Life with a digital speedometer

In my cognitive psychology class and on this blog, I have criticized the digital speedometer as not being as instantly useful as an analog speedometer, where you can quickly judge the angle of the needle and get a sense of how fast you are driving. However, buying a car is surprisingly emotional, and cognitive design principles can get thrown out of the window. In short: I bought a 2008 Honda Civic, and I’ve been driving it for about a week. How’s the digital speedometer?

It’s… usable. I don’t think it’s better than an analog speedometer. I can glance down and read the number, and interpreting my speed does not really take that much longer than an analog display. So I can get along just fine with it.

I do, however, take issue with why Honda made the change (source: Honda Press Release for the 2006 Civics, PDF version):

And they state the reason clearly again in the same press release:

The two-tier instrument panel positions priority gauges like the speedometer up high in the driver’s field of vision.

So Honda wanted to put the speedometer - critical information, to be sure - closer to the driver’s field of view. It’s a valid design choice, but why not move the analog speedometer upwards? My guess is that a traditional circular analog display would have been too large and would have interfered with driving. Therefore, as a compromise, Honda made the speedometer digital to save space. It doesn’t take up as much space as an analog version, and it has the benefit of looking pretty cool.

The problem with this is twofold. The first problem is that our peripheral vision is really poor. Our sharpest vision is only 1 degree of visual angle (the width of your thumb an arm’s length away is 1-2 degrees). Everything outside of that area is not very sharp. We can get some information out of it - maybe the angle of a line (analog speedometer) - but reading (digital speedometer) gets fuzzy. So Honda put the display closer to the driver’s field of vision, but made it more difficult to read by going digital. To make matters worse, there’s a concept called the Useful Field of View (Ball et al., 1988). Essentially, the more focused we have to be at a central task, the less we can pay attention to peripheral objects and events. Driving is an attention-heavy task, so we have even less attention to take in information in the periphery.

The end result? I still have to move my eyes away from the road and down in order to read my speed. Moving critical information closer to the driver’s visual field is good idea, but the implementation failed because of lack of knowledge about vision and cognition. By not understanding peripheral vision or the effects of attention to a central task, the repositioned digital speedometer fails at its goal of being better. It’s not a bad design, per se, but it does not improve the driving experience.

My first first-author publication!

Journal of Vision, Volume 7, Issue 12, Article 3. Page 1-10.

(The answer is: No.)

Of course, the appropriate question is likely: “What in the heck does that mean?” There’s been a lot of research since the late 1980s about what will grab your attention (Yantis & Jonides, 1988) and your eyes (Theeuwes et al., 1998) even if that event is task-irrelevant. Essentially, what visual things can happen so that it’ll distract you? In a standard task (and the one I used), you had to look for a uniquely colored circle and look at it. But sometimes, a new object would appear, or something would suddenly get brighter. The question is: how often do you look at the totally irrelevant event?

The event that has the best chance of capturing your eyes is when a new object abruptly appears on the screen. This sometimes happens in the real world when we’re not paying full attention to the world, and computer user interfaces use this all the time. The issue is that a new object abruptly onsetting consists of two things: a sudden visual change (new colors, luminance, etc.) and new object information (new semantic/meaning plus structural information). The question is which part of the abrupt onsets capture the eyes - the visual changes or the new object information. Proponents of the new-object theory (Hillstrom & Yantis, 1994; Yantis & Hillstrom, 1994) say that it’s the new semantic and structural information and NOT the new visual changes. There has been a lot of research looking at sudden visual changes alone (like a sudden increase in brightness), and the results have been mixed - capture of the eyes is not guaranteed (Franconeri & Simons, 2003).

So we wanted to see if new structural and semantic information without the sudden visual changes would capture the eyes. Besides using abrupt onsets, we also used object morphs, so a star would slowly morph into a circle. This presented new structural and semantic information while minimizing low-level visual changes. Turns out that sudden onsets (visual changes + new object information) attracted the eyes a lot (even though the target was elsewhere on the screen), but the morphs (new object information alone) didn’t attract the eyes in any special way.

From this, we can conclude that new object information must be accompanied by sudden visual changes in order to grab the eyes away from looking at the target. Admittedly, this paper primarily answers a theoretical question and doesn’t have immediate application. But think about how your computer tries to capture your attention: sounds, random messages popping up in front of you, new icons in the system tray, or maybe a sliding message coming from off the monitor. Which one of these capture your attention? And which one of those do you wish weren’t so annoying, or didn’t capture your attention all the time? That’s what the goal of this research is.

Wong, J. H., Peterson, M.S. & Hillstrom, A. P. (2007). Are changes in semantic and structural information sufficient for oculomotor capture? Journal of Vision, 7(12), 1-10.
doi:10.1167/7.12.3 (Journal of Vision website)