The ABCs of Sensation and Perception

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

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.

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?

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

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

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

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?

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

http://www.youtube.com/watch?v=oQd7rb0wkjY http://www.youtube.com/watch?v=Yt5xAO2MyVk

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”

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)