Sensation and Perception

https://www.youtube.com/watch?v=oSQJP40PcGI

Sensation vs. Perception The process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment Perception The process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events

Bottom-up Processing Analysis of the stimulus begins with the sense receptors and works up to the level of the brain and mind. (simple to high) Letter “A” is really a black blotch broken down into features by the brain that we perceive as an “A.”

THE CHT Top-Down Processing Information processing guided by higher-level mental processes as we construct perceptions, drawing on our experience and expectations. (analytical) THE CHT

Example of Top-Down Processing Aoccdrnig to rscheearch at Cmabrigde Uinervtisy, it deosn't mttaer in waht oredr the ltteers in a wrod are, the olny iprmoetnt tihng is taht the frist and lsat ltteer be at the rghit pclae. The rset can be a total mses and you can sitll raed it wouthit a porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe.

Making sense of Complexity Top-down and Bottom-Up both work together to help us sort out complex issues

Selective Attention Focusing conscious awareness on a particular stimulus to the exclusion of others The ability to focus on one stimulus at a time Allows a person to function in a world filled with many stimuli

PSA fMRI scans reveal that brain activity in areas vital to driving decreases by 37% when a driver is attending to a conversation

https://www.youtube.com/watch?v=VkrrVozZR2c

Inattentional Blindness Failing to see visible objects when our attention is directed elsewhere

Change Blindness Failing to notice changes in the environment

Transduction Transforming of stimulus energies into neural impulses our brain can interpret

Absolute Threshold The minimum amount of a stimulation needed to detect a particular stimulus Amount of a stimulus that a person can detect 50% of the time

Detection Absolute Threshold Intensity No No No Yes Yes Detected Observer’s Response Detected Tell when you (the observer) detect the light.

Absolute Thresholds for Humans Vision: Candle flame seen at 30 miles on a clear, dark night Hearing: Tick of a watch under quiet conditions at 20 feet Touch: A bee's wing falling on your cheek from 1 centimeter above Smell: 1 Drop of perfume diffused into a three-room apartment Taste: 1 Teaspoon of sugar in 2 gallons of water

Difference Threshold Minimum difference between two stimuli required for detection 50% of the time, also called just noticeable difference (JND) Difference Threshold No No Yes Observer’s Response Tell when you (observer) detect a difference in the light.

Weber’s Law The size of the JND is proportional to the intensity of the stimulus If the stimulus intensity is high, the JND will be large (or it will take a bigger increase to be noticed) If the stimulus intensity is low, the JND will be smaller (or it will take less of an increase to be noticed)

Subliminal Threshold When stimuli are below one’s absolute threshold for our conscious awareness In other words…for most people these items are not detected

“Subliminal” messages in advertisements

More subtle subliminal messages…….

Signal Detection Theory Assumes there is no absolute threshold Depends on an individuals experience, expectations, motivation, and alertness

Sensory Thresholds Sensory adaptation Diminished sensitivity as a consequence of constant stimulation An adjustment of the senses to the level of stimulation they are receiving

What do these letters spell? F O L K

What do these letters spell? C R O A K

What do these letters spell? K

What do we call the white of an egg?

Influences on Perception

Perceptual Set

Perceptual Set A mental predisposition to perceive something one way and not another Example of top-down processing Influence of the “power of suggestion” (subliminal perception) Guided by schemas: concepts or mental frameworks that organize and interpret information (develop from experience)

Context Effect Different stimulus may trigger radically different perceptions

The “little guy” shown here is actually 6’9 who would tower over most of us The other guy is the world’s tallest basketball player at that time, 7’9