Earlier this week usability expert Jakob Nielsen (famous for his eyetracker studies) published the results of some research into the importance of page response times to user experience and perceptions of brand. In his words “users really care about speed”.
In Jakob’s assessment speed matters for two reasons:
- human limitations, espescially in the areas of memory and limitation
- human aspirations – fast interfaces make us feel like we control the computer (a feeling we like) whilst slow interfaces make us feel like it is the computer that is controlling us (not so good…)
In interviews Jakob has found that slow site speed is something which sticks in the minds of users when thinking about services they have used in the past. It can even become one of the brand values associated with a site.
Jakob proposes three response time limits:
0.1 seconds gives the feeling of instantaneous response — that is, the outcome feels like it was caused by the user, not the computer. This level of responsiveness is essential to support the feeling of direct manipulation (direct manipulation is one of the key GUI techniques to increase user engagement and control — for more about it, see our Principles of Interface Design seminar).
1 second keeps the user’s flow of thought seamless. Users can sense a delay, and thus know the computer is generating the outcome, but they still feel in control of the overall experience and that they’re moving freely rather than waiting on the computer. This degree of responsiveness is needed for good navigation.
10 seconds keeps the user’s attention. From 1–10 seconds, users definitely feel at the mercy of the computer and wish it was faster, but they can handle it. After 10 seconds, they start thinking about other things, making it harder to get their brains back on track once the computer finally does respond.
And he goes on to say that a 10 second delay will often make a user leave a site immediately and even a few seconds delay is enough to create an unpleasant user experience.
Speed is important for web services, period, and I’m returning to a theme I blogged about earlier this year. In the post I just linked to you will find a list of the most successful web services and the top ones are very fast. Additionally the sites whose fortunes are waning are the slower ones. I think speed is becoming more important, not least because Google started including response times in their search algorithm earlier this year.
To close – Jakob notes that the primary cause of slow page load times has shifted from big images to slow loading widgets.
Thanks to UX consultant Ian Collingwood for pointing me to this post. As he notes I’m not practising what I preach here – theequitykicker is slow to load, something I will work on as soon as I find the time.