How do we know what we really see?

Having viewed Psycho for the second time this evening, I took a very long, nervous bath in lieu of a shower. Aside from the obvious reasons, it just seemed to me that this time the infamous shower scene was much more terrifying than I had ever remembered it to be. Being the good little procrastinator that I am, I forwent doing any actual work and consulted my resources to find all that I could regarding this scene. Gathering what I could from various sources (mostly Wikipedia) I discovered that the scene is comprised of around 71 angles and 50 cuts, (which is a hell of a lot for a three minute scene) and the "Soviet Montage" style in which it was shot contributes to the hasty, psychotically horrifying tone. I also discovered that there are only three frames of actual penetration (knife to skin, that is), which adds up to about an eighth of a second in that stretch of time. So little, in fact, that it would only register subliminally.  

That made me think (of course) about how much we really see. The three frames of stabbing must have been noticed by my brain, and added to my irrational paranoia this evening, but I had no awareness to them. Much research has been done concerning how effective subliminal messages are, ranging the gamut from a lot to nothing, but in any event it does make you wonder how much of our emotions and actions are dictated by things we never consciously see or hear. It must happen, to some degree, because a lot of the things we are told or shown influence us to do certain things, even if we don't connect the two right away. I believe I am going to be a little less impulsive as the days go by, especially in these important times. Before I do something, I'll pose the questions "Why am I doing this?" or "How will this affect me in the long run?" or "Are these actions really my own?". 

It's a frightening prospect to believe that what we do does not come from ourselves.