Mobile phones provide the freedom to participate in a variety of communication styles, ranging from simple voice-based communications to advanced text-messaging services. The decision to perform complex usage activities is determined by the interrelations of three personality traits. Using the optimum stimulation framework, the study hypothesizes that personal innovativeness and individual playfulness increase an individual's optimum stimulation level (OSL). Survey data from 246 text-messaging users showed that personal innovativeness, playful personality, and OSL can predict complex mobile usage patterns. Future research can append personality traits to existing IT adoption frameworks. Practitioners can incorporate their conclusions from the personality traits into device designs and applications while enhancing the widespread use of m-commerce and entertainment services.KEY WORDS AND PHRASES: Consumer behavior, exploratory behavior, mobile commerce, optimum stimulation level, personal innovativeness, playfulness, SMS, structural equation modeling usage, text messaging.Mobile phones have provided us with the freedom to participate in a variety of communication styles, from simple voice-based communications to numerous data-based applications. With the different data contents they support, mobile phones have fulfilled most, if not all, of our basic communication needs. The ability to remain in touch with anyone anywhere is merely a few button clicks away. Inexpensive subscription fees have generated a huge consumer base that continues to grow exponentially. According to the International Association for the Wireless Telecommunications Industry (CTIA), the number of wireless subscribers in the United States is 219 million, with wireless use exceeding 850 billion minutes as of June 2006 (www.ctia.org/research_statistics/index. cfm). Mobile phones are now essential for keeping in touch with friends and family as well for functioning in the business domain.Advances in information and telecommunication technology also allow mobile users to participate asynchronously through various messaging services. Enhanced subscription services (e.g., text messaging, e-mail, Internet access) are redefining innovative mobile applications. One of the most popular mobile applications is Short Message Service (SMS, "text messaging," or "text messages"). "SMS allows text messages to be sent between mobile phones and other devices" [26, p. 317]. According to recent data compiled by SMS.ac, the volume of SMS exceeds 5 billion text messages per month in the United States and will account for 68 percent of data revenues by 2010. Currently, voice services dominate 90 percent of worldwide mobile services, while almost 9 percent of non-voice revenues come from text messages [91]. M:Metrics, Inc. indicates that 38 percent of U.S. mobile phone users (or 72 million subscribers) engage Downloaded by [FU Berlin] at 20:36 30 June 2015 8 PRUTHIKRAI MAHATANANKOON in text messaging [78]. The popularity of text-messaging activities deserves serious res...