The Effects of Bold Text on Visual Search: The Downside of Highlighting
http://www.webusability.com/usability_article_Effect_of Bold_on_Search2003.htm

Bailey, Robert
Web Usability
2003

Abstract:

Everybody knows that by making a word bold that it will ‘standout,’ be perceived more readily and (obviously) processed faster. For example, which of the following formats will elicit the fastest performance by customer service representatives -- A or B?