Now let’s get into something called
psychophysics or Fechner’s law.
So Fechner, our good friend
Fechner, was actually
a student of Weber who
generated Weber’s law.
So this is sort of a furthering
or a deviant of Weber’s law.
And it’s imparting some of the information,
but there’s a small twist to it.
So psychophysics quantitatively
investigates the relationship between
physical stimuli and the sensations
and perceptions that they affect.
So what it’s doing it’s actually
bringing some of the --
it’s bringing some of the
onus onto the subject.
So the person who’s
perceiving the stimulus.
So Fechner describes a logarithmic
relationship between perceived
intensity of a stimulus versus the
actual physical stimulus intensity.
So a lot of words, let’s break
that down into simple English.
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.
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.
Now that difference
that we’re seeing
might not be exact
compared to the difference
that we’re physically
seeing, actually seeing.
So we’ve described actually
a logarithmic relationship
and that logarithm relationship
is the Fechner’s law.
And so we’ll kind of walkthrough
an example of that that helps us.
And that’s -- it’s
looking at, say, stars.
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.
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.
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
Now that smidgen is a personal
unit that you’ve arbitrarily
assigned and that’s your
perception of brightness.
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.
Okay. So that relationship is
really what you need to understand.
So in terms of the MCAT,
you’re not going to be put
through a Fechner’s law
actual mathematical question.
Most likely, they're going to
want you to know that that
relationship exists and that
it’s a logarithmic relationship.