Psychology of Performance

Average rating: ***..
(3.40, 48 ratings)

Topics of discussion:

  • Relativity of time
  • Mind hacks and perception
  • The state of flow
  • Considering the user expectations (competition, page purpose)
  • User-onload time
  • Providing feedback to the user
  • Using transitions
  • Progressive rendering
  • How long is a blink of an eye
  • Color and speed
  • Clutter
Photo of Stoyan Stefanov

Stoyan Stefanov


Stoyan Stefanov (, @stoyanstefanov) is a front-end engineer at Yahoo! Search. Creator of the online image optimization tool and architect of YSlow 2.0. Book author (Object-Oriented JavaScript) and contributor (Even Faster Web Sites, High-Performance JavaScript) and speaker (Velocity, Ajax Experience, JSConf).

Comments on this page are now closed.


Picture of Steve Souders
Steve Souders
05/17/2010 5:28am PDT

At my very first meeting to discuss web performance back in 2004, one of the attendees pointed out that the goal wasn’t to optimize some time measurement, but it was really to optimize the user perception of web site speed. We often lose sight of this point in our focus on implementation and milliseconds. I love metrics and dashboards, but it’s what our users feel when they use our sites that really matters. Stoyan is a leader in the web performance community, focusing on image optimization, JavaScript, and more. I’m looking forward to hearing him come at performance from the perspective of user perception.

For Velocity China sponsorship information for companies outside China, contact Yvonne Romaine at

  • Google
  • Strangeloop
  • Yahoo! Inc.
  • Dyn Inc.
  • Facebook
  • Schooner Information Technology
  • Tilera
  • AlertSite
  • AppDynamics
  • Aptimize
  • CDNetworks
  • Circonus
  • Cloudscaling
  • Clustrix
  • Coradiant
  • Dell
  • DTO Solutions
  • MaxiScale
  • Neustar
  • Nokia
  • NorthScale, Inc.
  • Shopzilla
  • Splunk
  • Virident
  • Zoompf
  • Neustar

For information on exhibition and sponsorship opportunities at the conference, contact Yvonne Romaine at

Download the Velocity Sponsor/Exhibitor Prospectus

Download the Media & Promotional Partner Brochure (PDF) for information on trade opportunities with O'Reilly conferences or contact mediapartners@

For media-related inquiries, contact Maureen Jennings at

To stay abreast of conference news and to receive email notification when registration opens, please sign up for the Velocity Conference bulletin (login required)

View a complete list of Velocity contacts