This document discusses key concepts related to sensory perception thresholds. It defines the difference threshold as the smallest detectable change between two stimuli. The absolute threshold is the lowest level at which a single stimulus can be detected. Sensory adaptation is described as decreased sensitivity to a stimulus with repeated exposure. Weber's Law states that for a difference to be perceived, the stimuli must differ by a constant proportion rather than a constant amount. Examples are provided to illustrate these concepts related to detecting changes in stimuli.

2. Slide adapted from Slideshare

3. Slide adapted from Slideshare

5. Concepts to Master
Some of the terms in this lesson are
difficult to apply to real life
examples. Let's “talk” through these
concepts by 1st discussing the
thresholds. They are the point
above which a stimulus is perceived
or below which it is not perceived. It
determines when we first become
aware of a stimulus.

6. Difference Threshold or Just Noticeable Difference
The difference threshold is the
smallest change in stimulus that we
can detect. Another way to say it, it
is the amount of change necessary to
recognize that a change has
occurred between two stimuli. The
key here is the difference between
2 stimuli.
For example: an artist might detect
the difference between two very
similar colors.
Image public domain

7. Absolute Threshold
The absolute threshold is the smallest amount of stimulus that
can be detected. Or you can explain it this way, it is the lowest
level that a person can sense a stimulus (sensation).
For example, the softest sound or the slightest touch.
❖ When a stimulus has more energy than the absolute
threshold, we can detect its presence.
❖ When a stimulus has less energy than the absolute
threshold, we can not detect its presence.
**Everyone's absolute threshold is different. It is based on how
well you can hear, see, smell, etc...

8. Sensory Adaptation & Weber’s Law
Sensory adaptation - repeated of constant
stimulation decreases the number of sensory
messages sent to the brain, which causes
decreased sensation. Or, it is a reduced
sensitivity to a stimulation after repeated
exposure to that stimulus.
For example - when you first jump into a pool
the water seems cold, but the longer you stay
in you no longer feel the cold.
Weber's Law is related to the difference
threshold/just noticeable difference, but states that to
really perceive a difference, the stimuli must differ by
a constant proportion, not a constant amount.
For example, if you hold a pebble in your hand and
then add a pebble of similar size you will probably
notice an increase in weight. If you hold a very
heavy rock in your hand and add a pebble you will
probably not notice an increase in weight.