The above link is to a short video clip I took during my stay in Alaska. To me this is the perfect example of bottom up and top down processing. Why you ask? I will begin with the story of the event that took place.
Over the summer I went on a beautiful cruise to Alaska where I was able to see magnificent sights. Some of these sights were specifically amazing because I had only ever seen them on tv or in the movies. One evening during dinner with my friend, we noticed a strange white mist approaching the ship. We stopped in our tracks because for a minute it looked like a large white form was penetrating a mountain. We knew that what we thought we were seeing was impossible so we left the dining hall and took to the top of the ship for a closer look. To our amazement the approaching white mass began to take several different shapes and even seemed to be floating and changing color. We began to go crazy because we thought we were witnessing some kind of extraordinary phenomena. We then took turns exchanging different ideas of what we thought the strange mass could be, but all of our conclusions were illogical or just plain crazy. About an hour later we were INSIDE of the strange white floating material, it was until then that we realized it was just a very thick layer of fog floating over a landmass. Even upon figuring out the puzzle we still were amazed by the sight and the works of mother nature.
Bottom up processing starts with information received by the receptors, but what if the information you see is new and hence unidentifiable? Thats when top down processing can come into play since it relies on knowledge or the expectations of the individual. In our case our knowledge of floating white masses was very limited, of course fog and mist came into play but it was like no fog we have ever seen. Maybe someone who studied in meteorology or hydrology would of had a much easier time deciphering the approaching mass but that just goes to show that perception is different for everyone. Imagine how different that white mass would look to 100 different people who carried their own array of knowledge and expectations. Each individual would probably witness something entirely different.
Thats the beauty of perception, I suppose that Helmholtz had the same idea as I, when he introduced his theory of unconscious inference. Our ability to create perceptions from stimulus information that can be seen in more then one way is a wonder but it makes sense. Take for example the infamous blue/black dress that was floating around the internet, how is it possible that something as constant as color is perceived differently by people around the world? The best thing I believe we can do is refer to the Gestalt laws of organization. Though they are heuristics, they help explain why our perception changes and varies depending on our culture, knowledge, and background. A study that shows how the Gestalt laws influence our perception was “the hollow face experiment” done by Gregory (2007). The participants reconstructed a face on the hollow back of a mask. The subjects perceived that there was a protruding nose even though there was not, because of our assumptions. That is just one of the many studies done throughout history that supports just how much our perception is based on more than what meets the eye.
Gregory R L, 1997 “Knowledge in perception and illusion” Philosophical Transactions of the Royal Society of London, Series B 352 1121 ^ 1128
“Cognitive Psychology” Goldstein (2011)