Perception  How do we define it? How we recognize and interpret stimuli How we recognize and interpret stimuli Top down processing… Top down processing…  Remember, expectations and previous experiences play an influential role…

Selective Attention  Our senses can take in approximately 11,000 bits of information at a time BUT… We can only focus on one thing at a time…

Neisser’s Basketball Study  Inattentional Blindness Focusing on one stimulus prevents us from noticing others Focusing on one stimulus prevents us from noticing others The dancing gorilla (bear) The dancing gorilla (bear) Texting and driving! Texting and driving!

2 readers, one listener….  Cocktail Party Effect Can only understand one voice at a time Can only understand one voice at a time Can notice genderCan notice gender Can detect nameCan detect name

Just how much do we notice?  Change blindness We fail to notice changes in our environment when we are focusing on a specific issue. We fail to notice changes in our environment when we are focusing on a specific issue.

Pop Outs!  Striking distinctions grab our attention

Perceptual Illusions  Mislead us by playing on the way we organize and interpret our sensations (challenges our schema!)  Reveal how we normally organize our sensations (thus clues to mechanisms of perception) Visual Capture: Vision is our dominant sense (effects how we perceive our other senses) Visual Capture: Vision is our dominant sense (effects how we perceive our other senses) McGurk Effect (Youtube/edu)McGurk Effect (Youtube/edu)

Perceptual Organization  Visual Agnosia  See all parts of an image, but not the whole, (or meaning)

Gestalt (“form”)  “The whole is greater than the sum of its parts” We first group images as a whole, not as individual or isolated parts We first group images as a whole, not as individual or isolated parts Our natural tendancy is to see the whole image Our natural tendancy is to see the whole image

Gestalt: (  Figure and ground: We group objects into our foreground and background, focusing on one or the other…

Gestalt  Proximity: we group things by how close they are..

Gestalt  Similarity: We group things by their likeness

Gestalt  Continuity: We group flowing lines, shapes together (2 lines vs. 4…)

Gestalt  Closure

Depth Perception  Binocular Cues (interplay of two eyes) Retinal Disparity: each eye sees object from slightly different angle (brain computes difference in vision to judge depth) Retinal Disparity: each eye sees object from slightly different angle (brain computes difference in vision to judge depth) Convergence: eyes move together as item gets closer (brain detects convergence of eyes as measure of depth) Convergence: eyes move together as item gets closer (brain detects convergence of eyes as measure of depth)  The Finger Sausage!

Depth Perception  Monocular Cues Relative Size: the farther away, the smaller it appears.. Relative Size: the farther away, the smaller it appears..

Monocular Cues  Linear perspective: parallel lines appear to converge with distance…

Monocular Cues  Texture gradient The closer it is, the more texture we see… The closer it is, the more texture we see…

Monocular Cues  Interposition: Objects that obstruct others are in the foreground… Objects that obstruct others are in the foreground…

Monocular Cues  Relative Height: distant objects are seen as higher on the plane than those closer

Monocular Cues  Relative Clarity: The more clear, the closer it is…

Monocular Cues  Relative Motion: The faster it moves, the closer it is…

Monocular Cues  Light and Shadow: cast perceptual cues of depth

Motion Perception  Phi Phenomenon: The illusion of movement by flashing lights or objects…  Troxler Effect (finger movement-peripheral)  With loss of sight- motion is usually first to be restored

Perceptual Constancy  Perceiving an object as unchanging despite a change in stimulus  Key factors: Experience, Expectation (Rules of perception)  Size Constancy: As stimulus changes, we literally see changing size, but we know size has not changed due to experience and context of objects surroundings As stimulus changes, we literally see changing size, but we know size has not changed due to experience and context of objects surroundings

Size Constancy

Shape Constancy  We know shape is constant even though our angle and thus vision of object changes

Lightness (Color) Constancy  We see objects as having consistent color, even as changing conditions alter the wavelength reflecting off the object.

Perceptual Set  “To believe it is to see it”  Our expectations, previous experiences strongly influence our perception

Context Effect  The context in which a stimulus appears affects how we perceive it… “…eel is on the wagon.” “…eel is on the wagon.” “…eel is on the orange.” “…eel is on the orange.”

Sensory Deprivation / Restored Vision  Adults with vision for first time (cataract surgery) Have Sense of colors, detect figure from ground Have Sense of colors, detect figure from ground No depth perception, no perceptual constancy (cortical cells not developed) No depth perception, no perceptual constancy (cortical cells not developed) *Much of perception is learned during critical period in early development *Much of perception is learned during critical period in early development

Perceptual Adaptation  Our brain can perceptually adapt to changes in our environment  Inverted goggles!!

Perceptual Constancy pages  Shape constancy  Size constancy  Light constancy

 Sensory Deprivation and Restored Vision  Perceptual Adaptation  Perceptual Set  Context Effects