Dueling Monitors

A study out of the University of Utah and written up in the Wall Street Journal’s Business Technology Blog showed that bigger monitors led to faster completion of document editing and spreadsheet tasks. There were three screens used: an 18-inch monitor, a 24-inch monitor, and two 20-inch monitors. Versus the 18-inch monitor, people were 52% faster with the 24-inch monitor and 44% faster with the two 20-inch monitors.

Now this is expected - bigger is better. But what I’m interested in is the 6% improvement moving from two 20-inch monitors to a 24-inch monitor. Two 20-inch monitors provide much more screen space, but it’s not just size that matters.

Egly, Driver & Rafal (1994) were the first researchers to show the existence of object-based attention. That is, attention does not just form a spotlight (or zoom lens) that illuminates a particular portion of the visual field. Instead, attention can also mold itself to encompass a specific object, and there is a cost in switching between objects. The methodology they used was particularly ingenious.

The task was simply to detect a block that would appear in one corner of either rectangle (see below). That was it - press a button when you see the block (right most panel). Before the block, though, other things happened. In the second panel, you see that one corner of one object was also cued - it suddenly turned red. Participants did NOT have to respond to the cue - only to the block. So participants started a trial, received a red cue, waited, and then a block would flash. Reaction time was the primary measure; how long it took participants to press a button after the block flashed.

The red cue served to prime attention to a certain location. In the example above, the red cue and the block target were in the same location, and reaction time was fastest. However, sometimes, the block could appear elsewhere. There are two critical conditions:

1. The block was at the other end of the same object to where the cue was.
2. The block was at the same end of the other object to where the cue was.

What is critical to note is that, in these two conditions, the block and cue are the exact same distance apart. If attention was purely spatial and did not care about objects, reaction times in both conditions should be the same. This was not the case, though. Instead, participants were faster at detecting the block when it was located at the other end of the same object as the cue. The cue brought attention to that location, then attention spread to the entire object. Therefore, when the target appeared on the same object, reaction time was faster. When the target appeared on the other object, attention had to be switched, and this lead to slower reaction times.

So what does this all mean for the research at hand? Two 20-inch monitors are two separate objects. Even if they are both placed perfectly in your field of view, you will have to make eye movements and shift attention between the two monitors. This is going to slow you down more than if you had a single object (a single 24-inch monitor) in front of you. In this case, you don’t have to switch your attention between objects.

This does beg the question, however: what exactly constitutes an object? Two separate physical monitors are certainly an object. But if you have two spreadsheets open and are copying data from one to another, does that count as switching between objects? Would it be better to copy and paste inside one spreadsheet and then make one large copy and paste to the new spreadsheet right at the end? I don’t know the answers to these questions, but they are certainly worthy of research.