Visual Perception CS 43905390 Fall 2014 Shirley Moore

Visual Perception CS 4390/5390 Fall 2014 Shirley Moore, Instructor September 8, 2014 1

Announcements • Dr. Moore’s office hour today is at 2 pm instead of 3 pm • CS Seminar, Dorian Arnold, UNM, 3 -4 pm Thursday Sept 11, “Scalable Middleware and Tools for High Performance Computing”, location TBD • HW 1 grades posted on Black. Board • Reminder: NSF/Popular Science Vizzies deadline Sept 30 2

From last class: Class Exercise 2: Location Data for the Map • Now let’s draw a red circle in the center of each state, with the size of the circle representing the state’s population. • Download the following two files and add them to the sketch: – http: //benfry. com/writing/map/locations. tsv – http: //benfry. com/writing/map/Table. pde – The second file contains code to read the data in the first file into a table. • Find population data on the Web and add the data to the sketch. • Draw the required circles on the map. • Add rollovers to show the state name and population when the mouse hovers over it. 3

The Human Eye 4 Image credit: http: //sciencewithme. com/learn-about-the-human-eye/

Retina with Rod and Cone Cells Image credit: http: //blog. eyewire. org/behind-the-science-fundamentals-of-the-retina/ 5

Distribution of “brain pixels” (Ware 2008) 6

Visual Cortex Image credit: http: //mikeclaffey. com/psyc 170/notes-vision. html 7

Visual Attention • We apprehend only a tiny amount of the visual information in our surroundings. • We sample the visual world on a need-toknow basis. • Visual attention consists of a series of visual queries – eye movements – pattern matching • Both bottom-up and top-down processing 8

Stages of Visual Cognition • Feature processing – Parallel processing of visual field by billions of neurons in V 1 area of visual cortex – Orientation and size, red-green, yellow-blue, direction of motion • Pattern construction – Visual space divided into regions – Chains of features connected to form contours • Object formation – Features and patterns distilled into visual objects – About three visual objects can be held in visual working memroy at one time. – Objects linked to non-visual information 9

Implications for Visual Design • Analyze visual tasks • Break tasks down into visual queries • Design displays so that visual queries can be processed correctly and quickly for every important cognitive task – Support the most important and frequent visual queries with visually distinct symbols • Example: public transit map 10

Visual Distinctness • Based on early low-level feature processing system • If we are looking for something small, we can only see it when we are lookng at it. How do our eyes get directed to the right location – Visual scanning – Biased shouting mechanism • Want target to be distinct in some feature channel of the V 1 area • Hard-wired in the brain, not learned 11

Basic Feature Channels 12

Do any circles appear distinct? 13

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Find the symbol that is different 18

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Conjunction 20

Visual Conjunction • Trying to find a target based on two features • Most visual conjunctions hard to see • Neurons sensitive to conjunctive patterns are farther up the processing pathway and cannot be used to plan eye movements. 21

Motion • Motion generates an orienting response. • Most powerful orienting response is elicited by things that move into the visual field. • Hard to suppress orienting response – use sparingly! 22

Visual Search Process – Where’s Waldo? Image credit: http: //eyetrackingupdate. com/2010/02/01/where%E 2%80%99 s-waldoeye-tracking-only-registers-half-of-the-visual-search-process/ 23

Preparation for Next Class • Read Ware Chapter 4 and Munzner Chapter 10 on Color • Continue working on Lab 1 – Bring questions and problems to class on Wednesday! 24