Sensation

1. Sensation

2. How would you define sensation? formal definition - immediate response in the brain caused by excitation of a sensory organ

3. What are the sense organs? Eyes, ears, tongue, skin, and nose

4. Based on what we know about the brain, do all the sense organs relay information to the same place? NO!

5. Localization of function The principal that the type of sensation experienced is related to the area of the brain activated.

6. How do data reduction systems work? One: Our sensory receptors are all biological transducers… …meaning they naturally convert energy from one system into another. Two: Each sense organ is most sensitive to a select type and range of energy.

7. As your sensory receptors transduce information, they also analyze the environment before they send the message to the brain. This separation of sensory information into important features is called sensory analysis.

8. Our sensory receptors are pre-tuned to specific stimulus patterns, called feature detectors. • The basic elements of a stimulus, such as lines, shapes, edges, colors, are called perceptual features. • Example: In a series of straight lines, a diagonal line would stand out to the eye.

9. Studies have shown that faces that are more symmetrical are found to be more attractive. Based on what we’ve just discussed, why would that be true?

10. Fun fact: Denzel Washington has one of the most symmetrical faces in Hollywood.

11. Back to the data reduction system… • Once our sensory receptors have selected and analyzed information, they must code it. • This is when they convert important features of the world into neural messages that can be understood by the brain. • This is called sensory coding.

12. These messages are then sent to certain areas of the brain, which respond according to their function. • So if someone punches you in the eye, your sensory receptors in the eye will respond somewhat to pressure, but they code the information visually, so you see bright spots and/or flashes of color. Remember!! • All of your sensory experiences actually take place in the brain.

13. Psychophysics • The study of the relationship between physical stimuli and the sensations they evoke in a human observer. • One of the basic questions psychophysics asks is: • “What is the absolute minimum amount of energy necessary for a sensation to occur?”

14. Absolute threshold • The minimum amount of physical energy needed to produce a sensation. • Vision – 3 photons of light • Equivalent to seeing a candle flame 30 miles away on a clear, dark night (remember this??)

15. Difference threshold • A change in stimulus intensity that is detectable to an observer. Just noticeable difference (JND) • Any noticeable difference in a stimulus.

16. Weber’s Law • The JND is a constant proportion of the original stimulus intensity. • Time for a demonstration!

17. Do absolute thresholds differ for different people? Of course! Type of stimulus, state of a person’s nervous system,costs of false “detections” and emotional states all effect the absolute threshold, even within the same individual

18. Unpleasant stimuli may raise the threshold for recognition. • Resistance to perceiving threatening or disturbing stimuli is called perceptual defense. • We process stimuli on more than one level. • Subliminal perception – perception of a stimulus below the threshold for conscious recognition