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A Study of the Effect of Thumb Sizes on Mobile Phone Texting Satisfaction

Vimala Balakrishnan and Paul, H.P. Yeow

Journal of Usability Studies, Volume 3, Issue 3, May 2008, pp. 118-128

Article Contents


Text messaging or texting is the common term for sending short (maximum of 160 characters and spaces) text messages using the Short Message Service (SMS) from mobile phones. The individual messages are called text messages and more colloquially SMS. Text messaging has been a tremendous success in many countries, including Asian countries like Singapore, Philippines, and Malaysia. Malaysians, for example, were found to have sent 11.7 billion messages in the first three months of 2007, compared to only 7.4 billion in 2006 (The Star, 2007). Texting is a quick, easy, and cheap way to communicate with anyone, anywhere, and at anytime.

The popularity of SMS has heightened the interest in mobile phone research. A lot of studies have occurred on the use of mobile phones and the SMS in certain countries (Faulkner and Culwin, 2005; H?flich and R?ssler, 2002; Ling, 2005). Social and psychological effects of SMS were also studied to examine the underlying motivations of using SMS (Reid and Reid, 2004). Some researchers have done usability studies of mobile phones (Balakrishnan et al., 2005; Soriano et al., 2005) and some have compared the performance of the text entry methods (Friedman et al., 2001; James and Reischel, 2001). Although numerous studies have been conducted related to SMS, very few studies were related to SMS users' subjective satisfaction (Han et al., 2004; Ling et al., 2007; Yun et al., 2003).

User satisfaction is a main priority for many product designers. For example, in Japan, product designers employ Kansei engineering techniques to design products (such as cars, houses, and costumes) considering the end user's perceived desirable features. (Kashiwagi et al., 1994; Miyazaki et al., 1993; Nagamachi, 2002). Mobile phone designers considered user satisfaction when evaluating the look-and-feel of mobile phone. (Yun et al., 2003). The success or failure of any product is heavily dependent on the end users' satisfaction. Literature reviews revealed that no studies investigated the effect of users' varying thumb sizes on texting satisfaction. Some users with large fingers have commented about the difficulty of using mobile phones to send text messages (Axup et al., 2005; Faulkner and Culwin, 2005; Soriano et al., 2005); however, the researchers did not take any finger measurements into consideration.

Studies related to keypad designs are numerous; however, most studies attempt to tackle keypad design problems by focusing on the text input mechanism (Mackenzie, 2002; Silfverberg et al., 2000). The Fastap keypad was designed by placing 52 independent keys onto an area the same size as the standard ISO keypad. Though the Fastap keypad offers an increased performance over an ISO keypad, it remains to be seen how mobile phone users will assess the trade-off between the increased performance of advanced input technologies and the additional cost (Cockburn and Siresena, 2003). Several studies identified tiny key sizes as one of the problems related to mobile phone use (Kurniawan et al., 2006; Soriano et al., 2005). A study conducted with a group of older people revealed that keys placed too close to one another cause problems while handling a mobile phone (Ornella and Stephanie, 2006). Though many studies identified potential problems related to keypads, no study took any physical measurements of the thumbs or fingers into consideration.

This study focuses on keypad design factors to investigate and to evaluate how mobile phone users' thumb size affect their text messaging experience.

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