## Four numbers say little, even on a busy chart

##### Dec 03, 2012

Reader Robert J. calls this a "really bad" chart (link). The data-ink ratio, he notes, is horrible.

The message of the chart can be stated in one or two sentences. And it's not clear what the other items are buying us. I usually love text annotations but three for this simple chart are too many.

***
The biggest issue I have are the axes. What is left unsaid is whether the inability to perceive outside the zone of human ability is inconvenient or not. What's missing is a histogram of the stimuli. I'd guess that the distribution is uneven, and there is a concentration inside the humanly perceptible zone. It would be helpful to include what type of stimuli exists at different frequency bands to illustrate what we are missing.

A different comparison that helps interpretation is other mammals. What is the range of perception of dogs, pigs, cows, etc.?

We should also think carefully before putting these two independent quantities onto the same chart. The rectangular region is merely a construct of the chart designer. In fact, the size of the rectangle is arbitrary as the scales on either axis can be made however large we want.

You can follow this conversation by subscribing to the comment feed for this post.

Also, isn't the underlying message of the graph kind of questionable? What is the rationale for comparing these two variables?

I think it's important to note that the chart's intent was as much entertainment as anything else, for starters.
(the source is a web comic afterall)

I don't think the chart is that bad, really, though I do very strongly agree that the useful part would noting the ranges for other animals and how they compare.

Plotting the two attributes on one chart may not be the most scientifically appropriate way to display these measures, but again - as an entertainment piece, it does well enough as a means of showing the limits of human perception.

what jlbriggs said. adding in histograms for stimuli would make for lots of busyness, losing the point; but including other animals would be cool for comparison sake (and would highlight whether our 'limited' nature is really all that limited).

I am with jlbriggs too. When I first saw this in the context of being a web-comic, I thought it was great, they took a two sentence statement, and made an entertaining visual from it, like thisisindexed.com

I can also see your possible point that promoting graphics like this means people need to be un-taught from thinking that visuals like this are useful in a more rigorous setting, making this graphic useful for teaching what not to do in other situations.

- Why all the hating? The point is to notice all the blackness 'Look at how much information we -don't- get!'. Showing other animals' ranges would be a great graph but one with a very different story.

- The axes are equivalent log scales. that's usually a good practice.

- So the emphasis of the ranges has a bunch of thick dashes. Big deal. Lighten them up if they take up too much ink. Or some other way to emphasize the smallness of the range with less ink.

- The only misleading thing here is that we have two sensors for aural frequencies but many, many (~130 million) visual receptors. -Very misleading-. But that's not a data-ink problem.

Except for the last point, this is a kick-ass graph. I learned stuff from it without trying hard. Isn't that the point?

Also with jlbriggs. This post borders on self-parody.

But really 'all you see' is the whole horizontal segment, and 'all you hear' is the whole vertical segment. We don't need to both see AND hear something to perceive it.

Rosie is right, that it should be the whole horizontal band and the whole vertical band, not the intersection.

My concern is that the two are unrelated. Sound is sound, and light is light. I think a more sensible choice would be to pick one of these and point out how little of it we experience; light is the more surprising one here as we experience a very small range, even including heat. By contrast we can experience sound from a few hertz as a rumble, all the way up to the limit of hearing in the kHz.

There isn't really a sensible upper or lower limit for sound, because a mass ripple across a galaxy could still be called sound, and that's going at what, nanoHertz? FemtoHertz? But it's not even useful to see it as an oscillation at that level.

Without reasons to set the upper and lower bounds of the chart, there's no reason to point out an abstract gap in our senses; if all the useful sounds happen in roughly the range of human hearing, that's a good thing, isn't it? And arguably since sound is largely unencumbered by frequency-dependent losses in the media around us, our hearing is pretty broad and complete compared to the vibrations available.

Light, however, is beset by emission and absorption spectra from the black body radiation at the sun through the atmosphere, water, etc. We evolved to experience the colours of nature (lots of green!), but now spend a lot of time looking at non-natural materials, which we could be experiencing more broadly. We are also filling up the airwaves with all sorts of EM signals below visible frequency, which we could arguably also enjoy; the patterns of FM radio stations playing on the wall outside, the Wifi signal spilling through that bit of stud wall.

Evolution may help us, or we may help ourselves; some women are believed to be tetrachromats already (different cone genes on each X chromosome), but we may turn to modifying ourselves biologically and/or mechanically (pan-spectral imaging visors?).

I liked the Alt text on the webcomic "Adding a third dimension of smell proved too difficult."

Normally the critiques here are very good, but on this one...jeesh, talk about missing the forest for the trees. You're seriously worried about "the rationale for comparing the two variables?" Or the rigor of graphic representation? This isn't from Nature. This blog, not the graphic, is bordering on self-parody. Lighten up! Take a moment to wonder about the universe beyond our unaided perception, which is the true intent of the graphic. That's also why the great unknown is all black here.

There's another clever musical/visual reference in there too - the "all you hear and all you see..." caption I think is a reference to "And all you touch and all you see is all your life will ever be" from Pink Floyd's 'Breathe', which was on Dark Side Of The Moon (the album with the black cover showing light refracting through a prism) - which is what this chart reminded meof before I'd even read the caption.

The comments to this entry are closed.