Gestalt theory and Geons

Two of the theories that we have been discussing regarding object recognition are the gestalt theory and geometrical ions, called geons. I have heard of both of these theories before, and both have always struck me as overly simplistic. We are able to identify by sight countless objects that we encounter in our everyday lives. Even in the absence of color and markings that might give us additional clues to an objects identity, we are able to quickly identify so many objects, of such varying shapes, that I find it hard to believe that either of these views accurately describes the incredibly complex processes that our visual brain must go through in order to properly identify objects.

The geon theory is the less plausible of the two for me. The world we see is made up of so many objects, of such varying shape and complexity that I find it difficult to believe that it can really be broken down into a number of goens, that can be distorted to form any object that we see. Obviously the world is made up of different shapes, and certain objects like a phone, mug or briefcase like we looked at in class can be broken down into only a few geons, but in order for the theory to be relevant, the world would have to break down into a reasonable number of geons. This is where the theory breaks down for me. Considering the complexity of the objects in the world, I cannot imagine that anything less than several million geons would be able to cover every object that we are able to identify, and with so many, the point of the theory, that the world is easily classifiable, is gone.

The Gestalt theory makes more sense to me, but even it makes the process of object recognition seem too simple. The Gestalt theory says that objects are grouped by proximity, similarity, closure, good continuation, and common fate. This makes sense to me because when we see a complex scene, we are able to see most things as different objects, or belonging to a group, like different people walking in a crowd, or a flock of birds flying through the sky. I think that especially with regards to good continuation and common fate the Gestalt principles make some very good points about our object recognition systems, however, even though I think the theory makes some good points, and makes much more sense than the geon theory, I still think that the gestalt theory is too simple. I have a hard time going from identifying a general object in a certain area to being able to identify your cousin in a picture of his third grade class.

All in all I think that both of the theories have pros and cons associated with them. While I do not have a better suggestion than either of these for how we are able to recognize and identify objects, I think that other theories, perhaps incorporating aspects of both, would give a better general description of how our visual system works.

March 30, 2008

bionic eyes and cochlear implants

At the beginning of chapter 3, the text book says that in order to appreciate the complexity of the eye, you should try to build a bionic one. Obviously this would be an incredibly challenging thing to do, but how much more complicated would it be to design a bionic eye than a cochlear implant? Obviously I am thinking about these two devices in a conceptual way, as I have no engineering background and no idea of how complicated the mechanics of what I am talking about would be, but that being said, I an surprised that bionic eyes have not become as advanced or common as cochlear implants are.

The reason that I am surprised, is because I don’t see how the two would really be that different. Cochlear implants transform sound waves into electrical impulses, which the brain can interpret as noises. Why would a bionic eye be able to do the same for the energy waves that we interpret as light and color? A video camera is able to transform light entering the lens into electronic signals, that are able the be interpreted and either recorded to a tape, or projected onto the camera’s lcd screen. I do not see why a bionic eye would not be able to transmit the electrical signals that a video camera can produce via specifically placed electrodes to the vision centers of the brain. Obviously the visual system in a human being is incredibly complicated, and the science involved in actually placing the electrodes into the brain would be phenomenally complex, but after our study of the auditory system, I’m not convinced that the electrodes in cochlear implants are much less intricately placed. However, despite the seemingly similar conceptual aspects of bionic eyes and cochlear implants, cochlear implants seem to be far easier to make and implement into patients than bionic eyes are. What makes the electrode design and placement so much more difficult in the visual system that bionic eyes are years behind of the advances that have been made in cochlear implants? As we continue to study the brain systems involved in vision, I will be interested to see if there is anything about the location of these systems, or the mapping of theses brain areas that would make the placement of the electrodes so hard, it would account for the difficulty of construction of bionic eyes, or if it is something else about the device itself that makes them so much harder to make than cochlear implants.

Sunday, March 23

Color Vision

As we enter our section on vision, I find myself again considering what exactly color vision is. Several years ago, one of my friends offered a view on color vision that still botheres me to this day: how do I know that the color I see as blue is the same color that everyone else sees as blue? Obviously when someone asks me what color the sky is, I do not say it is purplr, or orange, but what if another person were able to view the world through my eyes, and actually did see the world in different colors than what they were used to. I don’t know if this will make much sense to anyone else, or if I am describing the question well, but the core of the question essentially comes down to what is a colo