Mobile Web Stress: Understanding the Neurological Impact of Poor Performance [SLIDES]


Earlier today, I had the privilege of speaking at Velocity Santa Clara on a topic near and dear to my heart: the mobile user experience. I presented research we conducted at Radware that I’m really excited about.

By now, most of us have internalized the fact that slow pages hurt mobile user metrics — from bounce rate to online revenues to long-term user retention. At Radware, we wanted to understand the neuroscience behind this in order to get a 360-degree view of mobile performance, so we engaged in the first documented study of the neurological impact of poor performance on mobile users.

Based on similar research performed on desktop users, our study [you can download the report here] involved using a groundbreaking combination of eyetracking and electroencephalography (EEG) technologies to monitor neural activity in a group of mobile users who were asked to perform a series of online transactions via mobile devices. In our study, participants were asked to complete standardized shopping tasks on four ecommerce sites while using a smartphone. We studied participants during these tasks, both at the normal speed over Wifi and also at a consistently slowed-down speed, using software that allowed us to create a 500ms network delay. (IMPORTANT: The participants didn’t know that speed was a factor in the tests; rather, they believed that they were participating in a generic usability/brand perception study.)

Some highlights of our findings:

  • Frustration peaks were most prevalent during the browsing and checkout phases.
  • Users experienced frustration peaks of up to 26% at critical points in the transactions.
  • Faster pages correlated with increased user engagement. (That’s a good thing.)
  • Slowness affected the entire perception of the brand, even non-performance aspects of the site such as content, design, and navigation.
  • Users experience “web stress” even under ideal mobile browsing conditions.

The positive takeaway from this is that there’s a clear opportunity for companies to improve the user experience — and as a result strengthen their overall brand — by investing in performance optimization.

My slides are below. If you have any questions about our research and findings, I’d love to hear them.


  1. Its very common for developers to overlook the impact of performance as merely speeding up page load speed etc. and not from a user experience and conversion prospective. In the past myself included.

    On a recent client project on their new e-commerce build we initially improved performance compared to the old site, primarily from the code base and new server initially. this helped move conversion rate from 0.5% average to 1%.

    We then started optimising resources and deliverability of resources and again improving speed of the site which again has helped the conversion rate increase and bounce / exit rates decrease giving the user a much better experience.

    The other major factor is the new responsive layout compared to the previous site that had no mobile presence which again impacted performance in a major way and has proven to give the end user better performance and a much better experience.

  2. I have to say this. As developers, we’re not always at fault for slower mobile sites. Many developers are viewed in companies not as creative people, but as dumb implementors whose job is to do whatever the managers tell them to. It starts with designers and CEOs and marketers who dictate certain slow things. Designers want to flex their ego and demand that 4 different kinds of fonts are included in the design or that designs are loaded with tons of extra images. Then CEOs get involved and demand that the design adds certain things just to put their stamp on the process. Then marketing guys demand that the entire page has 20 times more content than needed for SEO purposes and tons of social media widgets to get more likes. This is such a big focus that there are just a ton of companies listed at who only focus on this. Add up all of these factors together, add too many cooks to the kitchen, and you end up with an unbalanced, unfocused, and slow website. These factors weren’t as big of a problem 5 years ago when mobile hadn’t really taken off yet, but as good as mobile devices are getting and as fast as wireless networks are getting, most sites still aren’t designed very well for mobile despite being responsive.

    It’s a problem to be sure, but it’s also an opportunity in disguise for forward thinking organizations that can prioritize speed and stand out from the crowd. This is a big opportunity that many developer focused companies can blow away their competition on.


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