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Text Lecture 2 Schwartz The problem for the designer is to ensure all visual queries can be effectively and rapidly served. Semantically meaningful graphic objects need to have the right amount of salience. Visual queries should be supported with the most visually distinct objects. The PVC has been mapped by Hubel & Wiesel, (1981) The PVC has a number of interlocking layered sub-regions, each of which respond to either color, shape, texture, motion, or depth. The PVC sub-regions are– V1, V2, V3 V4, and V5 http://en.wikipedia.org/wiki/Visual_cortex 1 million nerve fibers for each eye Billions of neurons in the PVC Working together in PDP (parallel distributed processing) The PVC has a number of interlocking layered sub-regions, each of which respond to either color, shape, texture, motion, or depth. V1 and V2 provide inputs to two distinct processing systems. The what system Responsible for identifying objects in the environment. Helps identify if a pattern of light and color represent an identifiable object. The where system Responsible for determining the location of information in the world and guiding actions to grab it, or navigate around it or to it. What and Where Pathways What pathway sweeps forward from V1 and V2 along the low edge of both sides of the brain. Where pathway sweeps higher up on the brain and processes information about where objects in the world are located. Perceptual attention is called pre-attentive processing, but it is all about tuning. And most of it occurs in the sensory register. Tuning refers to the cognitive processes mobilized from the visual properties of graphics (salience) used to plan the next eye movement. In pedestrian terms: “pop out” “Pop out” requires a 30 degree orientation difference to stand out. Effects Due to feature-level CONTRAST. SIZE MOTION COLOR ORIETATION CONTOUR (CONVEX/CONCAVE) Creates visual distinctness Requires only ONE eye fixation. Perceived in 100 milliseconds Trying to find a target based on two features Size & color Orientation & contour Etc. Most visual conjunctions are hard to see. Conjunctions require attention; non-conjunctions do not. Time to do a conjunctive search increases linearly with the number of items. You have to pay attention to each item, one item at a time to bind the features. Neurons sensitive to more complex conjunction patterns are found farther up the “What” processing pathway. These neurons cannot be used to plan eye movements. If background is very homogenous, then a small difference is needed to make a feature distinct. The more the background varies in a particular feature channel (color, texture, orientation), then the larger the difference required to make a feature distinct. Color Size Shape Orientation Motion Contour To make something easy to find, make it different from its surroundings using a primary visual channel. To make several things easily searchable at the same time, use different channels. More than one feature can be changed on the same channel. Using more than 2 or 3 symbols to create “pop-out” is difficult. When aiming for pop-out, there are only three difference steps on each channel: 3 size, 3 orientation, 3 frequencies of motion, etc. What takes a fraction of a second with multi-feature designs can take several seconds with a consistent (say, color-only) design. Making visible enhancements is better than visible reductions. Increase symbol size rather than decrease it. Increase contrast rather than decrease it. Add extra parts to a symbol rather than take parts away. Manipulate motion in the periphery of the visual field. Motion should not be “shaking” per se, rather it should move into the visual field. Fast motion is annoying; slower motion is alerting The goal is to always to get a visual target in the vicinity of the eye’s detection field. From there, it becomes eligible for the next fixation. The bigger something is, the more it takes up in the detection field. Salience of visual channel targets create: HIERARCHICAL SEARCH STRATEGY. This poster shows multiple feature channels and visual searches. This duo tone poster has color as the top of the visual hierarchy. The blue and yellow have a pop effect, bold, bright colors on a black and white poster. These color features are also arrows that bring direction and motion to the poster. This keeps the eyes moving back an forth across the page. The bold black text boxes keep your eyes centered on the page. The dark irregular shape of the monkey then attracts the viewer. Color, motion, then shape. POSTED BY BAILEY KIMA http://f09323bnakano.blogspot.com/ Move and Scan Loop Eye Movement Control Loop Is the first step: involves orienting the head and trying to get the best viewpoint. Is the second step: involves executing eye movements around salient features and feature categories to map the locations in the whole design. Pattern Testing Loop Is the third step: involves finding a promising target and testing the pattern to see if it is the search target or not.