Cumulative cost of a few seconds

Currently, I’m on a project team that’s designing, building, and implementing call-centre software. You can probably imagine the call-centre experience from the customer side—we’ve all had our share of call-centre experiences. I’ve been looking at call centres from the other side—from the perspective of the customer-service agents and their employer.

I started by observing customer-service agents on the job. At the site I visited, the agents were using a command-line system, and the agents typed so fast that I couldn’t make sense of their on-screen actions. I signed up for several weeks of training to become a novice customer-service agent. This allowed me to make sense of my second round of observations, and appreciate how efficiently the agents handle their customer calls. It also helped me to identify tasks where design might improve user performance.

Wrap-up choicesFor example, after each call the agent decides why the customer called, and then, by scanning lists of main reasons and detailed reasons, “wraps up” the call, as illustrated. I measured the time on task; the average wrap-up task is nine seconds in duration.

It’s only nine seconds

Nine seconds may not seem long, but let’s make a few (fictitious but reasonable) assumptions, and then do a little math.

If the average call-handling time is five minutes, or 300 seconds, the 9 seconds spent on call wrap-up is 3% of the total handling time. A full-time agent could spend 202,500 seconds—that’s 56¼ hours per year—on call wrap-ups, assuming a 7½-hour workweek and no lulls in incoming calls. Since call volumes vary, there will be times when call volumes are too low to keep all agents taking calls. The customer-service agents have other tasks to complete during such lulls, but if we assume this happens about a third of the time, we need to round down the 56¼ hours accordingly. Let’s choose a convenient number: 40 hours, or one workweek per agent per year.

One workweek is 2% of the year.

Based on this number, a redesigned call wrap-up that takes only half the time would save one percent of the labour. Eliminating the wrap-up entirely would save two percent. That frees a lot of hours for other tasks.

A similar calculation on the cost side (n hours to design and implement changes) leaves us with a simple subtraction. Projected saving minus cost is the return on investment, or ROI. Comparing that number to similar numbers from other projects that we could tackle instead—the opportunity costs—makes it easy to decide which design problem to tackle.

Gestalt principles hindered my sudoku performance

Last week, while waiting for friends, I picked up a community newspaper in hopes of finding a puzzle to help me pass the time. I found a sudoku puzzle.

A sudoku puzzle consists of nine 3×3 squares, sprinkled with a few starter numbers. The player must fill in all the blanks by referring to the numbers that are already filled. A number can only occur once in each row of 9, each column of 9, and each 3×3 square.

I regularly complete difficult sudoku puzzles, but this easy one—more starter numbers makes the puzzle easier—was taking much longer than I expected.

I soon realised that my slow performance was due to a design decision by the graphic artist!

In the original puzzle, shown at left, the graphic designer used  shading  for all the starter numbers. In my reformatted version, on the right, I used shading to separate the 3×3 squares. Both puzzles also use thicker lines to separate the 3×3 squares.


The shading for starter numbers, on the left, is unfortunate because it interferes with the player’s perception of the nine 3×3 squares. Instead, players perceive groups of numbers (in diagonals, in sets of two, and sets of five).

I assume the designer’s intention was to help identify the starter numbers. Regardless of the designer’s intention, the human brain processes the shading just as it processes all visual information: according to rules that cognitive psychologists call gestalt principles. A sudoku player’s brain—any human brain—will first perceive the shaded boxes as groups or sets.


In sudoku, the grouping on the left is actually meaningless—and counterproductive. However, since the brain applies gestalt principles rather involuntarily and at a low level, the grouping cannot easily be ignored. The player must make a deliberate cognitive effort to ignore the disruptive visual signal of the original shading. This extra effort slows the player’s time-on-task performance.

You can check your own perception by comparing how readily you see diagonals and groups in both puzzles above. On the left, are you more likely to see two diagonals, two groups of five, and many groups of two? If you are a sudoku player, you’ll recognise that these groupings in the puzzle are irrelevant to the game.

If you like, you can print the puzzles at the top, and give them to different sudoku players. Which puzzle is faster to complete?

Interested in gestalt principles? I’ve blogged about the use of gestalt principles before.