Perception Goals of the day: Selective attention Perceptual organization Depth & motion perception Perceptual adaptation Extra-sensory perception

Perception zThe process by which we select, organize and interpret our sensations zHow does it differ from sensation? ythe detection of energy from the physical environment and encoding it as neural signals in the brain

What is our most dominant perceptual sense? zWhen there is a conflict between information received by two or more senses, which sense tends to dominate? yVision zWhy? What about for dogs?

Selective attention zAt any moment, we focus our awareness on only a limited aspect of all that we are capable of experiencing. yCocktail party effect: selectively attending to only one voice among many

Figure-ground perception zPerception of an object as distinct from its surroundings

Perceptional organization zThe brain’s “rules” for constructing making distinctions among sensory data zGestalt psychologists yemphasized that the whole is different than the sum of the parts zJohn Locke ywhole equals sum of the parts

zImmanuel Kant yPerception depends on innate ways of organizing sensory experience zHow does perception relation to the question: What does it mean to be human? yWhat about technology that changes our perceptual abilities?

Depth perception zIs it innate or learned? yVisual cliff experiment zMonocular vs. binocular cues ytouch two pen tips together 2 inches in front of your nose with both eyes open, then with only one eye open zHow do we judge depth with two eyes, one eye?

Binocular cues zRetinal disparity: brain receives slightly different images from each eye (hold finger in front of nose--then close one eye and then the other--to see different retinal views) ysame with ears and sound location (hold one ear shut) zConvergence: neuromuscular cues from the greater inward turn of the eyes when they view a near object

Monocular cues zrelative size (if two are objectively the same, the one that casts smaller image is perceived as farther away) zinterposition (if one object partially blocks our view of the other, we see it as closer) zrelative clarity (because light from distant objects passes through more atmosphere, we perceive hazy objects as farther away) zrelative height (objects higher in our field of vision as farther away)

ztexture gradient (gradual change from a course distinct, texture to a fine, indistinct texture signals increasing distance) zrelative motion (as we move, objects closer to fixation point appear to move faster) zlinear perspective (parallel lines appear to converge with distance) zrelative brightness (nearby objects reflect more light to our eyes)

Perceptual constancy zAllows us to perceive an object as unchanging even though the stimuli we receive from it change zShape constancy: ywe perceive that familiar objects having a constant form, even when they cast different images on the retina zLightness constancy: ywe perceive an object as having constant lightness even while its illumination varies

Could you navigate in the world if everything you saw was upside down? zPerceptual adaptation yThe ability to adjust to an artificially displaced, or even inverted visual field x“inverted world” glasses experiment

Do we perceive what we want or expect to see? zPerceptual set ya mental disposition that influences what we perceive, readiness to perceive zContext ya given stimulus may trigger different perceptions based on the setting (context) in which it is perceived (setting) xYou will perceive your clothes differently depending on what others are wearing

Can there be perception without sensation? ESP zAt present, there is no scientific evidence of ESP and related phenomena (clairvoyance, telepathy, psychokinesis)