Performance Is Good for Brains [We Love Speed 2024]

User experience and web performance are among the best indicators of online business outcomes. Faster websites have happier users. Those happy users visit longer and spend more. But why is that?

When we think about web performance, it’s easy to fall into an abyss of metrics. Backend time, Start Render, Core Web Vitals, Lighthouse scores… these metrics are useful and necessary, but they’re just a means to an end: Understanding how to create faster, more joyous user experiences.

In this talk, we walk through a brief history of UX and web performance research, highlighting key studies that connect the dots between performance and user experience and sharing some educated guesses about new metrics that are just around the corner.

You’ll take away insights into why slow sites enrage you, and why you should prioritize making your own sites and apps as fast as possible for your own users.

We still have so much to learn. Some day we’ll laugh at how much we assumed and how little we actually knew. But if we stay on course, we’ll get there.

Transcript

1. 1 Performance is Good for Brains webperf.social/@tammy @tameverts
3. Alarm Vectors by Vecteezy
6. Made pages 1.9 seconds faster, increased conversion rate by 94% 1-second improvement, 14% decrease in bounce rate and 13% increase in conversions Improved Largest Contentful Paint by 31%, increased sales by 8% WPOstats.com
10. Waiting is hard
11. Passive waiting is harder
12. Perception is more important than reality
13. Perception is more important than reality
14. How do we perceive time?
17. Our memory exaggerates wait times
19. We remember endings more than beginnings and middles
21. Time feels slower when we are relaxed
22. When the span between heartbeats is longer, time feels slower* *by milliseconds
23. Women tend to underestimate prospective time estimations compared to men. This suggests they may perceive time to be passing by more slowly.
24. Women tend to underestimate prospective time estimations compared to men.
25. Women tend to underestimate prospective time estimations compared to men. This suggests they may perceive time to be passing by more slowly.
26. Have you ever thought time is speeding up as you get older?
27. Have you ever thought time is speeding up as you get older? It is.
28. Over time, the rate at which we process visual information slows down.
29. Over time, the rate at which we process visual information slows down. This is what makes time ‘speed up’ as we grow older.
30. Users aged 65+ are 43% slower at using websites than users aged 21-55 nngroup.com/articles/usability-for-senior-citizens/
31. Our perception is affected by how time is quantified
32. 86,400 seconds
33. 86,400 seconds 1,440 minutes
34. 86,400 seconds 1,440 minutes 24 hours
35. 86,400 seconds 1,440 minutes 24 hours 1 day
39. 35 minutes 7 Sharonas
40. sex age pain heart rate boredom
42. How does memory work?
46. What is “flow”?
47. “…a state in which people are so involved in an activity that nothing else seems to matter; the experience is so enjoyable that people will continue to do it even at great cost, for the sheer sake of doing it” Mihály Csíkszentmihályi Flow: The Psychology of Optimal Experience (1990)
50. 50 Image by BalashMirzabey on Freepik It can take up to 23 minutes to regain focus after an interruption
51. 51 Productivity It can take up to 23 minutes to regain focus after an interruption
52. 52 Productivity Wellbeing It can take up to 23 minutes to regain focus after an interruption
53. Slow sites create extra friction in an already friction-filled world
54. The average web user believes they waste two days a year waiting for pages to load
55. What we say we want vs. what we need 1999 • 8 seconds 2006 • 4 seconds Now • 2 seconds
56. A wait longer than 2 seconds breaks concentration and affects productivity Robert Miller Response Time in Man-Computer Conversational Transactions
57. A wait longer than 2 seconds breaks concentration and affects productivity Robert Miller Response Time in Man-Computer Conversational Transactions 1968
58. 58 “We want you to be able to flick from one page to another as quickly as you can flick a page on a book. So, we’re really aiming very, very high here… at something like 100 milliseconds.” Urs Hölzle SVP Engineering, Google
60. What do we know about how people perceive speed on the web?
61. 61 Jakob Nielsen, Website Response Times
62. 62 When do we start to interact with a page?
63. 63 Jakob Nielsen, Website Response Times
65. “web stress” When apps or sites are slow, we concentrate up to 50% harder to stay on task
67. People experience slowness in the moment
68. Frustration peaks between 11.5 and 26% during browsing and checkout
69. Slowness affects perception of everything
70. fast slow
71. Content “boring” Visual design “tacky” “confusing” Usability “frustrating” “hard-to-navigate”
72. Slowness affects long-term behaviour
74. What we think we want does not always make us happy
79. “When, as with the Progressive JPEG method, image rendition is a two-stage process in which an initially coarse image snaps into sharp focus, cognitive fluency is inhibited and the brain has to work slightly harder to make sense of what is being displayed.” Dr. David Lewis Chair, Mindlab International
82. Slowness is a feeling, not a thought
83. “Phone rage”: How people react to slow mobile sites Tealeaf/Harris Interactive
85. nicj.net/measuring-continuity/
86. nicj.net/measuring-continuity/
87. Steve Souders Author, High Performance Web Sites “The real thing we are after is to create a user experience that people love and they feel is fast…
88. …and so we might be front-end engineers, we might be devs, we might be ops, but what we really are is perception brokers.” Steve Souders Author, High Performance Web Sites “The real thing we are after is to create a user experience that people love and they feel is fast…
89. How do you measure perception …at scale?
90. Biggest measurement mistakes 1. Not measuring at all You can’t fix what you don’t measure.
91. Biggest measurement mistakes 1. Not measuring at all You can’t fix what you don’t measure. 2. Assuming your experience is universal “It’s fast enough on my desktop/phone.”
92. Biggest measurement mistakes 1. Not measuring at all You can’t fix what you don’t measure. 2. Assuming your experience is universal “It’s fast enough on my desktop/phone.” 3. Not monitoring continuously Things can change suddenly (e.g., server issues, third parties).
93. Biggest measurement mistakes 1. Not measuring at all You can’t fix what you don’t measure. 2. Assuming your experience is universal “It’s fast enough on my desktop/phone.” 3. Not monitoring continuously Things can change suddenly (e.g., server issues, third parties). 4. Not monitoring real users Synthetic measurements are only snapshots. CrUX data is not comprehensive RUM.
94. Biggest measurement mistakes 1. Not measuring at all You can’t fix what you don’t measure. 2. Assuming your experience is universal “It’s fast enough on my desktop/phone.” 3. Not monitoring continuously Things can change suddenly (e.g., server issues, third parties). 4. Not monitoring real users Synthetic measurements are only snapshots. CrUX data is not comprehensive RUM.. 5. Not focusing on the right metrics e.g., “Load time” is dated; Core Web Vitals are only available in Chromium browsers.
95. Biggest measurement mistakes 1. Not measuring at all You can’t fix what you don’t measure. 2. Assuming your experience is universal “It’s fast enough on my desktop/phone.” 3. Not monitoring continuously Things can change suddenly (e.g., server issues, third parties). 4. Not monitoring real users Synthetic measurements are only snapshots. CrUX data is not comprehensive RUM. 5. Not focusing on the right metrics e.g., “Load time” is dated; Core Web Vitals are only available in Chromium browsers. 6. Looking only at averages or medians Measure at 75th and 95th percentiles to understand the breadth of user experiences.
96. Optimize the entire experience 1. Eliminate confusion whenever possible Don Norman, Cofounder/emeritus, Nielsen Norman Group
97. Optimize the entire experience 1. Eliminate confusion whenever possible 2. Make the wait appropriate to the results Don Norman, Cofounder/emeritus, Nielsen Norman Group
98. Optimize the entire experience 1. Eliminate confusion whenever possible 2. Make the wait appropriate to the results 3. Meet or exceed expectations Don Norman, Cofounder/emeritus, Nielsen Norman Group
99. Optimize the entire experience 1. Eliminate confusion whenever possible 2. Make the wait appropriate to the results 3. Meet or exceed expectations 4. End strong Don Norman, Cofounder/emeritus, Nielsen Norman Group
100. Made pages 1.9 seconds faster, increased conversion rate by 94% 1-second improvement, 14% decrease in bounce rate and 13% increase in conversions Improved Largest Contentful Paint by 31%, increased sales by 8% WPOstats.com
101. 101 Create an experience that isn’t just tolerable...
102. 102 Create an experience that isn’t just tolerable... it’s delightful
103. Thank you! webperf.social/@tammy @tameverts
104. The Psychology of Site Speed and User Happiness speedcurve.com/web-performance-guide/the-psychology-of-web-performance/ Why Waiting Is Torture nytimes.com/2012/08/19/opinion/sunday/why-waiting-in-line-is-torture.html Wrinkles in Subsecond Time Perception Are Synchronized to the Heart onlinelibrary.wiley.com/doi/abs/10.1111/psyp.14270 Sex Differences in Time Perception During Self-paced Running ncbi.nlm.nih.gov/pmc/articles/PMC5065319/ Why the Days Seem Shorter as We Get Older cambridge.org/core/journals/european-review/article/why-the-days-seem-shorter-as-we-get-older/ Flow: The Psychology of Optimal Experience Mihaly Csikszentmihalyi The Cost of Interrupted Work: More Speed and Stress ics.uci.edu/~gmark/chi08-mark.pdf Response Time in Man-Computer Conversational Transactions dl.acm.org/doi/10.1145/1476589.1476628 Website Response Times nngroup.com/articles/website-response-times/ Progressive Image Rendering: Good or Evil? radware.com/blog/applicationdelivery/wpo/2014/09/progressive-image-rendering-good-evil/ The Psychology of Waiting Lines Don Norman – jnd.org/the-psychology-of-waiting-lines/ Sources