1. The ABCs of Sensation and Perception

2. Review of Sensation and Perception
Hearing a song on the radio
Sound waves enter your ear
Tasting broccoli
Chemical substances enter receptors in tongue
Seeing your friend’s new sweater
Light waves through your eye
Feeling happy because you remember the time you were with your friend and you heard that song
Spitting it back out because you hate broccoli
Thinking how much you like the sweater

3. Sense Receptors
Specialized cells located in the sense organs that convert physical energy in the environment or the body to electrical energy that can be transmitted as nerve impulses to the brain.

4. Absolute Threshold
The smallest amount of stimulus needed in order to detect that the stimulus is present.
If it is below AT, then we cannot perceive stimulus
If it is at or above AT, then we can perceive stimulus
Must be reliably detectable at least 50% of the time
Does absolute threshold vary by person?

5. Examples of Absolute Threshold
Sense
Threshold
Sight
A candle flame at 30 miles on a clear, dark night
Hearing
The tick of a watch 20 feet away in a quiet room
Smell
One drop of perfume diffused throughout a three-room apartment
Taste
1 teaspoon of sugar in 2 gallons of water
Touch
A bee’s wing falling on the cheek from 1 centimeter above

6. Difference Threshold (Just Noticeable Difference)
The smallest difference between two stimuli that is detectable 50% of the time
Depends of the intensity or size of the first stimulus
The larger or more intense the first stimulus is, the greater the change must be before you detect a signal

7. Signal Detection Theory
When are you more likely to hear sounds, or see things?
Seeks to explain why people detect signals in some situations but miss them in others
The detection of a stimulus depends on both the intensity of the stimulus and the physical and psychological state of the individual

8. Sensory Adaptation
Tendency of sensory receptor cells to become less responsive to a stimulus that is unchanging
Spares us from having to respond to unimportant information
Rarely adapt to:
Extreme stimuli
Visual stimuli
What would happen if our senses did not adapted to unchanging stimuli?

9. Sensory Deprivation
The absence of normal levels of sensory stimulation.
Can lead to people feeling edgy, confused, disoriented.
Can also be relaxing.

11. Selective Attention
Focusing your attention on selected aspects of the environment and blocking out others
Often happens during intense focusing, or when people have “sensory overload”
“Cocktail party effect”

12. Putting it all together
Absolute Threshold, Difference Threshold, Signal Detection Theory, Sensory Adaptation, and Selective Attention all attempt to explain how, when, and why we sense and perceive stimulus (things)