Why are figures hard to read?

In a previous post, I talked about how figure legends are quite useless. But that got me thinking about figures more generally. Gautham and I have both been talking about how sometimes we read papers first without even looking at the figures. I like this style of reading because it allows you to pay attention to the authors' arguments without interruption. Of course, the problem is that you don't actually see the data they're referring to. But if you trust that their interpretation of their graph or picture or whatever is correct (otherwise they wouldn't be showing it, right?), then there's really no point in looking at the figure, right? Hmm...

So why am I avoiding figures? I think the reason is that there are a lot of cognitive hurdles to doing so. Many papers will have some sort of an interpretative statement, like this "Knocking down the blah-1 gene led to a substantial increase in cells walking to the side of the plate and turning purple (Fig. 2D)." Okay, but then you look at the figure, and it will probably have some sort of bar graphs of knockdown efficiency and some cell-walking-turning-purple assay readout. Then I have to think about what those charts mean and how they did the assay and whether that makes sense and... you get the idea. It requires a lot of thinking, and by the time you understand it, I defy anyone to go right back to the main text and regain their previous train of thought.

What to do? Well, this seems to be far less of a problem when you're giving a talk. Why? I think it's because you have the opportunity to spend time with the figure and explicitly show people what you want them to get out of it as an integrated part of your narrative. In a paper, I think one of the things we could do is to adopt things like sparklines (ala Tufte), which are inline graphics. Here's an example lifted straight out of Wikipedia: The Dow Jones index for February 7, 2006 . Let's take our previous example. What if I said something like "Knocking down the blah-1 gene  led to a substantial increase in cells walking to the side of the plate and turning purple  . Simple and informative, and inline, so there's no cognitive interruption. (Note: they came out bigger than I wanted, but it's hard to deal with this pesky Blogger interface.) Does this have all the information that a figure would have? No. But it conveys the main point. And probably with slight larger graphics, you could include a lot of that information. As it is with most figures, there's so much missing information anyway in terms of how one actually made the figure that it's not like it's all that complete to begin with. The best way to deal with that is if we adopted a writing style in which we didn't just give an interpretation, but actually took the time to explain what we did. That's hard within the writing limitations imposed by the journals, though.