I spent much of my research career trying to understand how the brain processes visual information - much of the stuff that you heard about in monsense, BV, and visual anatomy and physiology. Being in my current administrative position, I had to discontinue my research, and repress any urge to talk vision to my non-visual administrative colleagues. Every once in a while I slip and throw out visual factoid, and they just look at me esotropically - see I just can't say those things back at the office anymore.
Well, I now have an audience of new and practiced vision experts, so there is no hope for me to repress any urges to talk vision. But Dean Davis asked me to give a commencement speech and provide professional and personal advice to the optometry graduates. Well, I often want my cake and eat it too, so I am going to both talk vision and give advice in this commencement address. But I promise to do so and still comply with the cardinal rule of commencement speeches - end in ten minutes or less - and observe a prohibition by the optometry faculty and not talk about sea foam green.
This is how I will cut my cake. I will present five vision findings. For each, I will describe a facet about how the visual system operates, and then associate it with something that I have learned in my own career that I want to share with the graduates.
Vision Finding 1 - Vision is historical, or when we see something it has already happened. It takes about 80-100 msec to see something, depending on the complexity of the stimulus. Let me use a baseball example to illustrate the import of the historical nature of vision.
It takes about 0.3 of a sec for a 90 mph fast ball to leave the pitcher's hand and cross the plate. If it takes you 0.1 of sec to see the ball, then when you see the ball leave the pitcher's hand, it is already a third of the way to the plate. When you see the ball cross the plate, it is already in the catcher's mitt. If you wait to see the ball cross the plate you will never hit it. To hit the fastball, you have to anticipate where it will cross the plate once you see the ball leave the pitcher's hand.
Life will throw you plenty of fastballs, and seems that life's arm speed is only getting faster. You will need to anticipate and project the future if you are to get a hit. And beware of the curve ball
Vision Finding 2 - Our visual world is three dimensional. The perception of depth and distance is as basic and common as our perception of brightness, color, shape, or movement. However, the elementary nature of our 3D visual world is the result of a very complex construction. Since the retinal image is flat, any information about depth and distance must be derived from related information on the retina, such as cues associated with brightness changes (shadows), spatial relationships (interposition and relative size), and relative movement velocities. And the most amazing, our 3D perception is calculated from the very small differences in the relative position of similar stimuli across the retina of our two eyes, which gives rise to stereoscopic depth perception.
The origins of depth perception make me think about other things that I routinely encounter in my life that are as elementary and ubiquitous as the three dimensionality of our visual world. However, when I spend the time to reflect on the origins, and how its existence so often depends on an intricate set of interrelationships, I am equally awed and struck by the complexity of its construction. Things in this world are never as simple as they seem.
Vision Finding 3 - How we see the world is greatly influenced by context. Our perception of brightness, color, size and shape of an object will depend on the context of the object. You can make a grey object appear black, or appear white, simply by surrounding it with lighter or darker backgrounds. The moon is really not any larger at the horizon than at its zenith, yet the apparent size of the moon changes drastically in these different contexts.
The impact of context on perception reveals the rules our visual brain employs to create a representation of the real world. Perception is not reality. Our apparent visual reality is actually constructed by our brain based on rules developed from our past experiences and feedback from interacting with the real world.
This principle extends beyond vision. Everybody's apparent reality is different, because their reality is a representation of the real world based on personal experiences and interactions. To really understand another's reality on any issue, you need to understand how they are constructing it, which means you have to understand their personal history. And also, be aware that your representations about certainties in life are also constructed, and your life's certainties will change as your experiences and feedback with the real world vary over time.
Vision Finding 4 - is related to the role of context on vision. Our visual brain always resolves ambiguity by filtering information to derive a solution, but the solution is not stable and will change over time. We have seen reversible figures - vase-face image, mother-in-law/daughter etching, necker cubes, and Escher figures. This class of complex figures contains ambiguous information that allows for two different perceptual outcomes. For example, when shown the mother-in-law/daughter etching, one will say - "I see a mother-in-law", and then, "oh now I see a younger woman." And then little later, "it just flipped back to the mother-in-law." You see either the mother-in-law or the daughter, and it will switch back and forth, but you never see both at the same time. Nor can you voluntarily switch from one to the other. It just happens. Our visual brain filters some of the information to resolve the ambiguity, but it is not locked into the same solution indefinitely.
Much of what we deal with in this world is becoming more complex and more ambiguous, and we don't readily accept its ambiguity and complexity. We tend to resolve the ambiguity or simplify the complexity by filtering some information that leads to a certain perspective or viewpoint. And others will filter different information and construct a different solution. Moreover, we are incapable of handling simultaneously two contradictory or differing interpretations. But just like reversible figures, just wait and your constructed viewpoint will flip, and you will adopt a new viewpoint or perspective. You just don't know when it will happen.
Last Vision Finding - Individual visual brain cells are dumb. Isolated brain cells are ineffective and have only a very rudimentary capacity to encode visual information.
The power of the brain is derived from its interconnectivity. Every cell interconnects with many other cells - 10,000 other cells on average. The interconnectivity forms neural networks. Interactions among cells in the network make possible the elaborate processing that gives us our exquisite vision.
Neural networks are like social networks, and they both have two properties in common: plasticity and stability. Plasticity simply means that the connectivity depends on use. Multiple or repeated interactions establish new or strengthen existing connections; but if interaction ceases, the connection is weaken and broken. This is true in both neural and social networks. Individuals … like brain cells…must remain jointly interactive or connectivity is lost. So just like the etiology of many amblyopias, we can use our connections… or lose them.
The other attribute that networks provide is stability in dynamic environments. The impact of a single isolated event is diffused and modulated by other activity in the overall network. Think about the impact of community networks that diffused the suffering of individuals impacted by Katrina. I lost my father in January, and I am constantly reminded about the importance of my extended family network which enables me to accommodate to his death.
Tap into the richness and power of your networks. Be interactive and continue to expand your networks.
To conclude, let me share with you a clinic experience that probably some of you have also encountered. When I was faculty member in the School, I was asked to do specialized color vision testing. We often administered color vision tests to kindergarten boys who were brought to the clinic by their parents at the recommendation of a teacher. The teacher had noted that Johnnie was having trouble distinguishing and learning his colors. And almost always we would determine that Johnnie has a genetically linked color defect. We would share the diagnosis with the parents and tell them that Johnnie was born this way and he will confuse some colors. And if I heard it once, I heard it ten times from one of the parents who would then turn to Johnnie and say -"why didn't you tell me that you can't see colors?' And then Johnny looks at his parents esotropically.
In many ways, we share similar defects with Johnnie, being unaware that our world could be much more colorful and less confusing. Johnnie was born with a defect that is permanent. For us, our blind spots in life are acquired because our representations of the world are constructed based on our personal histories, and we reflexively filter information to simplify any complexity or ambiguity. Instead, we should embrace the complexity. Recognize that the world is very dynamic, and anticipate the changes. And if we always expand and interact with our network, the collective power of others in our network will provide the plasticity or capacity to continually adapt, as well as the balance and the stability to accommodate to this ever-changing, complex world.
Thank you for allowing me to talk vision, and I hope that this didn't sound just like another monsense lecture. Welcome to the profession.