The human machine interface (HMI) is a main communication method between human and computer. Through current HMI, a machine receives and accurately responds to the commands instructed by the users. In the next generation of HMI, machines will be required to deal with more challenging problems/decisions (such as affective evaluations, ethical quandaries, and other innovations) in a self-governing manner. Thus, future HMI should be able to provide information about users' emotion to the machine for affective evaluation. In this paper, we focus on the natural connection method that can improve machines in making the acquaintance of the users. However, connecting sensors scattered on the human body poses serious problems concerning comfort and convenience. Therefore, the authors introduce the Intra Body Communication (IBC) for connecting various physiological sensors on the human body such that the physiological information can enrich the capability of the computer in cognition of the user's emotion. In addition, the authors also reported two pilot studies: using the IBC for connecting the physiological sensor on the human body and using the physiological parameters to estimate the degree of fatigue of the user. © 2012 IEEE.