The Psychology of Web Response Times

Hi!  I’m David Reich, and I’ve been interning at Matrix Group for the summer. I’ll be writing a post summarizing my experience here before I leave, but I’ve still got a bit more time, so today I’m posting some slightly more technical content. clock close up

One of the most interesting things I did for my internship was research. A few times, I was assigned to study and summarize certain aspects of web development.  This meant I got to learn about both my research topics and, just as usefully, how to write professionally.

Recently, I did some research about design and psychology of response times in application development. Not just web app development, either – the principles that apply to Matrix Group’s products are just as applicable to other types of interaction between humans and systems like games, telephones, or even conversations.

Temporal Cognition: how long is too long?

When interacting with a well-designed piece of software, the user enters into a ‘conversational’ mode with it. Users receive useful responses just as quickly as in a verbal interaction, and feel just powerful as when manipulating physical tools. The application moves at the same speed they do, and never interrupts their thought processes, so they can reach a productive state of ‘flow’.

That’s for a well-designed application. What, then, is the quantitative difference between software that works with the user and software that breaks their concentration? In 1993, Jakob Nielsen described three boundaries that separate the two. George Miller, 25 years before, went into greater detail with a similar conclusion. In the context of user-interface design, that research might seem ancient, but in psychology it isn’t. People today have the same temporal cognition that they did forty years ago. Miller’s research isn’t outdated; it’s categorical.

First Boundary

Nielsen’s first boundary lies at 0.1 seconds.

A tenth of a second: this is time that it should take for a character to appear on the screen after being typed, for a checkbox to become selected, or for a short table to sort itself at the user’s request.  When it takes less than a tenth of a second for the user’s command to be executed, the user feels like they’re in direct control of the software – as direct as flipping a light switch or turning a doorknob.  People won’t even register waiting times of less than 0.1 seconds.  If an application takes half a second to run a JavaScript function, though, users will perceive the computer taking control.

Second Boundary

The second boundary is at 1 second according to Nielsen, but 2 seconds by Miller. In either case, it’s the point at which the user is in danger of losing their productive sense of flow. When the user is forced to wait for less than 2 seconds, they’ll notice a delay, but it probably won’t feel unnecessary or distracting. For delays between 0.1 and 2 seconds, a progress indicator is unnecessary, and might even be distracting.

Third Boundary

Neilsen and Miller also disagree over the time of the third boundary. Nielsen puts it at 10 seconds, and Miller at 15. This third boundary is the point when the user loses focus on the application and shifts their attention to something else. It should be avoided whenever possible. Times in between the second and third boundaries – between 2 and 10 seconds – should have some sort of progress indicator.  A spinning cursor is appropriate for times in the lower end of that range. For times above 10 seconds, assume that the user’s focus on their task has been lost, and that they’ll need to reorient themselves when they return to the application. A progress bar that either estimates the percentage of completed processing or provides some feedback about the current task is vital. Waiting times of longer than 10 seconds should only be used when the user has just completed some task, and the user should be allowed to return at their own convenience.

Key Landmarks

Those three boundaries – 0.1, 1, and 10 seconds – are the key landmarks of responsiveness for web applications. I would attribute Nielsen and Miller’s disagreement over precise numbers to the vagueness and context-dependency of the entire question. Nielsen’s numbers, powers of ten, are prettier and easier to remember, but Miller’s may be more psychologically accurate.

A lot of this sounds very academic and theoretical, but it could be meaningful for success of a web-based business: according to WebPerformanceToday.com, 57% of consumers say that they’re likely to abandon a page if it takes more than three seconds to load.

Sources:

Do you agree with these studies? How long do you wait for a task/web page to complete or load?