FINAL BLOG POST

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:

Motion parallax in digital art

I found this video that shows one of the more complex monocular cues for depth.

This post is saturated with the brightest colors “hue” have ever seen

Disregard the horrible pun.

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:

That’s so immature

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.

The colors aren’t there

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.

A visual field that would drive me hopping mad

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.

Floatin’ on down the vitreous chamber

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.