Sensation and Perception Sensation vs. Perception What’s the Difference? Transduction: Converting incoming signals into neural activity Sensation: Sensory receptors/nervous system receive information from environment Perception: Organizing and interpreting sensory information to create a meaningful experience

Sensation and Perception Top-Down Processing: Recognition guided by higher level cognitive processes Connected to our Mental Representations “What do IEXPECT to perceive?” (Then you perceive that) Bottom-Up Processing: Recognition depends on information received by senses and then processed by the brain “I don’t know what to expect, so I guess I’ll just figure out after I sense it”

What’s this painting about. What do you EXPECT to perceive What’s this painting about? What do you EXPECT to perceive? Study it a minute before moving on…

How many of the 13 faces did you see How many of the 13 faces did you see? Go back to the last one and watch how fast your brain changes perception based on expectations

Sensation and Perception Top-Down Processing: Recognition guided by higher level cognitive processes Bottom-Up Processing: Recognition depends on information received by senses and then processed by the brain

More examples of Top-Down Processing Aoccdrnig to a 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 toatl mses and you can sitll raed it wouthit porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe. Top Down Processing

The next slide is an actual photograph, adjusted to pure black and white. Use “Bottom-Up” to see if you can figure it out…

Did you see it? Most don’t. You didn’t have any expectations set up for it! Click to the next slide and study it for a minute, then return to the original black and white. Your brain just adjusted to the new expectations!

Sensation and Perception Selective Attention You have VERY limited attention resources Cocktail Party Effect You can focus on your attention on one stimulus (at the expense of tuning out the rest

Sensation and Perception Selective Attention Inattentional Blindness Example 1 Example 2 Change Blindness Whodunnit (AFTER watching, make sure you click back to the opening scene) Gradual Change Door Experiment

Sensation and Perception Signal Detection Theory You haven’t read this yet, but the chart is helpful when you do  Was Stimulus Present? YES NO HIT FALSE ALARM (Type I Error) MISS (Type II Error) CORRECT REJECTION Was Stimulus Reported?

Sensation and Perception Signal Detection Theory Apply to: Soldier in the field at night hears a noise Doctor assesses a patient who thinks they have cancer Jury determining guilt for 1st Degree Murder Was Stimulus Present? YES NO HIT FALSE ALARM (Type I Error) MISS (Type II Error) CORRECT REJECTION Was Stimulus Reported?