Good behavior, health and longevity play no role in breed popularity; these were the findings of a recently published study. In addition to being open access there are 3 more articles discussing the details in the “related links” section so I won’t reiterate what has been said. Instead I was more intrigued by the way the data was presented. It was unimaginative, confusing and uninformative.
The first problem is the lack of consistent order in C-BARQ variables. Table 1, Figure 1 and Figure 2 all have different order. There is no reason why for this. If we want to refer to a description or compare tables and figures there is no easy way to do it.
Figures 2 and 3 could also benefit from a splash of color or even just an informative glyph. Given that most of the results are not significant (statistically speaking), something to highlight the significant results would have made for a better figure.
“The representation of numbers, as physically measured on the surface of the graphic itself, should be directly proportional to the quantities represented.” - Edward Tufte
A rose diagram (petal /polar area / radial bar / sunburst) – most notably associated with Florence Nightingale – is a poor choice to visualise CBARQ data.
The layout is deceptive; by dividing the circle into 14 equal segments, the authors seem to imply that all traits (at their maximum) are quantitatively equivalent. I can only conclude from the above that beagles and dachshunds were dead – they have zero ENERGY – and are dobes so much more energetic than goldens? TRAIN a dachshund? Not likely, they score zero for trainability. The graph paints a distorted picture of breed traits, large values are exaggerated and small values are rendered invisible.
The use of areas to represent linear values is ready-made for misinterpretation because we are not very good at comparing areas and using a pie graph would not help matters either because we are equally bad at comparing angles. It’s also counter-intuitive to think a 7.07 x 7.07 cm square is half the size of a 10 x 10 square and the same is for rose diagrams with data being proportional the root of the radius. [see Lie factor and Data-Ink ratio]
There is a better way to show the data. Originally designed to visualize genomic data, the Canadian software package Circos has proven useful across a number of disciplines. The circular format offers a number of advantages noted in the website including the reduction in memory load.
The figure below illustrates a very simple table and the Circos output; see here for an in-depth explanation of other options.
In the figure below, specific to fear/ aggression, we can see stranger aggression (STRAGG) is most prominent in Dachs and just by ribbon size alone we can see Golden, Poodle and Labrador score lowest in fear and aggression.
Here I take the same data in Figure 1 and visualize it using Circos. To ease comparison I kept the same order and color scheme. This format also allows us to compare several breeds at a glance.
And we can also visualise each individual breed without losing the smaller values or exaggerating larger ones.
I think Circos format offers an appealing way of displaying data; it has strong data-fidelity plus it allows us to compare a number of breeds in a single graph. It’s not the only way to visualize breed temperament but it’s a good one. One thing is certain, rose petal graphs should never be used again…. for anything![No 3D graphs either]
They say there are “lies, damn lies and statistics”, I like to add bad graphs to that list.
- What makes a dog breed popular? (Stefano Ghirlanda is one of the study’s authors)
- Fashion vs. Function in Cultural Evolution: The Case of Dog Breed Popularity (Alberto Acerbi is one of the study’s authors)
- Why Are Some Breeds of Dog More Popular Than Others? (Companion Animal Psychology)
- On the truthfulness of petal graphs for visualisation of data (PDF at http://www.nik.no/2012)
- Naomi Robins (Forbes)
- Poor visualization can do more harm than good (Visual.ly)
- Misleading graph (wikipedia)
Ghirlanda S, Acerbi A, Herzog H, Serpell JA (2013) Fashion vs. Function in Cultural Evolution: The Case of Dog Breed Popularity. PLoS ONE 8(9): e74770