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Exposing people...ah... to um images that are beneath conscious awareness...um
is called subliminal priming. It's a standard technique that we use...ah both in
social psychology and in cognitive psychology...um
Now after the subliminal priming procedure, we asked the participants to
perform...um...an unrelated, a supposedly unrelated...um
object detection task. And for this task participants were
presented with a series of objects that were severely degraded. Okay.
These objects appeared on the screen one at a time.
And...um. Each was slowly brought into focus in a series of four
And...um. Each was slowly brought into focus in a series of forty-one steps.
Okay. So here is an example of this, where there is an object that's completely degraded
And I'm just showing key points along the continuum here
so by the end, you can clearly see what the object is.
And the participant's goal, this time, is to indicate with a button push the moment
at which they can recognize what that object was. Okay.
Some of these objects were crime relevant like guns and knives
and others were..ah...crime irrelevant like staplers and cameras.
Okay. So the particpants were either exposed to the black male faces
or the white male faces, or no faces at all. And then all of them did this
object detection task on both the crime relevant and the crime irrelevant objects.
And we hypothesize that the participants who were exposed to the black male faces initially
would need less time to...ah...detect the crime relevant objects.
So here, um are the results.
Here along the vertical access we have the frame number...um
in the continuum at which they could recognize what that object was.
That goes from frame one where it is degraded, to frame forty-one where it's completely
clear. And the first thing we'll notice...um is that for the crime irrelevant
objects, it makes no difference whether they're exposed to the black faces or the
white faces or no faces before hand. They're recognizing those crime
irrelevant objects at about the same point...um in the continuum.
But you get a really different pattern, when you look at what they do for the crime relevant
objects. So you can see here, that simple exposure to the black
faces beforehand, drastically reduces the perceptual threshold
at which they could recognize what those objects were. Okay.
So they need a lot less information to say, "Oh, that's a gun"
or "That's a knife". And when we expose them to the white faces beforehand,
you get the opposite effect. They need a lot more information. They need more clarity
before they're able to say to you. "Oh, that's a gun" or "That's a knife".
Okay. So exposure to the black faces facilitated the detection
of these crime object. Whereas, exposure to the white faces inhibited
the detection of those very same objects.
Now...uh... the next set of studies I want to present have to do with the issue of racial
profiling. Um...so..um the idea here is that...uh when people
think black, they think crime. And so the
first study, I just presented demonstrates this. But we...my colleagues and I wanted
to argue...um that the association works in the opposite way as well.
So when people think about crime, they think about black people.Okay.
Thinking about crime, draws attention to black Americans.
Under these conditions, ...uh black people are...um...placed under surveillance.
So I'm going to give you an example of this. This is another study my colleagues and I conducted with white male undergraduates.
Um... this time, half of the particpants were sublimally
primed...um... uh with crime objects on the computer screen. And here it is in
slow motion. Um...and...um next the participants were
asked to complete a dot probe task. Okay. And so for the dot
probe task. They were shown on a computer screen a
black face and a white face, simultaneously. This time, they were shown the faces
long enough to be detected. Those faces came on the screen and then they disappeared.
And a dot appeared where one of the faces used to be. Okay.
And the particpant's goal was to simply locate that dot on the
computer screen as quickly as possible. Tell us whether that dot was to the left or the right
um...of the computer screen. Okay. Um... And we hypothesized that when
the dot was in the location of the black face. Um...
the participants who had been exposed to these crime objects beforehand would be
faster at finding that dot than those who had not been exposed to those images.
So the idea is that, once we get people to think about crime. They'll begin to look at
the black face. And we use the speed at which they can find this dot as a proxy
for visual attention. The faster they are at finding that dot, the more likely it is
for visual attention. The faster they are at finding that dot, the more likely
it is that they're showing an attentional bias in that direction the whole time.
Okay. So here are the results...uh..here for this study.
We have along the vertical axis, the mean reaction time to locate that dot
on the computer screen. And the first thing we are going to do is to look at...ah...what
happens when they're not primed with any crime images at all. And you can see here,
um... that they're faster to locate the dot...um when that dot is placed near the white face
Than when it's placed near the black face. Okay. So they're faster to locate that dot because
they're looking at the white face. So when there is no manipulation at all,
there is an in-group bias going on, where white faces are attracting white
study participants. Now...uh...when the..uh when the students are
primed to think of crime, ...um we get just the opposite effect.
Okay. They look at the black face. Um...so as expected
exposing people to the crime relevant objects placed the black male
faces under surveillance.
Now, we repeated this study with police officers. Um...
so the question here is, when police officers are on the lookout for
criminal activity, when they're thinking about violent crime,
Will this lead them to focus on black faces?
Um...so this study is quite similar to the study I just showed you, but
in this case we primed half of the police officers with words associated with violent crime
rather than images. So we exposed these officers to words like apprehend, arrest,
capture, shoot. And you can see here that the pattern...um of results is identitcal
to what we see with the students.
Okay. When the police officers are...um...are encouraged to
think of arresting and shooting and capturing. They're drawn to the black face.
Now at the very end of the study,
we took police officers through a suprise face identification task.
We presented them with a black line-up and a white line-up, and we simply asked them
to pick out the face that they were shown earlier in the study.
Now here's the black line-up. Um...one of these faces we actually used in the real
study with the officers. And it's also the face that I showed
you in an earlier slide, when I first... um introduced the study.
How many people know, which is the target face?
Is it...How many people think it's 4? Okay.
So the correct answer is number four. So that's pretty good.
Better than a lot of the police officers actually. [Giggle][Laughter]...Um
oh...well they...the police officers actually were able to do this... ah task
at above chance level. So they could identify the target at above chance levels.
But when they made a mistake on this task, the errors that they made
were systematic. So what happened...um was. Oh! Let me explain...um
We chose two of these faces to put in this line-up because they were rated by a seperate
group of study particpants, as more stereotypically black than the target. So those were faces
2 and 3. And then the other two faces were placed in the line-up because
they were rated as less stereotypically black than the target. So those were faces were 1 and 5.
And what happened is, when the...uh..the officers made an error on this task. And they were primed to think of
crime. They thought they saw face number 3 or they thought they saw face number 2.
Okay. So these results could have implications for eyewitness
testimony. Black people who appear most stereotypically black may be
the most vulnerable to false identifications in real line-ups.
Now results like these could also have implications for sentencing decisions. Ah...
in the next study I'm going to present, my colleagues and I were interested in