>> NARRATOR What would you think if you watched a forensic
expert get on the witness stand and say 5 little words:
>> CLIP “The DNA is a match”?
>> NARRATOR The first thought that went through my mind?
Got ‘em.
DNA is the gold standard of forensic evidence; indisputable, right?
I mean, we’re talking about the stuff we send out to the lab to find out if we’re
.2% Italian (or in my neighbor’s case: 2% Neanderthal)!
But in 2011, neuroscientist Itiel Dror and biologist Greg Hampikian teamed up to show
that even DNA analysis can be vulnerable our blind spots.
Today, we’re talking about one of the strongest biases out there: confirmation bias.
Welcome to Outsmarting Human Minds.
Imagine this: you’re a forensic analyst on a criminal case.
>> CLIP “Fingerprint check on Panacek.”
>> NARRATOR The prosecutors tell you they have testimony
from one of the suspects...
>> CLIP “I will give you immunity if you testify.”
>> NARRATOR …and he’s revealed everyone else who was
involved in the crime.
The only snag?
Unless you can place at least one of those other people at the scene, the judge is probably
throwing this testimony out.
So: those are the stakes.
You have the DNA mixture from the crime (that means it includes more than one person’s DNA).
And you have DNA from the prime suspects.
So.
Is there a match?
These are details from a real criminal case.
And the real analysis team did find a match!
Suspect 3 was there.
“Got ‘em”, right?
Not exactly.
Years later, Dror and Hampikian sent the same DNA to 17 new experts: Did they see Suspect
3’s DNA in the mixture?
16 out of 17 experts said no.
This is the kind of situation where I think it’s fair to ask “What the heck happened?”
16 “nos” seems like the opposite of a “gotcha” moment.
But the original analysis team was qualified and competent. So how did they see something
so different?
The answer: confirmation bias.
Our tendency to search for or interpret new information in a way that supports what we
already believe.
You see, the one difference between the original analysts and the new ones was what they thought
was true.
The original team knew that there was incriminating testimony; they knew that without a DNA match,
the accused could go free.
The new analysts didn’t.
So they were looking at the data with untainted eyes.
And while DNA analyses are basically error-proof when it comes to single samples, when it comes to
DNA mixtures, there’s a lot more ambiguity.
Is that really an allele, or just a blip in the data?
Is there really enough information to make a conclusion, or is the sample too degraded
or complex to even try?
>> CLIP “The blood and DNA tests came back inconclusive.”
>> NARRATOR These are the kinds of decisions points where
bias can come in – even in honest people who are trying to be accurate!
Confirmation biases can affect all of us. And what makes them so hard to outsmart is
that we think we’re finding data that proves us right!
For instance: let’s say you just know that a colleague didn’t deserve that promotion.
You see him make a little mistake and aha!
Proof, right? ...even if it’s a slip you would have forgiven in anyone else.
What’s more, researchers at SUNY Stony Brook University found that when our opinions are
challenged – for instance, if you have to read both sides of a debate about gun control
or affirmative action – our original beliefs only get stronger after we hear the opposite
view
This is bizarre!
And it happens because we pick and choose.
We focus on the strengths of the arguments we like, and the flaws of the arguments we
don’t.
And that leaves us feeling even more firm in our convictions.
There are so many ways the confirmation bias can affect us: Maybe you want to invest in
a new business venture, and that’s making you downplay the risks.
Maybe you’re completely smitten by a new crush, so you miss seeing all the red flags.
All this tells us that if we want to outsmart our minds, we have to learn how to switch
from confirming an idea to proving it.
Here’s a few tips:
The desire to confirm can give us tunnel vision, but hindsight is 20/20.
So get used to conducting premortems.
That is: imagine that the unthinkable HAS happened.
>> CLIP “Breaking headlines…”
>> NARRATOR The company did go under.
>> CLIP “…filing for bankruptcy…”
>> NARRATOR The relationship did implode.
>> CLIP “…the two reportedly broke up…”
>> NARRATOR What killed it?
What signs did you miss?
Working backwards like this pushes you to find the clues that fell into your blind spot.
Another solution for the hypochondriacs among us: rethink what you’re typing into that
search bar.
“Do I have cancer?” is only going to confirm your worst fears, not give you the most likely
answers.
Instead, plug in your symptoms (or better yet) consult a professional.
Finally, reframe your goals.
Don’t make half-hearted pro-con lists that only tell you want to hear.
Whether it's a personal decision or an analysis for a Supreme Court case, make sure everyone
knows “success” means making the best decision, and not just the one you think is
right.
Outsmarting Human Minds is a project founded by Mahzarin Banaji, devoted to improving decision-making
using insights from psychological science.
The OHM Team includes Olivia Kang, Evan Younger, Kirsten Morehouse, and Mahzarin Banaji.
Research Assistants include Moshe Poliak and Megan Burns.
Music by Miracles of Modern Science.
Support for Outsmarting Human Minds comes from Harvard University, PwC, and Johnson
& Johnson.
For references and related materials, visit outsmartinghumanminds.org.