The Functional Art by Alberto Cairo


The Functional Art

The Functional Art: An introduction to information graphics and visualization book in three Sentences:

Alberto Cairo in his The Functional Art book weaves visualization theory and techniques with real applications and critiques about existing visualization projects. In the first part of the book, Cairo explains good graphic techniques and strategies, how to create eye-pleasing graphics and, most importantly, how to use data visualization to tell a story. The second part of the book is more about the eye-brain connection and how we as humans perceive different shapes, colors etc.

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The Functional Art Summary

In Ben Shneiderman words, “The purpose of visualization is insight, not pictures.” 

  • Our brain has the ability to create and understand visual representations with different degrees of abstraction: graphics that encode data, concepts, connections, and geographical locations.
  • The human brain has dozens of regions related to visual perception: densely interconnected groups of neurons devoted to the processing and filtering of information that we collect through our eyes.
  • The brain doesn’t just process information that comes through the eyes. It also creates mental visual images that allow us to reason and plan actions that facilitate survival. 
  • The first and main goal of any graphic and visualization is to be a tool for your eyes and brain to perceive what lies beyond their natural reach.

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⚡Edward Tufte, arguably the most influential theoretician in visualization and information design and information design defined the relationship between form and function succinctly:

Effective analytic designs entail turning thinking principles into seeing principles. So, if the thinking task is to understand causality, the task calls for a design principle: “Show causality.” If a thinking task is to answer a question and compare it with alternatives, the design principle is: “Show comparisons.” The point is that analytical designs should be decided on how the architecture assists analytical thinking about evidence.


Art and Communication

  • An information graphic can explain many different things once (novelty) or it can explain the same things several times, by different means (redundancy). Striking a balance between novelty and redundancy is critical.
  • Novelty is important to avoid boring your readers, but a certain level of redundancy is necessary if you want to be understood.
  • The complexity of a graphic should be adapted to the nature of your average reader.

Minimalism and Efficiency

⚡A cherished notion of Tufte’s is a principle of efficiency: A visual design project is good if it communicates a lot with little. In his own words, in his principles of graphic excellence:

  • Graphical excellence is the well-designed presentation of interesting data—a matter of substance, of statistics, and of design.
  • Graphical excellence consists of complex ideas communicated with clarity, precision, and efficiency.
  • Graphical excellence is that which gives to the viewer the greatest number of ideas in the shortest time with the least ink in the smallest space.
  • This efficiency principle is defined with more precision by Tufte as the data-ink ratio: a measurement of the amount of ink that is used to represent data in a chart.
  • Tufte defines data-ink elements as those that cannot be removed without destroying the integrity of the presentation. The other items, those that amount to decoration, can be eliminated because they are either redundant or they distract the reader from what really matters.

Data-ink ratio = Ink that encodes data / Total amount of ink used to print the graphic.


Presentation and Exploration

⚡A data visualization should only be beautiful when beauty can promote understanding in some way without undermining it in another. Is beauty sometimes useful? Certainly. Is beauty always useful? Certainly not.  -Stephen Few.

  • The first step to finding the middle ground between radical minimalism and a more playful approach to information graphics and visualization is to remember that a good graphic realizes two basic goals:  It presents information, and it allows users to explore that information.
  • In other words, an information graphic is a tool for the designer to communicate with readers, and a tool for readers to analyze what’s being presented to them. 

The Eye and the Visual Brain

  • Vision is the result of mapping your environment based on the aggregated information your eyes obtain from multiple fixations. But the eyes don’t fix on random sections of the landscape. They are attracted first to certain features before they move to others. They prioritize.
  • Not all of what stimulates the cells in your retina is processed with the same level of detail in the brain, and not all of what the brain perceives reaches a conscious level and becomes rational understanding.

Choosing graphic forms

⚡In 1984, William S. Cleveland and Robert McGill, statisticians published a groundbreaking paper that proposes basic guidelines for choosing the best graphic form to encode data depending on the function of the display.

The authors designed a list of 10 elementary perceptual tasks, each one a method to represent data, and ranked them according to how accurately the human brain can detect differences and make comparisons between them.

The tasks are grouped according to how well you can perceive differences in the data by using them. The tasks include:

  • Position along a common scale
  • Position along nonaligned scales
  • Length
  • Direction
  • Angle
  • Area
  • Volume
  • Curvature
  • Shading
  • Color saturation

The important criterion for a graph is not simply how fast we can see a result; rather it is whether through the use of the graph we can see something that would have been harder to see otherwise or that could not have been seen at all.



⚡In order to understand perception, you need first to get rid of the notion that the image at the back of your eye simply gets “relayed” back to your brain to be displayed on a screen. Instead, you must understand that as soon as the rays of light are converted into neural impulses at the back of your eye, it no longer makes sense to think of the visual information as being an image. We must think, instead, of symbolic descriptions that represent the scenes and objects that had been in the image. -V.S. Ramachandran

  • You need to build a solid backbone for your information, a reading path, an order, and a hierarchy before you lock yourself into a style for your display.
  • The structure is the skeleton and muscles of your graphic; the visual style is the skin. With no bones to support it, the skin of your project will collapse.
  • You should not proceed to develop a graphic on the computer before you’ve devised a precise outline of the graphic’s elements and how they relate to one other.
  • Planning your content in advance saves a lot of time down the road.


Structuring graphics

Ben Shneiderman, defined what he called the Visual Information-Seeking Mantra: “Overview first, zoom and filter, then details on demand.”

  • First, present the most important figures or the most relevant points. Then, allow readers to dig into the information, explore, and come up with their own stories.
  • Some of your infographics will necessarily be linear; that is, each step of the presentation will depend on understanding the previous one. 
  • Other graphics will be non-linear, giving readers choices for navigating the information using buttons, scrollbars, and other means.
  • In either case, you would introduce the topic using a clear headline and a short intro. Don’t throw tons of data at readers if you don’t explain first what it means.


When Connie Malamed asked Alberto what he wanted readers to take away from this book. He said that he has a double goal.

For beginners, I would like to show them that starting a career in graphics is not that difficult. Even if you are just interested, learning some basic visual representation skills may be very helpful. Many “non-visual” people get overwhelmed by the number of tools and languages, so I tried to convey my own low-tech approach to graphics.”

For the professionals, I tried to give them some perspective on how to think about graphics. Many designers focus on the aesthetic level before they think about the information, structure and forms their data should adopt. I don’t leave aesthetics aside, as I am a sucker for beautiful graphics. But in the book, I repeat that you should care about depth, structure, honesty, and clarity before you think about what color palette or typefaces to use. I also try to provide a broad and flexible framework for deciding what graphic forms to use in each case.”


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