is that it feels so right.  When you’re making the mistake, the conclusion you’re drawing has that shiny, aura of truthiness to it.

Humans are guilty of committing it in a wide range of circumstances. At the end of each semester, many students, including students in my (Prof. McCormick’s) Critical Thinking and Theory of Knowledge where we study confirmation bias extensively, blunder into it. They get a grade for the course that is surprisingly low and send an email to their professor asking to know what happened. As far as they knew, they were doing great in the course. They recall getting an A on an assignment, and doing pretty well on the midterm, and feeling pretty optimistic, so they can’t understand the low grade. Here’s a couple of real emails: 

Student Email 1: I just checked my grades for the Spring semester and was surprised to have earned an F. I completed the major assignments for the course and did well on the midterm (90%) and well on the final (85%). I know I didn't participate in the online forum as much as was required but I'm still confused about the grade. I took the class material seriously and did my best on every assignment assigned.

Professor McCormick (notice the grades highlighted in red here): Here are the grades I have for you. This syllabus gives the details about the grade structure. Check the math and check your returned assignments to make sure it's all right. If there's a clerical error, I'll fix it right away:

Question Sets: 0, 82, 0, 75, 0, 95 (6% each)

First paper: 78

Midterm: 90.5

Second paper: 85

Final: 85

Outside projects: 7/8

Google Group: 0/8

Attendance and participation: 0/8

So between the skipped question sets, the Group discussion and attendance, you gave up 34% of the grade. Even if you were making an A on everything else, that would put it down to a D.

Student 2: I'm emailing you in regards to my final grades. I was hoping you could provide a detailed summary of my grades for the semester so that I can understand how I received a D. I felt as though I did fairly well, particularly improving on the more major assignments, so I would just like to know how I still failed to pass. If you could email me a detailed summary of my grades, I would greatly appreciate it. Thank you.

Professor McCormick: Yeah, I was disappointed in your grades too. It seemed to me that you are capable of doing much better work, and being more responsible about turning stuff in. Here are the grades I have. Check the math with the grade structure on the syllabus and let me know if there is a clerical error asap: 

Question sets: 76, 0, 82, 0, 85, 56, 80 (6% each)

Evil paper 65

Midterm 68.5

Second paper: 75

Final exam: 85

Outside Projects: 6/8

Google Groups: 4/8

Attendance and participation: 6/8

So the skipped question sets took 12% off of your grade. You got a D on the first paper and didn't take the opportunity to rewrite it that I gave the class. You could have brought that up substantially. The Google Group points would have helped too since your overall score came out at 68%.

When we commit confirmation bias, we cherry pick the evidence that suits us. The student actively remembers the good grades, but missed assignments and low scores are forgotten.  Someone picks out the bad Asian driver, or the woman who does poorly at science, and then uses that to fortify their mistake. 

One more example:  over 50% of people think they’ve had prescient dreams or premonitions.  So suppose that you have 20 dreams a night, 365 days a year, for 10 years.  That’s 73,000 dreams. 

Which ones are notable and remembered?  The ones that seemed to have something to do with what happened the next day.  The dream you had that seemed to anticipate your mother’s car wreck leaps out in your memory as an extraordinary coincidence.  In China, there’s a saying, “No coincidence, no story.”  But more importantly, there are 72,998 dreams that weren’t special or notable. 

Clearly, having an accurate and objective grasp of the relevant evidence would serve us well. We don’t want to ignore evidence indicating something negative, disastrous, or dangerous because it doesn’t suit what we want to be true. Imagine if a doctor acquired a skewed view of the evidence concerning a potentially fatal disease this way. Suppose the Secretary of State ignored significant negative indicators in the behavior of an aggressive and hostile foreign country. Suppose a potential employer asked you how you did in your Critical Thinking course in college, and then she checked your transcripts against your distorted memory. Suppose you spend thousands of dollars over the years on losing lottery tickets because the occasional wins stick out in your mind so prominently, while the loses are forgotten.  Suppose you spend time praying to God frequently, hundreds or thousands of times in your life, and on the rare occasion when something vaguely resembling what you prayed for came true, you count that as an answered prayer, while ignoring the thousands of misses.  

Further Reading

• Confirmation bias: A ubiquitous phenomenon in many guises, by Ray Nickerson

Matt McCormick
Professor
Department of Philosophy
Sacramento State

(Note: A version of this piece was published on Matt's own blog Atheism: Proving the Negative on 6.4.13)