CHI 2003: NEW HORIZONS

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Talk: Trust,SpecializedSecurity
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Prominence-Interpretation Theory:
Explaining How People Assess Credibility Online
BJ Fogg
Stanford Persuasive Technology Lab
CSLI, Stanford University
Stanford, CA 94309 USA
bjfogg@stanford.edu
ABSTRACTWHAT IS PROMINENCE-INTERPRETATION THEORY?

Four years of research has led to a theory that describes how
people assess the credibility of Web sites. This theory
proposes that users notice and interpret various Web siteelements to arrive at an overall credibility assessment.
Although preliminary, this theory explains previous research
results and suggests directions for future studies.

Prominence-Interpretation Theory posits that two things
happen when people assess credibility online (see Figure 1):

Keywords

Online credibility, user trust, HCI theory, Web site design,
involvement, cultural differences, Web credibility.
INTRODUCTION

The success of most Web sites today depends on whether
users perceive the site to be credible. If users think a site
lacks credibility—that the information and services cannot
be trusted—they will abandon the site and seek to fill theirneeds in other ways. Because fraud and low-quality
information is perceived to be a growing problem in theonline world [5], creating a usable Web site is no longer
sufficient. HCI professionals must design Web sites for
credibility as well. A key step in this process is to develop a
principled understanding—i.e., a relevant theory, informedby quantitative research—of how people assess thecredibility of online content.
This short paper presents a theory about online credibility
evaluations: Prominence-Interpretation Theory. Although
this theory is new and the concepts are preliminary, the early
responses and critiques have been positive and constructive.
In four early presentations of this work (three at Stanford
University and one at the U.S. National Cancer Institute)academics and HCI professionals have found value in thetheory. The time has come to share ProminenceInterpretation Theory with a wider audience to generate
additional feedback and critiques that will ultimately
improve our HCI community’s collective understanding
about how users assess credibility online
ORIGIN OF PROMINENCE-INTERPRETATION THEORY

Prominence-Interpretation Theory grew out of four years ofquantitative research on Web credibility by Stanford’s
Persuasive Technology Lab [1]. The research included over
6,500 participants in a variety of studies. This theory alsodraws on the results of related research by other groups, bothacademic and industrial [1].

Copyright is held by the author/owner(s).
CHI 2003, April 5–10, 2003, Ft. Lauderdale, Florida, USA.
ACM 1-58113-630-7/03/0004.

1. The user notices something (Prominence), and
2. The user makes a judgment about it (Interpretation).

If one or the other does not happen, then there is nocredibility assessment. The process of noticing a prominentelement and making an interpretation happens more thanonce when a person evaluates a Web site, with new aspectsof the site being noticed and interpreted as the user makes anoverall assessment of credibility.
Prominence-Interpretation Theory may seem apparent –organized common sense. However, one could argue thatmuch like an answer to a riddle, this theory seems obvious
only after it is revealed.
Prominence Explained

The first component in the theory is Prominence. In thiscontext “Prominence” is the likelihood that a Web siteelement will be noticed or perceived.
It stands to reason that before a Web site element can affect auser’s credibility assessment of the site, the user must first
notice the element. If the element is not noticed, it will haveno impact on the credibility assessment of the site. For
example, a user may not notice a Web site’s privacy policy.
As a result, the privacy policy will have no impact on how
the user assesses the credibility of the site. In contrast, otherelements on a Web site may be highly prominent. For
example, a large image of person in the center of a Web pageis likely to be noticed. This image will then play a role in thecredibility assessment of the site.
At least five factors affect Prominence:
1. Involvement of the user (i.e., the motivation and ability
to scrutinize Web site content) [3]2. Topic of the Web site (e.g., news, entertainment) [2]
3. Task of the user (e.g., seeking information, seeking
amusement, making a transaction) [6]4. Experience of the user (e.g., novice vs. expert in regard
to subject matter or Web conventions) [6]5. Individual differences (e.g., a person’s need forcognition, learning style, or literacy level)
The most dominant factor affecting Prominence may be user
involvement. When a user goes to a Web site with a highlevel of motivation (e.g., seeking an answer to a criticalhealth problem), he or she will notice more things about theWeb site. When user motivation and ability are both high [4]

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CHI 2003: NEW HORIZONS

Short Talks:
Talk: Trust,SpecializedSecurity
Section& Safety
Figure 1:
Core components in ProminenceInterpretation TheoryProminence

X Interpretation = Credibility Impact

An element’s likelihood ofbeing noticed whenpeople evaluate credibility.

more Web site elements will cross the cognitive threshold of
being unnoticed to being noticed.
In addition to the five factors listed previously, other factors
are likely to play a role in Prominence. Further research andanalysis will help illuminate how these factors affect theProminence component of this theory.
Interpretation Explained

The second component of the theory is Interpretation. In thiscontext “Interpretation” is a person’s judgment about anelement under examination. In other words, theInterpretation component is the user’s evaluation of a Website element, good or bad. For example, a user may interpreta broken link on a Web page as a sign that the site has been
neglected – or that the site was not carefully created in thefirst place. In either case, the broken link will contribute to alower credibility perception of the site.
Various factors affect Interpretation:
1. Assumptions in a user’s mind (i.e., culture, pastexperiences, heuristics, and so on) [2]2. Skill/knowledge of a user (e.g., user’s level ofcompetency in the site’s subject matter) [6]3. Context(e.g., the user’s environment, user
expectations, situational norms, and so on)
As the Interpretation component suggests, users do notinterpret identical Web site elements in the same way.
Culture plays a role in making these judgments. For example,a news Web site that has a passage from the Bible will affectpeople differently. Some people will interpret this Bible
verse positively and assign more credibility to the Web site;others will interpret the Bible passage negatively.
In addition to user culture and expectations, the context ofInterpretation matters – the user context, the task context,and more. For example, if a person is hurriedly looking forthe best airfares online while at work, she will likely interpretall popup ads negatively. However, if the same user isrelaxing at home and leisurely browsing travel sites forvacation ideas, a relevant popup ad might offer her welcome
information.
Future work can expand and refine understanding of thefactors that affect Interpretation.
Repeating the Process of Noticing and Evaluating

In most cases a user will quickly notice Web site elements
and evaluate them, usually an iterative and subconscious
process, all the while compiling an overall assessment aboutthe site’s credibility. People apparently repeat this process,focusing on different Web site elements, until they aresatisfied with their credibility conclusion or until otherconstraints stop them, such as a lack of time or skill.
A THEORY WITH EXPLANATORY & PREDICTIVE POWER

A good theory will have the power to explain past research
results and to predict profitable directions for future inquiry.
Prominence-Interpretation Theory does both. For example,
the theory explains a puzzling result from a study completedin 1999 [3]. This experiment showed that the more critical

What value or meaning
people assign to element,
good or bad.

The impact that element has on
credibility assessment.

the user’s information need, the greater the negative
credibility impact of typographical errors on a Web page.
Prominence-Interpretation
Theorycanprovide
aparsimonious explanation: Increased user involvement led toincreased prominence of the site’s typographical errors.
This theory also resolves what seemed to be a discrepancy inrecent research findings. A study in early 2002 suggested
that a site’s privacy policy was a key element in establishingcredibility [5]; in contrast, a later 2002 study showed thatprivacy policies had virtually no impact on credibility [2].
These findings can live together in harmony when viewed
from the perspective of Prominence-Interpretation Theory.
It’s now clear that the first study focused solely on
Interpretation. In the first study researchers called people on
the telephone and asked them to evaluate the impact a site’s
privacy policy would have on perceived credibility. In
contrast, the second study focused on Prominence. Study
participants visited actual Web sites to evaluate credibility.
In the second situation users almost never noticed a site’s
privacy policy. These two studies reached different
conclusions because they examined different components ofcredibility assessment.
Prominence-Interpretation Theory also has predictive value.
The theory suggests that future credibility studies could
profitably examine the role of user involvement, site topic,
user task, and so on. In addition, to better understand what
affects Interpretation, future research could examine (ormanipulate) user assumptions, knowledge, or context.
CONCLUSIONProminence-Interpretation Theory breaks new theoreticalground and creates a foundation for enhanced understandingof online credibility. Not only can this theory help HCI
researchers, but increased theoretical understanding can alsotranslate into practical insights that will benefit HCI
professionals who seek to design Web sites for credibility.
REFERENCES
1. A bibliography of research relating to online credibility is available at
http://credibility.stanford.edu/credlit.html.
2. Fogg, B.J., Soohoo, C., Danielsen, D., Marable, L., Stanford, J., &Tauber, E. (2002). How Do People Evaluate a Web Site’s Credibility?
Results from a Large Study. Published by Consumer WebWatch.
Available at http://credibility.stanford.edu/mostcredible.html.
3. Kim, N. (1999). World Wide Web Credibility: What Effects do
Advertisements and Typos Have on the Perceived Credibility of Web
Page Information? Senior Honors Thesis. Stanford University.
4. Petty, R.E. & Cacioppo, J.T. (1986). The elaboration likelihood model ofpersuasion. In L. Berkowitz (Ed) Advances in Experimental Social
Psychology, 19, New York: Academic Press, 123-205.
5. Princeton Survey Research Associates (2002). A Matter of Trust: What
Users Want From Web Sites. Results of a National Survey of Internet
Users for Consumer WebWatch. Available at
http://www.consumerwebwatch.org/news/ report1.pdf.
6. Stanford, J., Tauber, E., Fogg, B.J., Marable, L. (2002). Expert vs.
Online Consumers: A Comparative Credibility Study of Health andFinance Web Sites. Available at http://www.consumerwebwatch.org/
news/report3_credibilityresearch/slicedbread_abstract.htm.

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