1. Sensation & Perception
A.P. Psychology
1/13/2010

2. Drill
Listen to this song, and differentiate between what is sensation and what is perception.
Feel free to describe your thoughts and feelings about the song. How does it make you feel? What is the temperament of the song? Etc.

3. Quick Review Gustav Fechner Ernst Weber
Threshold
Dividing point
Absolute Threshold
Minimum amount of stimulation that is detectable
Fechner’s Law
Magnitude of a sensory experience is proportional to the number of JND’s
Light example
Ernst Weber
Just Noticeable Difference (JND)
Smallest difference in amount of stimulation that can be detected
How is it different from absolute threshold?
Absolute threshold is the JND from no stimulus input
Weber’s Law
Size of JND is constant proportion of the size of initial stimulus
Weight’s example

4. Signal Detection Theory
Proposes that the detection of stimuli involves decision processes as well as sensory processes
Ex. You are charged with monitoring a radar screen, looking for signs of enemy aircraft. Your mission – detect signals that represent approaching airplanes as quickly and as accurately as possible

5. Signal Detection Theory
There are 4 possible outcomes:
1. Hits
Detecting signals when present
2. Misses
Failing to detect signals when present
3. False Alarms
Detecting signals when they are not present
4. Correct Rejections
Not detecting when they are absent

6. Signal Detection Theory
What influence do decision-making processes have on the outcome?
Criterion: how must you feel before you react (higher mental process rather than pure sensation) – depends upon your expectations & consequences for missing a signal
“Noise” Levels: your performance will also depend on this – the more background noise, the harder to detect weak signals

7. Signal Detection Theory
Another Example:
You are eagerly awaiting pizza delivery at a loud, raucous party
You want to detect a signal (the doorbell or knock)
But you have a lot of background noise (music, people talking)
And your criteria for “hearing” will change as the time for delivery draws near
Detectability:
Measured in terms of probability and depends on sensory processes & decision-making

8. Sensory Adaptation
A gradual decline in sensitivity to prolonged stimulation
Example: Garbage
The garbage has begun to smell – if you don’t remove the trash, but stay in the kitchen, the stench will begin to fade
In reality, the stimulus remains stable, but with continued exposure, your sensitivity to it decreases
This is an automatic function
It keeps us tuned into changes in our environment – especially those that may put us in danger

10. Homework Which of your senses is the most important to you? Why?
If you had to voluntarily give up one of your senses, which one would you choose? Why?
If you could have any “extra” sense, what would it be and why? (feel free to be creative)