00:01
Now let’s get into something called
psychophysics or Fechner’s law.
00:06
So Fechner, our good friend
Fechner, was actually
a student of Weber who
generated Weber’s law.
00:10
So this is sort of a furthering
or a variant of Weber’s law.
00:15
And it’s imparting some of the information,
but there’s a small twist to it.
00:19
So psychophysics quantitatively
investigates the relationship between
physical stimuli and the sensations
and perceptions that they affect.
00:27
So what it’s doing it’s actually
bringing some of the --
it’s bringing some of the
onus onto the subject.
00:33
So the person who’s
perceiving the stimulus.
00:35
So Fechner describes a logarithmic
relationship between perceived
intensity of a stimulus versus the
actual physical stimulus intensity.
00:42
So a lot of words, let’s break
that down into simple English.
00:44
So what we’re saying is as a subject,
what you’re perceiving in terms of change
is a little bit different than the
actual change that’s happening.
00:55
So,
when I say to you, “Can you
detect a change in brightness?”
For you arbitrary units, you can say if
this level of brightness is unit one,
how much until I see a change?
I’m going to call that unit two.
01:09
Now that difference
that we’re seeing
might not be exact
compared to the difference
that we’re physically
seeing, actually seeing.
01:16
So we’ve described actually
a logarithmic relationship
and that logarithm relationship
is the Fechner’s law.
01:23
And so we’ll kind of walkthrough
an example of that that helps us.
01:26
And that’s -- it’s
looking at, say, stars.
01:28
When you’re looking at a
star through a telescope
and you detect a certain level of brightness,
you might look at other stars around.
01:35
And I say to you, look and find me
another star that’s just a bit brighter,
like that’s the next closes
level of brightness.
01:45
And you’re going to look in
your telescope and you’re
going to say, “Oh, the
one here to the right.”
That one is just a
smidgen brighter.
01:54
Now that smidgen is a personal
unit that you’ve arbitrarily
assigned and that’s your
perception of brightness.
02:00
But that is actually, if you’re
looking at lumens of brightness,
the number that we’re going
to get is going to be a
logarithmic scale of what
we’re actually perceiving.
02:09
Okay. So that relationship is
really what you need to understand.
02:12
So in terms of the MCAT,
you’re not going to be put
through a Fechner’s law
actual mathematical question.
02:18
Most likely, they're going to
want you to know that that
relationship exists and that
it’s a logarithmic relationship.