Sensation & Perception Intro

1. Sensation & Perception Intro Unit 4 – Chapters 5 & 6

2. Sensation & Perception How do we construct our representations of the external world?

3. Sensation vs. Perception Sensation: detecting physical energy from the environment and encoding it as neural signals **associated with bottom-up processing Perception: selecting, organizing, and interpreting our sensations as meaningful objects and events **associated with top-down processing

4. Sensation vs. Perception Examples: • Hearing – you “sense” the noises the vocal tract makes when a person speaks, you “perceive” the meaning of what those noises represent • Health Problem – you “sense” sudden pain in your heart, you “perceive” by recognizing you are suffering a heart attack

5. Bottom-Up Processing: analysis that begins with the sensory receptors and works up to the brain’s integration of sensory information Letter “A” is sensed as a black blotch decomposed into features by the brain and perceived as an “A” by our mind . “Thinking comes last” A  A

6. Top-Down Processing • guided by higher-level mental processes, such as experience, motivation, and expectations, we interpret what we see using context clues

7. Describe this picture (colors? How many men? Trees? Horses? Where is this?:

8. Title: “The Forest Has Eyes”Now what do you see?

9. Processing Bottom-Up Processing: Top-Down Processing: detecting lines, angles, and colors that form the horses, riders, and surroundings • considering the painting’s title, you noticed the apprehensive expressions, and attended to aspects that gave meaning

10. Absolute Threshold • Psychophysics: the study of how physical energy relates to our psychological experience • **What stimuli can we detect? At what intensity? How sensitive are we to changing situations? • Absolute Threshold: the minimum stimulation needed to detect a particular stimulus 50 percent of the time • candle flicker at 30 miles away on a clear night • Ticking watch in a quiet room

11. Difference Threshold • Difference Threshold: the minimum difference a person can detect between any two stimuli half the time • also called just noticeable difference (or jnd) • Example: slight flavor distance between two wines, child’s voice among other kids • Weber’s Law: difference thresholds differ by a constant percentage rather than amount • Example: Adding 1 pound to a 50 pound weight is enough to be a difference threshold; adding 1 pound to a 500 pound weight is not • Exact proportion varies by stimulus: weight must differ by 2%; light intensity by 8%

12. Signal Detection • Signal detection theory: predicts when we will detect weak stimuli amid background noise • Detection partly depends on experience, expectations, motivation, and fatigue level • Example: new parents detect faint noise from baby’s room despite loud TV blasting • Example: guard on duty – may hear faint noises due to alertness

13. Subliminal messages: stimuli below one’s absolute threshold • for a stimuli to be subliminal, we are not aware of it (it is unconsciously sensed)

14. Subliminal Messages FAQs • Do subliminal messages work? • To an extent: invisible words or images can prime your response to a later question • Can advertisers manipulate us with subliminal persuasion? • No. Subliminal messages have subtle, fleeting effects; they do not have powerful, enduring effects on behavior • People who KNOW they are receiving subliminal messages THINK it affects them, but it really doesn’t

15. Adaptation • Sensory Adaptation: diminished sensitivity as a consequence of constant stimulation • Examples: water’s cold at first but you get used to it • Moving your watch up an inch on your arm- bugs you at first, then no problem • Our eyes constantly flutter which prevents what we “see” from diminishing • sensory adaptation helps us focus on informative changes in the environment • As opposed to getting confused with too much stimuli

16. Senses – Where are we going…? • Vision • Hearing • Touch • Taste • Smell