let’s take a look at Signal Detection
Theory and we’re going to look at
what are some of the different
things that impact signal detection.
So what we’re talking about when
we’re saying signal detection is
detecting the presence of a stimulus
if there are things going on.
So we’ll walk through a lot f examples but
first, let’s highlight these four factors.
The first is alertness.
How alert are you in terms of
trying to identify the stimulus?
So are you completely focused and alert
saying, “I’m looking for a certain stimulus”?
Are you expecting that?
Is there some level of expectation?
Or are you completely unaware of whether
or not the stimulus is going to arrive?
Is there a motivation?
Are you motivated to try
and detect that stimulus?
And experience. Have you ever
experience this stimulus before?
If there was a previous
experience, then you might be
tuned to and be behaviorally
aware of what to expect.
look at the analogy of, let’s say, if you’re
looking at your child, you’re a mother
and your child is now missing,
and you’re at a -- you’re at a carnival
or a festival and your child has ran off.
you are looking for your child and you are
completely in tuned to hearing their voice.
Okay. So little Timmy has run
off and you’re the mother
and you are listening to, you’re completely
alerted to, little Timmy’s voice.
You know that little Timmy likes
to hide underneath large trees.
So there are some
expectations as well.
So you’re going to start looking at that
expectation and experience together.
You’re looking at trees, places
that he has done this before.
And then there’s motivation.
Obviously, as a mother, you’re
highly motivated to find your child.
So collectively, all these things will
elevate your ability to detect the stimulus.
Okay? So that’s a kind of stimulation
detection theory as a whole.
this can be an active
versus a passive process
and we’re going to walk through
some of those scenarios.
based on --
based on the four factors
that we just mentioned;
detection and influencing factors,
there are four possible outcomes that you
can have when looking at signal detection.
Now when we’re saying active,
we’re referring to you
allocating some resources
towards that signal detection
versus passive when you’re
sort of just sitting there
and the stimulus is
being presented to you,
and you’re not actively
really doing much other than
just detecting it once
it’s presented to you.
you have a matrix here
that we’ve created
and here are options, is that the
stimulus is present or it’s not there.
Okay. So it’s in front of you
or it’s not in front of you.
And you’re either going to detect it
or you’re not going to detect it.
if the stimulus is present
and the stimulus is not detected,
we say that that’s a missed.
You did not detect the stimulus
even though it was there.
If it was missing and
you didn’t detect it,
you correctly rejected it.
if the stimulus is present
and you’ve detected
it, that’s a hit.
If the stimulus was missing
and you detected it,
that’s a false alarm.
So what we’re going to do is if you take
this matrix and have it cut in half,
if you look at the scenarios where there
was a missed and a correct rejection,
we would say that that
individual is quite conservative
because they’re not actively
trying to detect the stimulus.
Versus where it says stimulus detected
and then we have a hit and false alarm,
that person is much more aggressive
in trying to find a stimulus,
which is why you have a greater
success of getting a hit
which you also have the chance
of getting that false alarm.
The reason we’ve created this matrix is
to give you some understanding as to
when you’re looking
for a stimulus,
you’re trying to detect it,
you can be quite active
or aggressive or you
can be a little more
passive and conservative,
and that will impact
your success rate.
Now we’re talking about detecting all
of this stimulus and responding to it.
But once you do
that, what happens?
Well most of the time, you’re
going to respond to it.
Now eventually when you
respond to enough stimuli,
you start to adapt.
And what we’re saying here is that
you’re going to change over time
the way you respond
to certain stimulus.
So it’s defined as the change
over time in the responsiveness
of the sensory system
to a constant stimulus.
And that’s the key
term here is constant.
So what I’m saying to you is if you are
constantly being inundated with the stimulus,
over time you will
adapt to that.
I had mentioned this earlier
in another lecture and
that we’re saying that our
brain is actually designed
to tune out what we call
And that’s a kind of a misnomer because
it’s not that it’s not important,
it’s just that right now, biologically speaking,
it’s really not that relevant to you.
And your body likes to detect change
and not constant information.
So you want to see how is this
different than things normally appear.
If it’s different, then
I’m going to really focus
in on and determine what
that difference is.
So think of the situation
of, you know, putting
on a watch, and you wear
that watch every day.
Is it really relevant for
your sensory receptors to
feel and know that you’re
wearing a watch all time
or the clothes that you wear?
Your body doesn’t really need to
know that information all the time.
It is tuned that out and it is saying,
“I understand I have clothes on
hopefully, and that I don’t need
to know that all the time.”
Think about the last time you had
a nice big bowl of spicy soup.
You’re eating this soup and
the first, first few bites,
your tongue is on fire
and you’re sweating.
What happens by the
end of the bowl?
You actually start
to get used to it.
You get adapted to it and you’re
kind of like, “This isn’t so bad.”
That is your sensory receptors getting
adapted to that level of spiciness.
Now one group of receptors that actually
do not adapt are the nociceptors
which are aligned
to detect pain.
And it’s one of the reasons why
it doesn’t matter how many times
you get slapped in the face
or you get kicked in the leg,
you’re going to feel that
and you’re going to feel
it just as bad over time.