Sensory Interpretation: Weber's Law

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From the course by The University of Chicago

Understanding the Brain: The Neurobiology of Everyday Life

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The University of Chicago

Understanding the Brain: The Neurobiology of Everyday Life

624 ratings

Learn how the nervous system produces behavior, how we use our brain every day, and how neuroscience can explain the common problems afflicting people today. We will study functional human neuroanatomy and neuronal communication, and then use this information to understand how we perceive the outside world, move our bodies voluntarily, stay alive, and play well with others.

From the lesson

Perception and Vision

Perception is how the brain interprets incoming stimuli. Not all stimuli that can be sensed are perceivable, and sometimes those that can be perceived play tricks on us. The systematic ways that stimuli are interpreted (or misinterpreted) show how well the brain can understand our surroundings, sometimes with limited information. This module we will explore perception and vision.This module contains a lot of material, so be sure to start early so that you have time to finish!

Introduction to Perception4:01

Sensory Interpretation: Optical Illusions3:33

Sensory Interpretation: Auditory Illusions3:09

Sensory Interpretation: Weber's Law4:06

Stimulus Set7:07

The Road to Perception5:10

Name the Senses4:53

Meet the Instructors

Peggy Mason
Professor
Neurobiology

[MUSIC].

>> Let me introduce Marlon.

>> Hello.

>> Marlon Aguilar, who is one of the people who makes this possible.

And he is going to demonstrate another illusion,

or a perceptual feature, let's put it that way.

So Marlin.

>> Yes.

>> Do you feel these two?

>> Yes.

>> Okay, I'm taking them away.

>> Okay.

>> And I want you to tell me whether when I put them back

onto your hands, whether I've changed with our added to either one of them okay.

So get that in your memory.

>> Okay.

>> And you're closing your eyes, right?

Did I add weight to either one?

>> You added weight to the right side.

>> That is correct.

Okay we're going to play our little game again.

>> Lets remember what these two feel like.

Okay?

>> Okay.

>> All right and now I'm going to put them back.

Oh.

okay.

Now did either one of them change weight?

>> no.

>> Okay.

That's exactly right.

And in fact, one did change weight.

The one in his right hand, you can open your eyes now.

>> Okay.

>> Has a, has a dime on it.

Is he going to feel the dime when he's holding a book?

No, not going to happen.

So why not?

Thank you very much Marlon.

>> Thank you.

>> We are now going to explain this.

[SOUND] Why, why doesn't that happen?

Because we don't, we don't perceive.

The magnitude of a stimulus accurately.

We only perceive the magnitude of

a stimulus in relationship to the background.

So another way to put this is that the change in

perceptual magnitude is, is not proportional

to the change in stimulus intensity.

It's proportional to the change in stimulus intensity.

Divided by the background stimulus intensity.

So, in the first situation we were somewhere up here.

There's two books.

They are about the same, and I added another big chunk and, and so

Marlin could tell, that this, two books was, was more than one book.

In the second situation, we're up here and I

added a dime, and that didn't take us very far.

He can't tell that this, these are different.

Another situation and the situation which probably people, have a

lot of familiarity with in this is looking at a screen.

So this goes to the whole war between the backlit and, the non-backlit screens.

Well, there's not, one is not better than the other.

It just depends, on what your background stimulation is.

So what your background set of intensity.

So in a dark room there's very little background.

You don't need much change in intensity to see something.

So, backlit is fine.

In sun, in sunlight it's not going to cut it, you're not going to see it,

so you have this situation probably every day.

Computers work much, much better inside [LAUGH] then on a really bright sunny

day, and that's because of this lovely law which is called Weber's Law.

And it basically tells you

that you don't perceive the magnitude of a stimulus, accurately.

Rather we perceive it as a proportion of what

is the background stimulus in intensity that we're exposed to.

[MUSIC]

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