N328 Visualizing Information Week 3: Visual Perception Khairi - PowerPoint PPT Presentation

N328 Visualizing Information Week 3: Visual Perception Khairi Reda | redak@iu.edu School of Informa5cs & Compu5ng, IUPUI

Last week…

Attribute/Variable Types ✦ Categorical (Nominal, Qualita7ve) A finite set of categories No implicit ordering between categories ✦ Ordered •Ordinal Implicit ordering between categories/levels, but no clear magnitude difference. Can compare and determine greater/less than •Quan7ta7ve Meaningful magnitude Can do arithme5c

Quan7ta7ve Data Interval vs. Ordinal ✦ Interval •Zero does not indicate an absence of detectable measurement •We can determine distance between measurement, but not propor5ons •Example: temperature, dates ✦ Ra7o •The posi5on of zero indicates there is nothing of the measured en5ty •Can determine ra5o and propor5ons •Example: weight, age

This week Fundamentals of Visual Percep5on and Cogni5on

Reading materials Quiz • Used to mark aTendance (1 point) • 10 minutes • Pass code: lemon

Perception vs. Cognition Percep7on Iden5fica5on and interpreta5on of physical sensory input Cogni7on The processing of informa5on and applying knowledge Recording and retrieving informa5on from memory Percep7on: Hearing someone speak Cogni7on: Understanding words, remembering informa5on Based on a slide by Alex Lex

Perception vs. Cognition Perception Cognition •Object recogni5on •Rela5onship between objects •Eye, op5cal nerve, primary visual cortex •Remembering shapes or •Basic visual features (e.g., edges, paTerns orienta5on, shapes) •Learning new shapes •Unconscious •Problem solving •Deliberate •Requires aAen7on Based on a slide by Alex Lex

The boundary between perception and cognition is hard to delineate Perception -> cognition Cognition -> perception

Faces in Things

Take home point What we see is influenced by visual features our brain perceive (boTom-up) and by what we know beforehand (top-down)

The human visual system Illustration from Wikipedia

The human visual system https://www.researchgate.net/figure/Processing-steps-of-the-visual-stream-a-The-cellular-organization-of-the-retina-from_fig1_233971662

The human eye light electricity http://www.fortworthastro.com/images/eye_xsection_01.jpg

rods ~120 million highly-sensi5ve to light not sensi5ve to color good for low-light vision cones ~5-6 million sensi5ve to color require good ligh5ng sharp vision ganglion cells “Structure of the Mammalian Retina”, Ramon y Cajal Based on a slide by Alex Lex

Electron microscopy of photoreceptors Wandell, “Foundations of Vision”

Cones types HyperPhysics, Georgia State University

Cone distribution by pigment color blindness normal vision (red deficiency) Wikipedia

Density of rods/cones E. Goldstein, “Sensation and Perception” Adapted from Lindsay & Norman, 1977 Via Miriah Meyer

C. Ware Visual Thinking for Design

Vision Human vision does not work like a camera The eye makes a series of fixa7ons and saccades fixa7on: maintaining gaze over a single loca5on ( 200-600ms) saccade: movement between loca5ons 20-100ms Based on a slide by Alex Lex

Visual Illusions

Via Miriah Meyer

Via Miriah Meyer

Cornsweet illusion

Visual perception is relative

Visual perception is relative Differences in color are rela5ve

Visual perception is relative Differences in contrast is rela5ve

Visual perception is relative Color interac5on Wong 2010 Via Miriah Meyer

Visual perception is relative Sizes are rela5ve (Ames room)

Take home point Our visual system see differences, not absolute values. Based on a slide by Miriah Meyer

Design critique http://tinyurl.com/6mu8h63 • What is the visualiza5on about? • What data is represented in the visualiza5on? And how? • What are the interac5ons used? • What ques5ons can we answer with the visualiza5on? • Do you like the visualiza5on? • Are there any improvements that can be made to the design?

POPOUT

which side has the outlier?

which side has the outlier? C. Healey, 2007

which side has the outlier? C. Healey, 2007

which side has the outlier? use a single popout channel at a time (e.g., either difference in color or shape alone) to draw attention C. Healey, 2007

Popout channels no popout C. Ware “Information Visualization”

Semantic Depth of Field C. Ware “Information Visualization”

Semantic Depth of Field R. Kosara

Popout / pre-attentive processing • Very fast at grabbing aTen5on (less than 200 milli seconds) • Popout elements have to be salient compared to surrounding • Elements that are a conjunc7on of mul5ple channels ogen do not pop out

How does pre-aAen7ve processing / pop outs work? We don’t know for sure, but there are some theories: https://www.csc.ncsu.edu/faculty/healey/PP/ index.html#Preattentive_Theory

Take home point We can easily see objects that are different in color and shape, or that are in mo5on Visual features must be carefully designed. Conjunc5ons must be avoided, if popout is desired Use color and shape sparingly to make the important informa5on pop out Based on slides by Miriah Meyer & Alex Lex

Gestalt grouping principles

Gestalt grouping principles gestalt : form in German “The whole is other than the sum of its parts” Our brain has innate capacity to see paTerns that transcend the visual s5muli the produce them

proximity Andy Rutledge, “Gestalt Principles of Perception”

proximity Alex Lex

proximity B. Wong, “Gestalt Principles, I”

similarity B. Wong, “Gestalt Principles, I”

similarity Andy Rutledge, “Gestalt Principles of Perception”

connectedness Ware, “Information Visualization”

link surface outline enclosure Alex Lex

A liAle experiment… How many groups do you see? color size shape proximity similarity similarity similarity Based on a slide by Alex Lex

A liAle experiment… How many groups do you see? color size shape proximity similarity similarity similarity Based on a slide by Alex Lex

A liAle experiment… How many groups do you see? color size shape proximity similarity similarity similarity Based on a slide by Alex Lex

grouping B. Wong, “Gestalt Principles, I”

grouping

grouping Jorge Camoes Via Miriah Meyer

grouping - common fate

closure

closure

figure / background Mariah Meyer

Gestalt principles similarity: objects that look like each other (in size, color, or shape) are related proximity: objects that are visually close to each other are related connections: objects that are visually connected are related closure: we see incomplete shapes as complete figure / ground: elements are perceived as either figures or background common fate: elements with the same moving direc5on are perceived as a unit Mariah Meyer

next week… color perception