PerceptionPsyc 100 1st EditionExam # 2 Study Guide Lectures: 10 - 16Lecture 10 (February 23)Sensation and Perception Stage 1:SensationThe processes of:- Converting the physical world into a mental representation (transduction)- And relaying that information to the brain (conduction)Stage 2:PerceptionThe processes of:  Selection, organization and interpretation Psychophysics The study of the relationship between the physical aspects of stimuli and our psychological experience of them.Absolute Threshold The smallest intensity of a stimulus that must be present for it to be detected.Difference Threshold The smallest level of added (or reduced) stimulation required to sense that a change in stimulus has occurred. The just noticeable difference distinguishes changed in loudness between sounds that are initially loud than it is for sounds that are initially soft, but the proportional increase remains the same.Weber’s Law A just noticeable difference is a constant proportion of the intensity of an intitial stimulus (rather than a constant amount)Sensory Adaptation An adjustment in sensory capacity after prolonged exposure to unchanging stimuli.SensationProcess of vision:1. Light enters cornea, cornea bends the light.2. Light then traverses the pupil, a dark hole in the center of the iris, the colored part of theeye.3. Light then passes through the lens, it lies directly behind the pupil and acts to bend rays of light so that they are properly focused on the rear of the eye.4. Light then reaches the retina where electromagnetic energy of light is converted to electrical impulses for transmission to the brain.5. The image reaches the retina upside down6. The brain then interprets the image in terms of its original position.Structure of the eye:Rods Thin, cylindrical receptor cells that are highly sensitive to light.Cones Cone shaped, light sensitive receptor cells that are responsible for sharp focus an color perception, particularly in bright light.Trichromatic Theory There are three kinds of cones in the retina, each of which responds primarily to a specific range of wavelengths. The perception of color is influences by the relative strength with which each of the three kinds of cones is activated.Color blindness When an individual cannot perceive green or red objects and instead they are perceived as yellow.Opponent Process Theory Receptors are linked in pairs, working in opposition to each other. This is the explanation for after imageAfter Image When activity in the retina continues even when you are no longer staring at the originalpicture.Process of hearing:1. Sound arrives at the outer ear in the form of wavelike vibrations and are funneled into the auditory canal.2. Vibrations are transferred to the middle ear.3. When sound enters the inner ear through the oval window, it moves into the cochlea, a coiled tube that looks something like a snail and is filled with fluid that vibrates in response to sound.4. Hair cells are bent by the vibrations entering the cochlea and the cells send a neural message to the brain.Structure of the ear:Outer ear The tube like passage that leads to the ear drum.Eardrum Part of the ear that vibrates when sound waves hit it.Middle ear A tiny chamber containing three bones: the hammer, the anvil, and the stirrup that transmit vibrations to the oval window. Middle ear acts as a type of amplifier. The hammer, anvil and stirrup act as a set of levers that transmit and increase the strength of vibrations.Oval Window A thin membrane leading to the inner eye.Inner ear Portion of the ear that changes the sound vibrations into a form in which they can be transmitted to the brain.PerceptionPerceptual Illusions Case where the rules that we use to interpret the world, which are usually true, are not true and lead us to misinterpretation.Examples of Visual Illusions:1. Vertical vs. Horizontal lines We tend to think that horizontal lines are shorter than the vertical lines2. Context effects An L in a handwritten note looks like a D in another word but is not read as such3. Experience effects the world Lines look different because of environment we grow up in (people who have grown up in a house with right angles vs people who have grown up in a round hut)Gestalt psychology Principle that identifies factors leading to a particular form of perceptual organization.Rule 1:Figure ground Perceive object as distinct from its surroundingRules of grouping:1. Proximity  Group nearby objects together2. Similarity  Group figures that are similar3. Continuity Perceive continuous patterns4. Connectedness Spots, lines and areas are seen as unit when connected (3&4) We opt for most simplistic interpretation (books calls simplicity)5. Closure  Fill in gapsPerceptual Constancy: We are able to perceive an object as unchanging even though the stimuli we receive from it change. Once we lock onto a particular interpretation of a stimulus, we tend to stick with thatperceptionTypes of constancy:1. Size Constancy  Position causes illusion that height or size has changed2. Shape Constancy  Orientation of object creates illusion that object has changed shapePerceptual set Expectations are a big determinant of how we perceive a scene.Depth PerceptionHow do we perceive depth?Two main sources of information:Binocular cues Rely on the fact that we have two eyes Each eye produces a slightly different image because the eyes are in different locations These cues are ones in which our brains imposes structure on the environment – Gestalt rulesLecture 11 (February 25)Monocular cues Can be perceived with one eye only These cues are ones in which brain makes use of info that exists in the environment.Examples of Binocular cues:Retinal Disparity  Images from the two eyes differ The larger the difference (disparity) between two images the retinas receive, the closer the object is to our eyes. Convergence  The closer something is, the larger the angle forms by the two eyes Two eyes move inward for near objectsExamples of Monocular cues:Interposition If A blocks B, then A must be closerRelative Size If 2 items are similar in appearance, then the one that “looks” smaller is farther awayClarity Clearer is closerTexture gradient Coarse is closer, smoother is farther awayRelative height Things higher in our field of vision are perceived as