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  • NARRATOR: The name "Perkins" carved in stone.

  • Below a gothic tower a boy navigates with a cane.

  • A title: Visual Acuity Testing:

  • History of Preferential Looking and Early Testing

  • with D. Luisa Mayer, Ph.D.

  • - Preferential looking is something that a baby does

  • when they see something that's very interesting

  • next to something that isn't interesting.

  • So they prefer to look at something that's interesting.

  • I'll give you an example.

  • A three-month-old baby, if we show a three-month-old baby

  • a drawing of a face where all the features are regular--

  • the eyes are where they should be,

  • the nose is in the middle, the mouth is below--

  • and then you put next to that a drawing of the same features

  • of the face, but where everything's scrambled--

  • the eyes are over here, the nose is there,

  • the mouth is up here.

  • NARRATOR: We see the image of two faces side-by-side.

  • The image on the left is of a normal face.

  • And on the right the shapes depicting the eyes,

  • nose, hairline and eyebrows are randomly placed

  • within the same space.

  • - What's the baby going to look at?

  • The baby's going to look at that face that's regular

  • and not at the scrambled face.

  • We call that the baby's preference to look at a face.

  • So preferential looking has a really long history

  • as both, just natural observation of what babies do.

  • They naturally look at things.

  • Things they're interested in capture their attention

  • and they spend a lot of time looking at them.

  • And that observation started a whole field

  • of vision science,

  • studying the development of visual perception

  • and the development of sensory visual functions

  • in babies,

  • using modifications of this method now

  • that's called preferential looking.

  • The first person to do that formally was someone

  • named Robert Fantz,

  • who was an American developmental psychologist.

  • And he presented two stimuli like stripes and a bull's-eye

  • to babies and he looked at...

  • he measured which one they preferred

  • by having somebody just measure their looking time

  • to the stripes, to the bull's-eye.

  • He would change the position, measure their looking time,

  • say in a two-minute interval.

  • And cumulating their looking time

  • over that two-minute interval would tell you that the baby

  • preferred one or the other

  • if the time was sufficiently different.

  • NARRATOR: We see the two shapes as described,

  • on the left a bull's-eye of three concentric black rings

  • and on the right side,

  • six identical wide, black vertical stripes.

  • - And he did that starting with newborn babies,

  • babies shortly after birth.

  • To do that he had to create this funny-looking box

  • that he called a looking chamber,

  • but actually I call it the baby box.

  • And it's open on the bottom.

  • A baby is slid in lying on their back

  • underneath this box.

  • Someone is peeking over the top of the box,

  • looking through a little peephole.

  • And inside the box are either two objects or two images

  • that the baby's looking at.

  • So baby's down below looking up at these images

  • or these objects.

  • And the observer looking through that peephole

  • is measuring how much time the baby looks

  • at one or the other object.

  • NARRATOR: A black and white photograph

  • shows Fantz's apparatus.

  • An infant on its back gazes up at a balloon-like object

  • at the top of the box.

  • An observer stands to the left of the apparatus

  • on a small step stool and leans over the top of the box

  • to observe the baby through a small opening.

  • - When he did that with newborns, he found

  • that newborn babies actually have visual preferences.

  • They look at things, some things more than others.

  • And it turns out it's pretty complicated

  • and pretty interesting.

  • He also studied babies up to about six months of age,

  • sitting them upright in a little baby chair

  • and showing them also patterns and objects.

  • The bottom line of his findings with newborns

  • was that babies actually make visual discriminations.

  • They're not blind, they see differences between things.

  • It's fairly rudimentary, but nevertheless

  • they're making discriminations.

  • He considered that evidence for innate visual perception

  • in babies,

  • that babies are able to see forms right after birth.

  • They don't need experience.

  • Now, some would argue, well, they need some experience.

  • Well, yes, to refine their vision

  • certainly they need experience.

  • He also showed that babies had preferences

  • for certain things that changed over time.

  • They weren't always interested in looking at the bull's-eye

  • versus the stripes.

  • Later on they seemed to be more interested in stripes

  • than bull's-eyes.

  • But at all ages he found that babies preferred

  • to look at regular faces over scrambled faces.

  • So Fantz started doing these studies in the '50s.

  • And this type of work is really called

  • the study of visual perception in babies.

  • And it's been ongoing, there are all kinds

  • of modifications of this procedure used to study

  • complex visual perception and cognition in babies.

  • NARRATOR: Fade to black.

  • A graphic of the Perkins logo swoops across the screen,

  • revealing a chapter heading:

  • Visual Perception vs. Visual Sensory Function.

  • - I want to differentiate between what I mean

  • by sensory versus perceptual.

  • So sensory qualities of an object are things

  • that make up that object, that form,

  • such as the angles or the edges of a form,

  • the lines, the width of the lines that create that form.

  • Light/dark differences that define where that form is

  • in space.

  • Color differences and so forth.

  • So those are the components that go up to make a form,

  • and perception is seeing the form as a form,

  • seeing all those components put together,

  • and that creates an object that we can discriminate.

  • Now, the sensory visual functions that I'm talking about

  • that have been studied over many years

  • since shortly after Fantz's work are visual acuity,

  • detail vision, contrast sensitivity--

  • the ability to see different contrasts between objects--

  • color vision, temporal vision, motion sensitivity,

  • stereo, vernier acuity and a number of other

  • really basic visual functions.

  • The research started on these things really with babies

  • in the '60s, so shortly after mid-century.

  • Actually, there are a number of different modifications

  • of preferential looking that were used to test

  • visual sensory function.

  • I'm going to focus on one in particular

  • because it's what I know.

  • It's from the person I worked with,

  • it's where I did my graduate studies

  • and so you'll hear all about that.

  • But there were a number of other researchers

  • who used modifications of preferential looking

  • to study behavioral visual function in babies.

  • And I'm just going to name a couple of them

  • because they're prominent people,

  • they're people in our community

  • and they're good friends as well.

  • At MIT, Massachusetts Institute of Technology,

  • some of the first studies were done by Richard Held

  • and Jane Gwiazda on babies' vision.

  • And they were also very interested in clinical aspects--

  • so astigmatism, an abnormality of the eye

  • that causes visual acuity to be reduced.

  • And also Eileen Birch who was working in their lab

  • as a post-doc, and then now is at the Retina Foundation

  • in the Southwest and does a lot of really good research

  • on clinical aspects of visual function in babies.

  • And then there's a pair of people-- a couple--

  • from England who have been working

  • as long as everyone else:

  • Jen Atkinson and Oliver Braddock

  • from the United Kingdom.

  • These are just some people.

  • I can't name all of them.

  • There's a list of maybe 40 or 50 people