"Perception (from the Latin perceptio, percipio) is the process of attaining awareness or understanding of the environment by organizing and interpreting sensory information. All perception involves signals in the nervous system, which in turn result from physical stimulation of the sense organs. Perception is not the passive receipt of these signals, but can be shaped by learning, memory and expectation. Perception involves these "top-down" effects as well as the "bottom-up" process of processing sensory input. Perception depends on complex functions of the nervous system, but subjectively seems mostly effortless because this processing happens outside conscious awareness."
It is interesting that the biggest hurdle in changing our perception of things lies in the fact that we are often unaware of what influences it in the first place. As explained above, perception occurs outside conscious thought yet it can be changed through training and experience. Our perception is the product of years of development in the physical, mental and emotional levels of our being; it is affected by our environment, both physical and social; the people who we interact with; our schooling and religion or lack thereof. Some of these things we might have some actual knowledge of their origin; some have deep relations with our childhood that we have forgotten yet a sole memory surfaces ever slightly, making us wonder where it came from and why does it make us feel in such a way.
If we are not cognizant of what makes the nuts and bolts of our perception, how can we change it to our benefit? This is a tough endeavor, especially since many of the things that make our view of what the world is and what happens in it are rooted in our ego (never mind Star Trek, the ego is the final frontier and the toughest one to overcome). As such, we might think we want them changed, while inside we scream to be left alone. No scarier thing to face than the death of the self... But back to the problem at hand, recognizing gaps in our perception and how to bridge them somehow.
Ronald B. Adler on his book Looking Out, Looking In states there are four steps used in matching meaning with our experiences: selection, organization, interpretation and negotiation. Selection deals with what stimuli we choose to pay attention to or ignore; organization entails arranging these in some way we can use; interpretation of our perceptions to make use of the stimuli received; and negotiation which involves our interactions with others and their own perceptions. Many variables can have profound influence on any of these.
Applied to the study of martial arts, now that we have compartmentalized the makings of our perception it might be easier to identify areas where our previous knowledge and experience is lacking. For example, let's look at selection: how do we discern a true attack from a feint, which techniques work for us personally, etc. What about interpretation? Understanding and properly recognizing precursors of violence are largely based on our training and experience (or lack thereof). Many steps of the development of perception correlate and fluidly evolve and change, like being kicked in the face in sparring (stimuli) can make someone ignore previous training (selection) therefore breaking down previously thought of and practiced responses (organization) and alter how that person continues the fight (negotiation). The process of effecting changes to our perception can be a result of long study and life experience, or something sudden and unexpected.
Awareness in battle
Breaking concrete is one of those "magical" karate skills
Zanshin, "remaining mind"
Perception... it is all pervasive yet we go through life mostly oblivious to its grip on what we do, think and feel. Let us not forget that during our waking moments anything could bring about a momentous change in how we perceive ourselves, others and the world around us, be it through providence or our own efforts.