2. Absolute Threshold
The weakest amount of a stimulus that a person
can detect.
Sight Seeing a candle flame 30 miles away on a clear night
Hearing Hearing a watch ticking 20 feet away
Touch
Feeling a bee’s wing falling a distance of 1cm onto
your cheek
Smell Smelling one drop of perfume in a three room house
Taste
Tasting one teaspoon of sugar dissolved in two
gallons of water
3. Difference Threshold
The smallest amount of change in a physical stimulus that
a person can detect. This is also called the “just
noticeable difference.”
If someone turns
the music up slowly,
at what point do you
notice it has become
louder?
If you hold a
handful of sand, and
someone adds one
grain at a time to the
pile, when do you
notice it has become
heavier?
If your best
friend trims a half
inch off of their hair,
will you notice the
difference?
4. Absolute Threshold Difference Threshold
The weakest amount of a stimulus
you can detect.
The smallest amount of change in
a stimulus you can detect.
Review:
I can see a
candle flame
30 miles away!
(But not 31
miles away!)
I can see a difference
between these two
color hues:
But not between these
two:
5. Signal Detection Theory
It is impossible to process every simultaneous
stimulus equally in our brains. Instead, we focus our
attention on certain things while at the same time
attempting to ignore the flood of information
entering our senses. When we do this, our brains
decide what is important to sense and what should
be in the background. This concept is referred to as
signal detection because we detect what we want to
focus on, and ignore everything else.
6. Sensory Adaptation
Sensory adaptation is our
ability become to less
sensitive to an unchanging
stimulus. Ever wonder why
we notice certain smells or
sounds right away and then
after a while they fade into
the background? If a
stimulus has become
redundant or remains
unchanged for an extended
period of time, we begin to
ignore it.
Without sensory adaptation, you
would feel the constant pressure
of clothes on your body - you
would be bombarded with
sensory information.
7. Sensory Adaptation
Clock ticking in the room? Funny
smell in the room? Eventually you
will stop noticing them. Eating spicy
food? Eventually it will taste less
spicy. Step into a hot bath? At first
it might feel too hot, but eventually
it feels cooler. Walk into a dark
room? At first it will be too dark to
see, but then it becomes lighter.
These are examples of sensory
adaptation.
8. Signal Detection Theory Sensory Adaptation
When multiple stimuli are
present, this is our ability to
recognize some signals, while
ignoring others.
Our ability to become less
sensitive to an unchanging
stimulus over time.
Review:
I detected
the ring of my
cell phone,
even though
there are
other
auditory
stimuli in the
room!
That construction next
door is so LOUD and
distracting!
Fifteen Minutes Later…
Oh! I forgot there was
construction going on outside.
I started to ignore it.
