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

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.

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

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

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

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

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

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

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)