They say a first impression is everything. A first impression typically consists of what, a five second interaction, that is primarily a visual one. So really a first impression is a first glance, or sight. Its all very cliche, and yet with every cliche there is some truth.
I work with people that are no longer of sound mind, or body. It is interesting to have to communicate with those who are no longer able to string together a coherent thought, let alone any need or want. So how do they. It based on a look. A little look. Saying I am in pain, I am thirsty, I am happy and at peace. Most people are never trained, or study these few expressions but guarentee that most could identify them. These interactions consist of maybe no more then five seconds. From those five seconds a course of action is decided upon.