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UNCW PSY 211 - Perception

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PSY 211 1st Edition Lecture 8 Outline of Current Lecture I. PerceptionII. General Perceptual PrinciplesIII. Current IssuesCurrent LecturePerceptionUnconscious Perceptions- Binocular Rivalry is when presented with different images, the two eyes can’t fuse the images, so they compete for access to awareness.- Backward Pattern Masking a method for erasing stimuli from conscious awareness andthus studying unconscious perceptionCheeseman and Merikle did an experiment using subjective and objective thresholds. They presented color-name primes for different durations (SOA’s), followed by multiple-choice test with 4 color-names. (chance = 25%)Three Conditions- Subjective: used SOA from pretest where subjects said they didn’t see anything but guessed correct 50% of the trials.- Objective: used SOA from pretest where subjects said they didn’t see anything but theirs guessing was a chance 25% of the trials.- Supraliminal: Long SOA, such that subjects said they saw the prime and choose the multiple-choice answer at 100%.An “Exclusion” Procedure for Studying Unconscious PerceptionOn each trail, a word is briefly flashed followed by presentation of a word stem. Then thesubjects were told to complete the stem with any 5-letter word except the one that was recently shown to them, and if the subject completed the stem with the flashed word, there was good evidence for unconscious perception. General Perceptual Principles- Perception is selective- role of attention; inattention blindnessThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Perception has organization and structure- Gestalt principles; visual constancies, depth- Perception involves hypothesis testing- bottom up and top down interactions - Perception is influenced by expectations- perceptual sets; USS Vincennes- Perception is active and constructive- eye movement; unconscious inferences. Gestalt PrinciplesFigure/ Ground Segregation: selecting one region of the stimulus array as the focus (figure) and the other as the background (this is often driven by attention or top-down processing).Figure/Ground Separation: distinguishing between figure and ground. Artists often play with what is figure and what is ground.Studying Global vs. Local Processing with Hierarchical (compund-letter) Stimuli- The subjects tasks is to name the letter at either the local (small letter) level or the global (large letter) level- The main finding is “Global Precedence” Effectso The reaction time to name letter on incongruent trials is Global < Localo Global interference (global levels slow naming of local letters) but no local interference (local level does not slow naming of global letter).Visual ConstanciesVisual Constancies are the accurate perception of an object as stable/ unchanging despitelarge variations in its retinal image.- Brightness- Color- Size- Shape- LocationDepth PerceptionIn depth perception the brain uses both monocular (one eye) and binocular (both eyes) cues to “create” depth.- Binocular Cueso Binocular Disparity (Stereopsis): the slightly different images on the left and the right retina due to separation of eyes.o Convergence: oculomotor cues based on convergence of eyes to focus on nearby objects.- Monocular Cueso Linear Perspective o Relative Sizeo Light and Shadowo Interpositiono Texture Gradientso Motion Parallaxo Accommodation: an oculomotor cue based on the degree to which the lens must be focused on objects at different distances.Bottom-Up Processing vs. Top-Down Processing- Association Areas: integration of information across modalities - Secondary Areas: combines basic features- Primary Areas: Basic FeaturesIn bottom-up processing the process starts in the primary areas and works its way up, and in top-down processing the processes starts in the association areas and works its way down.Bottom –Up- Data driven - Initiated by stimuli in the environment.Top-Down- Concept Driven- Initiated by context, knowledge, and expectationVisual Illusions are not just curiosities; they reveal the cues the brain uses to construct perceptual experiences.Current Issues in Perception- Synesthesia: activation of one sense or sensory feature based on stimulation from anothersense or featureo The most common form is color-graphemic synesthesia whereby letters or number are perceived in particular colors.- Multi-sensory integration: study how activation of one sense influences processing in other senseso Vision often dominated as in the McGurk effect (auditory bias), Ventriloquist effect (sound localization), and Rubber-hand illusion.- Direct Perception: the theory by J.J Gibson that important perceptual features (like motion and depth) are not constructed via mental representations but are instead picked-up directly from the environment.o Key ideas are optic flow (movement), texture gradients (depth), and affordances (actions enables by particular objects).- Embodied Perception: Idea that perceptual processes are shaped by non-perceptual factors including body state, emotion, motivation, etc.o Experimental examples include research showing that perception of hill slant and distance are influenced by current level of fatigue or


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