LUKE GROSKIN: How quickly do you judge someone by their face?
Don't deny it.
We all do it.
The question is, how fast.
Care to find out?
JOHN FREEMAN: I'm John Freeman.
And I study how the brain extracts information
from faces.
LUKE GROSKIN: See?
You're doing it right now.
JOHN FREEMAN: Faces are special in the sense
that they provide really significant information
about other people within 100 milliseconds.
LUKE GROSKIN: That's faster than the blink of an eye.
JOHN FREEMAN: Information from the retina about a face
travels back to the early visual cortex,
to the back of the brain.
And then it's sent forward through the rest of the brain.
LUKE GROSKIN: To be analyzed and scrutinized
by different and dedicated regions of your brain.
That you can look at a face for less than a second
and assess gender, race, age, emotional state
is an evolutionary feat.
JOHN FREEMAN: Now, it's also interesting to consider
why we may have mechanisms in place to judge personality
traits.
LUKE GROSKIN: Just as quickly.
To understand exactly how we make these snap character
assessments, using an fMRI machine is, well, a no-brainer.
JOHN FREEMAN: When neurons in a brain region
start to activate more, oxygen and glucose
have to rapidly flow in.
And using fMRI, they'll highlight
with colors what brain regions are
involved in a particular kind of task
or correlated with some kind of perception.
LUKE GROSKIN: For example, if you perceive a face,
your fusiform cortex will light up.
JOHN FREEMAN: It's thought to be an evolutionarily
dedicated mechanism for faces.
LUKE GROSKIN: Now, if you think the owner of that face
may help you or harm you, another part
of your brain known as the amygdala will react as well.
JOHN FREEMAN: It processes fearful expressions
of other people.
It's involved in motivating rapid responses to threaten
stimuli, for example.
LUKE GROSKIN: It's also an extremely fast judge
of trustworthiness.
JOHN FREEMAN: We'll put subjects into the scanner
and then present faces that vary in trustworthiness
for 33 milliseconds.
LUKE GROSKIN: Here's what 33 milliseconds of a face
looks like.
Did you catch that?
No worries if you didn't.
The test subjects didn't either.
And they didn't even know it was coming.
JOHN FREEMAN: So within those 33 milliseconds
we presented a face, it hit early visual cortex
and started feeding forward and was able to, in this case,
modulate amygdala responses.
LUKE GROSKIN: But the part of the brain that
helps you to actually consciously
see that face, the fusiform cortex, wasn't activated.
JOHN FREEMAN: So it suggests that the brain can process
the trustworthiness of a face without even
perceptual awareness, so without even being aware that a face is
being presented.
LUKE GROSKIN: The exact neurological mechanisms
that allow us to judge a face before we can consciously see
it have yet to be discovered.
But Dr. Freeman is inclined to believe
that our rapidly responsive amygdala could just
be tinting our view.
JOHN FREEMAN: Even on an emotionally neutral face,
we see a subtle resemblance to an emotion
and then run with that hypothesis.
So one idea is that a lot of these personality judgments
that we make quite spontaneously are bleeding over
from emotion perception.
LUKE GROSKIN: And trustworthiness
isn't the only type of snap judgment
that can be altered by tiny facial cues.
It happens with gender perception too.
Using software that tracks the computer mouse
movements of people asked to judge a face,
Dr. Freeman could determine how we perceive that face.
JOHN FREEMAN: So for example, if we take a standard male face
and make it very slightly feminine using computer
morphing, what we'll see is that even though they ultimately
select male response, they will be partially,
simultaneously attracted to select
female response on the opposite side of the screen.
LUKE GROSKIN: This swerve towards the female-gendered
response represents the subjects' preconceptions
of what a male face looks like.
And while it only lasts a few milliseconds,
it can have real world consequences.
JOHN FREEMAN: What we did was we presented male and female
politicians' faces.
So these are real politicians' faces.
And what we showed was that that kind
of slight swinging towards a male response before hitting
female was significantly predictive
of her electoral failure, particularly
in conservative states.
LUKE GROSKIN: Evidence that any politician's appearance
can affect their electability shouldn't surprise you.
That a split second look at a female politician's face
might influence your vote should give you pause.
JOHN FREEMAN: Seeing how subtle the cues are
that we use to infer so many important, meaningful
characteristics about another person
and how powerful these judgments are, I think,
is something that's really startling.
LUKE GROSKIN: Knowing how powerful a first impression can
be just might make you think twice before you judge a face.
For Science Friday, I'm Luke Groskin.