Perception The process of organizing and interpreting information, enabling us to recognize meaningful objects and events. Auditory Illusions If the sounds do not work click here for link. Absolute Threshold • The smallest amount of a stimuli we can detect about half of the time. Subliminal Messages Do you hear "Now he uses marijuana.“? Do you hear “Ah, see me. I'm not too young”? • Stimuli below our absolute threshold. • Backmasking • 25th frame • Do Subliminal Messages work? • Probably a placebo effect Do you hear Pass the Do you backwards. Hear gunhear"Play now. It kills the words sung.“? love, the love is cold”? (Just Notable Difference) Difference Threshold The smallest amount of change needed to detect in a stimulus before we detect a change. Weber’s Law • Computes the Just Noticeable Difference. • The change needed is proportional to the original intensity of the stimulus. • The more intense the stimulus the more change is needed to notice the difference. • 8% for vision. Perceptual Ideas Signal Detection theory • Absolute thresholds are not really absolute. • Things like motivation or physical state can effect what we sense. • False Positives • False Negatives My wife could sleep through a war, but if one of our sons even whimpers, she is up!!! Top-Down Processing • We perceive by filling the gaps in what we sense. • I _ant ch_co_ate ic_ cr_am. • Based on our experiences and schemas. • If you see many old men in glasses, you are more apt to process a picture of an old man (even when you may be in error). Bottom-Up Processing • Also called feature analysis. • We use the features on the object itself to build a perception. • Takes longer that top-down but is more accurate. Click to see an example of bottom –up processing. Figure Ground Relationship Our first perceptual decision is what is the image is the figure and what is the background. Gestalt Psychology • Gestalt psychologists focused on how we GROUP objects together. • We innately look at things in groups and not as isolated elements. • Proximity (group objects that are close together as being part of same group) • Similarity (objects similar in appearance are perceived as being part of same group) • Continuity (objects that form a continuous form are perceived as same group) • Closure (like top-down processing…we fill gaps in if we can recognize it) Constancy • Objects change in our eyes constantly as we or they move….but we are able to maintain content perception • Shape Constancy • Size Constancy • Brightness Constancy Perceived Motion • Stroboscopic effect (flip book effect) • Phi phenomenon • Autokinetic Effect (if people stare at a white spotlight in a dark room, it appears to move.) Depth Cues • Eleanor Gibson and her Visual Cliff Experiment. • If you are old enough to crawl, you are old enough to see depth perception. • We see depth by using two cues that researchers have put in two categories: • Monocular Cues • Binocular Cues Monocular Cues • You really only need one eye to use these (used in art classes to show depth). • Linear Perspective • Interposition • Relative size • Texture gradient • Shadowing Binocular Cues • We need both of our eyes to use these cues. • Retinal Disparity (as an object comes closer to us, the differences in images between our eyes becomes greater. • Convergence (as an object comes closer our eyes have to come together to keep focused on the object).