Perhaps one of the most interesting topics we discussed in this course was echolocation, specifically the rare application by humans. I was simply fascinated that humans with impaired vision could actually take advantage of their sense of hearing to “see” the world around them. I understood that dolphins and bats used their versions of echolocation or sonar, but the idea that blind humans could use it as well was, in a word, unreal. I’ve done some research on the whole idea of echolocation to shed some light specifically on the process as it works in those few humans that can do it.
The basics of echolocation are fairly simple to understand, and it works much like man made sonar technology. Select animals, like bats, shrews, dolphins and whales, produce high frequency sounds that travel outward toward the animal’s immediate environment. Those sound waves echo, or bounce back off objects and structures in the environment, and the echoes are interpreted by the animal into “images” of the surroundings. Here’s a very basic picture of echolocation:
I found the concept of categorizing color very intriguing. Unlike some of the models we have seen for other senses, like the Henning prism for smell, this one has a good deal of weight based on the empirical evidence. Known as the HSB cone for measuring the hue, saturation, and brightness of a color, it is alternatively known as HSL (with lightness), HSV (value), or even HSI (intensity). For the purposes of our course, we have worked with the HSB cone.
I think this is a great visualization of color variance, and it highlights and explains some of the subtleties of color that are hard to grasp otherwise. There are, however, other graphic representation of these color characteristics, and they follow:
I was very interested in yesterday’s lecture from Mary about underdeveloped vision in infants. She informed us of some potential reasons why human and the similarly structured macaque monkey infants do not have the level of visual perception that the corresponding adults do.
We examined the tests done through the visual system, from the retina to the cortex, and Mary pointed out that while at birth there are some underdeveloped aspects of the retinal neurons, the supercolliculus, and the lateral geniculate nucleus, the affects of these immaturities are eventually corrected within about 2 to 4 weeks (in macaque monkeys). This means that the “answer” to the visual development question lies in the cortex.
We haven’t really discussed color perception, but I found a cool illusion online that demonstrates a concept called chromatic adaptation, more specifically color constancy. Check out the video:
Like the video states at the end, the second image is black-and-white, but we initially see the “true” color version of the picture. Color constancy is really just a certain type of light constancy, a concept we have discussed already.
Basically, we can view the same object in a variety of different light settings. Our ability to recognize the object as the same object in environs of various illuminations is due to an adaptation mechanism. This mechanism can require some time to kick in, which explains why we cannot see objects well when we initially enter a darkened movie theater on a sunny day. After our vision adapts, we are able to recognize objects better.
With chromatic adapation and color constancy, we recognize that an apple is red whether the illumination is the white sunlight of midday or the darker light of sunset. Despite this, chromatic adaptation can be manipulated to allow us to “see” colors that aren’t actually there, as demonstrated in the video. The colors presented in the first image condition our eyes to see the colors in the black-and-white image before we “un-adapt” and see the second image for what it is.
Check out some more of these illusions at StareClips.com.
In honor of Easter, I thought it would be good to look into how rabbits see differently from humans. I began Googling, looking for some information about rabbit vision. I found an interesting article by Mike Chapman from the Wisconsin House Rabbit Society website about some of the characteristics of the vision of a prime example of natural prey.
I wanted to write about this last week, after hearing a little about floaters in the week before Spring Break. I’ve always been haunted by those little spots in my vision, and they irk me especially right after I look away from some kind of light source. So, I started my search in the text and on the internets for some more information.
In the Blake and Sekuler text, the authors described floaters as “small opacities that float about in the vitreous,” identifying the opacities as simply “debris”(Blake & Sekuler, 2006). It’s a definition that suffices for our class, but I wanted to know a little more about what constituted this debris. Keep reading →
My mom got LASIK surgery a few years ago, and as soon as I can afford it, I want to get it for my eyes, too. I learned a little about LASIK when my mom got the operation, but I didn’t know enough about the eye to really understand it. So, I did some research (okay, some “Wikisearch”) and found out a little bit more about the procedure.
LASIK stands for Laser-Assisted in situ Keratomileusis, and it is a type of laser corrective eye surgery for correcting myopia, hyperopia, and astigmatism. Development of the technology began as early as 1950 with the invention of the microkeratome, a small surgical blade that can cut and reshape the cornea. After nearly four decades of research and development, Dr. Gholam A. Penyam received a U.S. patent for LASIK in 1989. The surgery was developed over the next year by Lucio Buratto and Ioannis Pallikaris. Today, there are many variations of the basic LASIK surgery as lasers have become more powerful and more precise.
I was thinking about the Helen Keller quote that Professor Boucher showed us at the beginning of the lecture on Wednesday: “Blindness cuts me off from things; deafness cuts me off from people.” I think there’s a lot of wisdom in this. When we interact with our environment, we rely on all five of our senses. It seems that the sense of sight would be the most important for living a “normal” life, and that the loss of sight would perhaps be the most devastating.
That Keller, who was both blind and deaf, would seem to value her hearing more than her sight speaks a lot for the sense. I think her point in that statement was that the ability to see, touch, smell, and taste allows us to interact with all of the objects in our lives, but that they don’t connect us to the people in our lives. Almost everything that we see is based on the physical and material properties; hearing the voices of others, however, connects us with the immaterial hearts and minds of other people. The connection we get from this ability to hear the ideas and feelings of others is a large part of what makes us human.
I set out this week to find out why most people have a strong, almost involuntary reaction to eating sour foods. Think about the last time you ate a sour grape, a Sour Patch Kid candy at the movies, or even a lemon; your mouth puckers up, your eyes squint and sometimes even water, and you have to fight with all of your being not to look completely stupid.
The truth is, scientists really don’t know much about the sour taste as it is. In 2006, researchers at the Howard Hughes Medical Institute in San Diego were finally able to identify a single, specialized receptor in the tongue for the sour taste. Bitter, sweet, and umami taste receptors had been identified previously by scientists, and they all work similiarly. These three tastes are carried by large molecules, like sucrose, that made finding specialized receptors in the tongue easy to locate. Both the sour and salty tastes work differently, with these perceptions triggered by ions like hydrogen (H+) for sour tastes and sodium (Na+) for salty tastes.
