Sensation and Perception Exam 2 Study Guide
Sensation and Perception Exam 2 Study Guide EXP 4204
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This 12 page Study Guide was uploaded by Fiaza Ahmed on Monday February 22, 2016. The Study Guide belongs to EXP 4204 at Florida International University taught by Timothy Allen in Spring 2016. Since its upload, it has received 135 views. For similar materials see Sensation and Perception in Psychlogy at Florida International University.
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Date Created: 02/22/16
Exam 2 Study Guide: Phrenology: Study of the bumps on the head Different areas of the head are thought to correspond to different personality traits Phrenology is now synonymous with pseudoscience… and is often the insult a psychologists in one field hurdles at another field However wrong, phrenology contributed to the idea of localization as opposed to equipotentiality Organization of the brain: Maps – spatial distribution of information from sensory receptors such that adjacent points on the cortex correspond to adjacent areas of the retina Columns – vertical groupings of neurons perpendicular to the cortical surface processing similar sensory information Streams – sequentially-connected structures each contributing specific functions (like an assembly line) Modules – specialized regions of the brain processing specialized functions Distributed Representations – any one perceptual representation requires coding by several neurons in several regions, with a unique combination of activity fMRI: f. M. R. I.= Functional Magnetic Resonance Imaging B.O.L.D. = Blood Oxygen-Level Dependent No tracer needed Blood has ferrous molecules in it (iron) Changes in oxygenation changes signal properties More oxygenation in a given area is thought to correspond to more brain activity Slow (seconds) and large (1 – 2 mm3)—voxels (not pixels) Technique discovered in 1990 P.E.T. = Positron Emission Tomography • Positron emission – radiation from radioactive isotopes (proton to neutron) • Tomography – Mapping via slices • Must inject a radioactive tracer • Image blood flow • Changes in blood flow correspond to changing demands on a given brain region • Note the blood-flow-to-function interpretation is not a direct measure of brain activity • PET is very useful for measuring the spread of drugs, or neurotransmitter pools, etc. with different tracers (it is helpful in asking details about certain molecules) • Technique discovered in 1976… not thought to be dangerous (however it is not ideal to do too many) Visual Streams: “What” pathway “Where” pathway P-cells: (smaller ganglion cells, M-cells :(larger ganglion cells, layers 3-6 of LGN; process color layers 1-2 of LGN; process depth and texture) movement) Ventral (bottom) Dorsal (top) Temporal layer Parietal layer If damaged, people have If damaged, people don’t difficulty identifying faces know where things are in and objects. space Two-choice task: o Temporal lobe lesions: impaired object discrimination but not spatial discrimination o Parietal lobe lesions: impaired spatial discrimination but not object discrimination William Wundt Founded the first laboratory in scientific psychology Father of experimental psychology Structuralism (anti-thesis to Gestalt psychology): Percept is created by the sum of elements called sensations. *However we do have to consider organized perception Object Perception Perceptual Organization: How small parts are organized into wholes Multiple objects in the environment are grouped, to identify those objects in complex scenes. Two important processes in perceptual organization: Grouping: the process by which elements in a figure are brought together in common unit or object Segregation: the process of distinguishing two objects as being distinct or discrete Gestalt Psychology and Perceptual Organization: Gestalt theorists claimed that the brain is holistic with self- organizing tendencies We see greater than individual parts Conscious perception rests upon the building blocks of sensation A. Figure ground organization: The experience viewers have as to which part of an image is in front and which part of an image is in the background of a particular scene We divide the world into two elements: the figure that is the object of regard and the rest, which is ground or background. Things that are more memorable tend to be figure, while those that are not tend to be ground Figure more “thing-like” Figure is in front of the ground – Ground is a uniform material that extends behind the figure (good continuation) The figure has border ownership *Neurons in V1 are affected by figure/ground regions B. Gestalt Laws of Perceptual Grouping: Law of good continuation: the gestalt grouping law stating that edges that are smooth are more likely to be seen as continuous than edges that have abrupt or sharp angles Law of proximity: the gestalt grouping law stating that elements that are close together tend to be perceived as a unified group. Law of similarity: the gestalt grouping law stating that elements that are similar to one another tend to be perceived as a unified group. Law of symmetry: grouping law that states that elements that are symmetrical to each other tend to be perceived as a unified group Law of common fate: elements that are moving together tend to be perceived as a unified group Principle of common region: elements that are within the same region of space appear to be grouped together Principle of Uniform Connectedness: connected regions of visual properties are perceived as a single unit Principle of Synchrony: events that occur at the same time will be perceived as belonging together Perceptual Interpolation: Edge completion: the perception of a physically absent but inferred edge, allowing us to complete the perception of a partially hidden object Illusory contours: perceptual edges that exist because of edge completion but are not actually physically present. These illusory contours display edge completion. Recognition by Components: Bottom-up theory Geons: the basic units of objects, consisting of simple shapes such as cylinders and pyramids Recognition by components: a theory stating that object recognition occurs by representing each object as a combination of basic units (geons) that make up that object; we recognize that object by the relation of its geons Roughly 40 independent geons, and just about any object can be represented by the combination of these geons. Accounts for viewpoint invariance: objects are seen as the same regardless of the vantage point relative to a viewer. Principle of componential recovery: the ability to identify an object if we can identify its geons Limitations of this theory: letter recognition and face recognition *Alternative theory that accounts for viewpoint invariance is the Image description model: Many 2-D images of singular objects are stored in our perceptual memories. Theory accounts for objects that are more abstract Both of these theories tend to be true under certain conditions The Neuroanatomy and Physiology of Object perception: Representation of Shapes in Area V4 After info leaves V1 and heads toward extrastriate cortex along the ventral pathway, one of the important loci is V4 in the occipital lobe. V4 has been linked to color vision and also shapes perception V4 neurons have a preference for edges (complicated analysis) This area is involved in delineating shapes necessary for object recognition. Object Recognition in the Inferotemporal Area Inferotemporal (IT) area: the region in the temporal lobe that receives input from the ventral visual pathway; one of its functions is object identification Neurons in the IT have much larger receptive fields than those in V1 and V4 and seem to be devoted to detecting particular kinds of objects anywhere in the visual field rather than specific features in specific places. IT area seems to specialize in detecting specific objects from chairs to bears to faces rather than edges or contours. The Fusiform Face area and Face Recognition: The FFA: an area in the inferotemporal area of the temporal lobe that specializes in recognizing familiar faces It is located on the ventral surface of the temporal lobe Occipital face area: an area of the brain in the occipital lobe, associated with recognizing faces as distinct from other objects The Grill-Spector experiment Prosopagnosia: Prosopagnosia: face agnosia, resulting in deficit in perceiving faces. Damage to the FFA results in this From the Greek words “face” and “knowledge” Patients with this can recognize faces as faces but have difficulty remembering specific faces Evidence with developmental prosopagnosia supports the view that FFA is an area unique to face recognition Other IT Cortex Areas with Specific Object Recognition Functions The parahippocampal place area (PPA): An area within the IT cortex that appears to have the specific function of scene recognition Recognition of spatial landscapes Topographic agnosia: involves a deficit in recognizing spatial landscapes and is related to damage to the PPA. Another area in the IT cortex with a specific function is the extrastriate body area. This is activated when its cells view bodies or body parts but not faces. It may be that other areas of the IT cortex are also sensitive to particular stimuli. Grandmother Cells and Specific Coding in the IT cortex: Early on scientists debated where in the brain memories are stored Search for the “engram”: specific location of a specific memory Quiroga et al study (2005) able to find cells that were specific to individual people. Color Perception: Wavelengths of Light and Color: Visual spectrum: the band of wavelengths from 400 nm to 700 nm that people with normal vision can detect As frequency increases, wavelength decreases. 400 – 450nm – Violet 450-490nm – Blue 500-575nm – Green 575-590nm - Yellow 590-620nm – Orange 620-700nm – Red Heterochromatic light: white light consisting of many wavelengths Monochromatic light: consisting of one wavelength Spectral reflectance: the ratio of light reflected by an object at wavelength. Every object has particular characteristics that permit it to absorb some wavelengths of light and reflect other wavelengths of light. (Chromatic colors) Surfaces that reflect all light equally can be said to be achromatic, which means, without color. (White: surfaces that reflect the most light, Black: surfaces that absorb the most light and Gray: surfaces that reflect some but not all light) Hue, Saturation, Lightness and Brightness Perception of color refers to the three dimensions of color experience Hue: refers to the color quality of light and corresponds to the color names that we use, such as orange, purple, green, indigo, yellow, cyan, aquamarine, etc. Hue is the quality of color: a value that changes, but it does not make the value larger or smaller. Monochromatic colors (spectral colors): red, green, orange, yellow, and blue Nonspectral colors: combinations of more than one monochromatic colors, purple, brown, silver, gold, etc. Saturation: Refers to the purity of light. The more saturated the stimulus, the stronger the color experience, and the less saturated, the more it appears white or gray or black. Brightness: refers to the amount of light present. The more bright an object is, the easier it is to see and the more noticeable the colors are. Lightness: refers to the amount of light that gets reflected by a surface *Brightness usually applies to colors, whereas lightness usually refers to the white-gray-black continuum. Additive and Subtractive Color Mixing: Most of our sensations and perceptions do not mix the way colors do With a mix of three primary monochromatic colors we can recreate any other monochromatic light. Additive color mixing Subtractive color mixing When lights of different Creation of a new color by wavelengths are mixed the removal of wavelengths Mixing the lights of different from a light with a broad colors spectrum of wavelengths Occurs in TV Mixing paints or other Pointillism colored materials More common in the natural world The Retina and Color: S-Cone M-Cone L-Cone Maximum Maximum Maximum response to response to response to light at 420 nm light at 535 nm light at 565 nm Best at M stands for L stands for long perceiving blue medium Yellow side of Sensitive to Yellow-ish green red lower Sensitive to frequencies higher frequencies *There are many more M and L cones than there are S cones. S cones only make up 5% of the total number of cones *At least two cones are necessary for any color vision to work *M-cones and L-cones are very similar to each other *These cones have slightly different versions of opsin molecules Univariance, or why more than one receptor is necessary to see in color Principle of Univariance: any single cone system is colorblind, in the sense that different combinations of wavelength and intensity can result in the same response from the cone system. Color vision critically depends on the comparative inputs of the different cone systems This principle explains why we cannot see colors under nighttime lighting conditions. Disorders of Color Vision: Monochromat: completely color blind and has one functioning type of photoreceptor o Can match any wavelength in the spectra by adjusting the intensity of any wavelength o Color blind o 1in 100,000 o Poor Visual acuity because only rod vision Dichromat: somewhat color deficient. o Can match any wavelength in the spectra by adjusting any 2 wavelengths of light o Most common forms are sex-linked (X chromosome) Trichromat: Full normal color vision. o Can match any wavelength of light in the spectra by adjusting any 3 wavelengths The Trichromatic Theory of Color Vision Color vision is based on there being three elements in our visual system that respond differently to different wavelengths Occurs at the level of receptors Determined by color matching experiments The Opponent Theory of Color Perception Theory that color perception arises from three opponent mechanisms (red-green, blue-yellow, and black-white) Support for this theory o Non primary colors can look like combinations of two primary colors o In color sorting experiments, people tend to sort colors into four basic groups rather than three o Afterimages o Simultaneous color contrast: when our perception of one color is affected by a color that surrounds it (process is similar to lateral inhibiton) Cone opponent cells: Color sensitive cells that respond best when they are excited by the input from one cone in the center, but inhibited by the input from another cone type in the surround. (in LGN) Color Opponent cells: cells that are specific not to cones but to colors themselves (In V1) Double Opponent cells: cells that have a center, which is excited by one color and inhibited by the other. In the surround the pattern is reversed. Useful for detecting color edges. (In LGN) Depth and Size Perceptio n Monocular Depth Cues Monocular depth cues: information in the retinal image that gives us information about depth and distance but can be inferred from just a single retina Pictorial cues: o Occlusion: when an object partially hides or obstructs the view of a second object. Provides info about relative position, not absolute distance o Relative Height: objects closer to the horizon are seen as more distant. o Relative Size: the more distant the object, the smaller its image will be on the retina. o Familiar size: Comes into play when we judge distance on the basis of our existing knowledge of the sizes of objects. o Linear perspective: the pictorial depth cue that arises from the fact that parallel lines appear to converge as they recede into the distance. This serves as a cue to depth o Texture gradients: monocular depth cue the occurs because textures become finer as they recede in the distance. As the surface gets further away from us, this texture gets finer and appears smoother. o Atmospheric Perspective: pictorial depth cue that arises from the fact that objects in the distance appear blurred and tinged with blue. Our atmosphere scatters light, and it scatters blue light more than other wavelengths. Because not all light is traveling in a straight line to us, more distant objects should appear a bit fuzzy. o Shadows and shading: Enhance the perception of depth in images Motion Cues: o Motion Parallax: monocular depth cue arising from relative velocities of objects moving across the retinae of a moving person. Parallax refers to change in position. o Deletion: gradual occlusion of a moving object as it passes behind another object o Accretion: gradual reappearance of a moving object as it emerges from behind another object. o Optic flow: motion depth cue that refers to the relative motions of objects as the observer moves forward or back in a scene. Binocular Cues to Depth: Stereopsis-the sense of depth that we perceive from the visual system’s processing of the comparison of the two different images from each retina. o Binocular disparity: Arises because our two eyes are in different locations in our head and therefore have slightly different views of the world o Corresponding points on the retinas o Horoptor: The region in space where the two images from an object fall on corresponding locations on the two retinae. Disparate Images o Fall on non-corresponding points of the two eyes o Difference is called angle of disparity o Crossed disparity: images in front of the horoptor move to the temporal regions of the retinas (lateral) o Uncrossed disparity: images behind the horoptor move to the nasal regions of the retinas (medial)
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