Multifunctioning systems are being used extensively in households nowadays. System information is summarized on a portable terminal. Users benefit from the value produced by multifunctional systems. It is conceivable that the motivation to use such systems can increase or decrease depending upon the balance between the amounts of information on the terminal screen and system information. The ability to create a model capable of showing the ranges of various amounts of information that increase users’ willingness to use a system is extremely useful. Thus, to motivate the elderly, we explore the relationship between these amounts (information on a terminal screen and system information). We create a smartphone application that can control the amount of information, and the participants perform a task in which varying amounts of information are combined. Thus, we could discern the participants’ willingness to use the system and create a model to derive optimal amounts of information.