This just in: Applications that are mere gimmicks — think Lighter, iFart and IQ Test — lose the attention of smartphone owners after being just used a few times.

Flurry Inc., a San Francisco-based startup that tracks the apps marketplace, recently conducted a study of more than 1,800 apps, 75 million consumers and four mobile platforms: iPhone, BlackBerry, Android and JavaME. The goal was to determine user retention rates across multiple categories over a 90-day period and to see if consumers returned to use a downloaded application within subsequent periods lasting 30, 60 and 90 days. It found that:

• News & reference apps are used the most — more than once a day at a rate of 11 times per week.
• Social networking apps are used six times a week.
• Health and fitness apps are used 7 times a week.
• Games are used 7.4 times a week.
• Book-related apps are used 10 times a week. (Which to me means it’s only a matter of time before Apple tries to turn the iPod touch/iPhone into e-book readers)