Surfers Judge Web Pages Seen for Only 50ms?

Does your Web site load quickly? A study conducted by Gitte Lindgaard at Carleton University in Ottawa claims that Web surfers can make up their minds about pages they see for as little as 50ms, and that those snap judgments are confirmed when users spend more time examining the content of a site.

In the study, published in the journal Behavior and Information Technology (a summary is available at, volunteers were shown images of Web pages for as little as 50ms (one twentieth of a second) and asked to rate the pages’ visual appeal. The participants were then asked to re-evaluate the same pages after scrutinizing them for a longer period of time. The study found that the participants’ snap judgments lined up well with the more detailed examinations: opinions formed on seeing the page for just 50ms were very similar to their opinions after a more-measured read.

Although the study’s methodology isn’t clear from the summary, it likely doesn’t conclude that Web surfers make decisions about Web pages in as little as 50ms, but rather that they can make decisions about things they’ve seen for as little as 50ms. Even the best human response times (e.g., folks like musicians and athletes responding to anticipated events) are rarely below 100ms, so it’s doubtful study participants both responded to and evaluated the pages in 50ms. The eye can certainly perceive an image in 50ms, but the brain retains an after-image of the visual stimuli and can process and evaluate that image for quite some time after the original visual stimuli is gone. (The after-image, or persistence of vision, is the reason television and film images appear to move in lifelike ways, when really they’re just a series of static pictures.)

The consistency of participants’ snap judgments and more-detailed examinations of pages may be attributable to a “halo effect,” where an appealing, attractive design may make users more inclined to regard the rest of the page positively, where an unappealing design may cast a negative pall on even the most engaging and relevant content. People enjoy being right, and tend to look for things which reinforce their first impressions before admitting their impression may have been wrong.

Regardless of the time involved, immediate perceptions undoubtedly count. “Unless the first impression is favorable, visitors will be out of your site before they even know that you might be offering more than your competitors,” Lindgaard warns.