Visual Information Processing System

- By understanding a little about our visual perception system, and it’s limitations, we can ensure we design effective data visualisation that do not deceive.

Reality is a Construct

• Visual illusions remind us of the limitations of our visual perception system and how our brains construct reality.

Preattentive Processing

• What features of the following image “pop-out” to you?

Preattentive Processing Cont.

• What draws your attention?

Preattentive Processing Cont. 2

• Preattentive processing is the degree to which a visual object is made available for our attention (Ware, 2013)
• Many features are known to be preattentively processed:
  • Orientation
  • Curved/straight
  • Shape
  • Length
  • Size
  • Colour
  • Light/dark
  • Enclosure
  • Convex/Concave
  • Addition

Preattentive Processing Cont. 3

Gestalt Laws

• Gestalt laws attempt to explain the way humans recognise visual patterns. In this workshop we look at the following laws and how they relate to data visualisation:

  • Proximity
  • Similarity
  • Connectedness
  • Continuity
  • Symmetry
  • Closure
  • Figure Ground Principle
  • Common fate

Proximity

• Objects close or clustering together are perceptually grouped.

Proximity Example

Similarity

• Objects of similar characteristics (e.g. size, shape, colour) are grouped.

Similarity Example

By Chire - Own work, CC BY-SA 3.0, Link

Connectedness

• More powerful than proximity, colour, size or shape. Objects connected by lines demonstrate relationships between objects.

Connectedness Example

Continuity

• This law predicts that we are inclined to perceive objects from elements that are smooth and continuous, versus irregular and jagged.

Continuity Example

Symmetry

• We tend to group symmetrical objects together.

Symmetry Example

• ABS Population Pyramids

Closure

• Closure refers to our tendency to “fill in the gaps” when we see incomplete patterns that resemble familiar shapes and objects.

Closure Example

• Overlapping density plots

Figure Ground Principle

• The figure ground effect tells us that smaller objects within a figure are interpreted as the foreground, while larger objects make up the ground.

Figure Ground Principle Example

• Beautiful plotting in R?

Common Fate

• Objects perceived to be moving in the same direction are grouped together and share a common path.

Common Fate Eample

• Hans Rosling’s Bubble plots

Change Blindness

• Breaks in our attention can make us insensitive to changes in our environment.

• How can we use our understanding of change blindness to improve our visualisations?

Inattention Blindness

• Focusing our attention can cause other things in the environment to go unnoticed.

• How can we use our understanding of inattention blindness to improve our visualisations?

Visual Variables

Visual Comparison Accuracy

Activity 2 - Deconstruct

• Working with your partner or in a small group, discuss the perceptual issues associated with pie charts.

Quick Quiz 2

• Let’s do a quick revision quiz:
  • Visit https://b.socrative.com/login/student/
  • Room Name: DATAVIS
  • Enter a nickname
  • We will work through each question as a group