Vviewpoints

I L L U S T R A T I O N S B Y A L I C I A K U B I S T A / A N D R I J B O R Y S A S S O C I A T E S

DOI: 10.1145/2633041

Viewpoint
Slow Search

Seeking to enrich the search experience by allowing for extra time and alternate resources.

words.” The resulting fast, word-orient-ed matching ignores the rich semantics of text but is an efficient way to capture some aspects of the similarity between queries and documents. Time-saving mechanisms such as search-result caching and index tiering are also heavily exploited, despite the risk that such approaches may cause relevant content to be missed.

Not All Searches Need to Be Fast

Although searchers have grown ac-
customed to rapid responses to their
queries, recent advances in our under-
standing of how people search suggest
there are scenarios where a search en-
gine could take significantly longer
than a fraction of a second to return rel-
evant content. 12 While someone search-
Building on these movements we pro-
pose the concept of slow search, where
search engines use additional time to
provide a higher quality search expe-
rience than is possible given conven-
tional time constraints.

Speed, Speed, Speed

Substantial research and engineering effort has been devoted to achieving low latency in large, complex computing systems such as search engines. 6 Search engines target speed for good reason. Research suggests that people perceive results that are delivered quickly as higher quality and more engaging than those delivered more slowly. Online experiments where server-side delays are injected into the delivery of search results have shown negative impact on people’s search behavior. 11, 12 For example, Google reported that intentionally increasing the load time of their search result page by as little as 100 milliseconds decreased the number of searches per person.

Further, these differences increased
over time and persisted even after the
delays were removed. In similar experi-
ments, Bing observed that artificial de-
lays lead to a decrease in the number
of queries and clicks, and an increase
in time to click. Even improvements
that seem like they should positively
impact the searcher experience have
been shown to have negative outcomes
if they increase latency. For example,
when Google experimented with re-
turning 30 results instead of 10, they
found that the number of searches and
revenue dropped significantly because
the additional results took a half-sec-
ond longer to load. 10

To achieve near-instantaneous speed, search engines make a number of compromises. They limit the complexity of the features and models used to identify relevant documents by, for example, making simplistic assumptions about language, often treating text as an unordered “bag of