FINAL BLOG ENTRY

Throughout this psychology class I learned many new things about human perception. However, one piece of new knowledge that especially intrigued and interested me was the phenomenon of synesthesia. Synesthesia is derived from the Greek “syn” meaning with, and “aisthesis” meaning sensation. Merriam-Webster defines synesthesia as “a subjective sensation or image of a sense (as of color) other than the one (as of sound) being stimulated”. In other words, stimulation of one sense leads to the stimulation of a secondary sense.

Synesthesia was first reported by the scientific community in the 1880’s by Francis Galton. After the initial reports, synesthesia was widely studied by scientists in England, France, Germany, and the United States. However, as behaviorism became more popular in the 1930’s, and subjective internal experiences became largely criticized, the study of synesthesia waned. In the 1980’s the study of synesthesia once again went under way, due to the emergence of the cognitive revolution.

The most common form of synesthesia is grapheme-color synesthesia. In this specific form, letters and numbers are associated with certain colors. The letter/number-color associations vary within each individual however there are some cases where certain letters are more commonly associated with colors (for example, the letter A is commonly associated with red). Many times people afflicted with this type of synesthesia do not know that it is out of the ordinary. They often first learn about their synesthesia when talking to others and assuming that they too have these color associations. Many people with grapheme-color synesthesia say that the sensations are helpful in their every day lives. Many times the condition serves as a memory aid for remembering names and telephone numbers.

Another form of synesthesia is sound-color association. Sound-color synesthesia is often divided into two groups, narrow band and broad band sound. In narrow band, musical notes, timbres and keys, are associated with certain colors. Although in this synesthesia, like grapheme-color, associations vary by individual, in large samples a trend can be seen where higher pitched notes are associated with more bright colors. Broad band sound synesthesia is where environmental sounds, such as a door closing, or a car’s horn, are associated with visual colors.

One form of synesthesia which is less common is lexical-gustatory synesthesia. In this form, of synesthesia, auditory words or phonemes are associated with sensations of taste in the mouth. Scientists believe that this synesthesia is developed by childhood food experiences. Many times the sounds are associated with the foods, for example in one subject, “n” and “s” triggered the taste of mince. The phonemes can also however be completely unrelated, such as “f” and sherbert. Ward and Simner, devised an experiment to show that the taste associations were related to phonemes and not to specific letters. For example, the same subject associated the taste of egg with the “k” phoneme, when spelled with a c (such as in the word accept), k (such as in the word York), ck (as in Chuck), and x (as in fax).

Many studies have shown that synesthesia is genetic and that it clusters within families. Additionally, women have a higher rate of synesthesia than men, however this has also been attributed to the fact that women are more likely to disclose their condition. Studies have suggested that there is an X-linked model of inheritance although research is still preliminary.

The neural basis of synesthesia is that different areas of the brain “cross-talk” with each other in those with synesthesia. For example, lexical-gustatory synesthesia can be attributed to irregular connectivity between areas of the insula, involved in the perception of taste, with the temporal lobe regions that are involved in auditory perception.

I think synesthesia is very interesting, and initially I was wary about its genuineness. However, synesthesia is very hard to fake. The book mentioned a test where certain patterns of letters are much more quickly picked up by those with synesthesia because of the color correlations. My skepticisms were instantly erased and I became very intrigued in the subject matter. Now that I have more deeply researched the subject, I further appreciate the disorder. I am still deeply curious on what exactly the world would be like if I personally had a form of synesthesia, but for now my research has given me much insight.

UPDATE:

Sources:

http://psy.ucsd.edu/~edhubbard/papers/Hubbard_Neuron05.pdf

http://cytowic.net/_Books/__More-Synesthesia/__more-synesthesia.html#Top

http://www.synesthesie.nl/pub/personal%20profiles.htm

http://mitpress.mit.edu/catalog/item/default.asp?ttype=2&tid=11303

Color Deficiency

Studying for the final test, I was deeply fascinated when reading about color blindness, or more accurately color deficiency, and decided to do some additional research of my own to further go in depth with the subject. One form of color deficiency that was not covered in the book is tritanomaly. Similar to protanomaly (L-cone defect) and deuteranomaly (M-cone defect) t is a form of anomalous trichromacy which is characterized by a S-cone defect. Anomalous trichromacy means that the person is a trichromat but one of their absorption curves is abnormal. In the case of tritanomaly, the absorption curve for the S cones, which normally peak at around 430 nm wavelengths, is abnormal in some way. I also read about rod and cone monochromacy. Someone with rod monochromacy has only rods in their retina and therefore cannot see colors in normal daylight illumination. Cone monochromacy is where an eye only has a single type of cone in their eye and cannot differentiate between hues. There is no reported case of an eye only having cones.

One question that I came up was if there were any cases of anomalous trichromacy with multiple absorption curve defects. I was pondering what vision would look like to someone that had all three of their cone types working but completely messed up. Sadly, I could not find such a case.

Another thing that interested me was congenital supernormality. The book claimed that some people could technically have tetrachromacy for genetic reasons. I also further researched this and found an article that stated that around 2-3% of the world’s women might be tetrachromatic. The article stated that the average person can see about 1 million different hues whereas a tetrachrome can see up to 100 million different hues. This fourth cone lies between the L and M cones, in the orange range.

Development of Vision

The development of vision in humans is both driven genetically and environmentally. The ability to see sharp, be able to focus (accommodation), eye muscle coordination, and binocular vision are developed within the first year of the child’s life. Experiments with animals that are similar to humans have helped us understand the development of vision far better. One of these animals is the cat. Cats have visual systems that are very similar to ours. In one experiment by Nobel Prize winners Hubel and Weisel, they affected a cats vision for a long time in a certain way. These alterations of vision included patching one eye, blurring an eye with a contact lens, or misaligning the cats eyes. The cells that were binocular became monocular due to the alterations. Additionally, visual acuity, and color and depth perception in the cats was reduced dramatically.  If these disruptions in vision happened while the animal was still developing many times the cells atrophied and the effects were permanent. This time where the animal is still developing visually is referred to as the critical period, the time period of maximum neurological plasticity. For humans this critical period is just after birth until about 2 years of age. The article that I read compared visual development to learning a new language. During the critical period, visual development is natural and spontaneous, similar to learning a new language. Although still possible, visual development is very difficult past the critical period.

Source: http://www.strabismus.org/critical_period_Hubel.html

Vision Article

A new study by the American Optometric Association (AOA), released last Friday, brought up the concern of “computer vision syndrome”. This syndrome is marked by dry eyes, eyestrain, neck and backache, light sensitivity and fatigue. There are multiple things that can cause computer vision syndrome, most commonly the habit of using the computer in a poorly configured working environment. This can include improper lighting and simply being on the computer for too long without taking a break. The AOA additionally put out a survey which stated that 82% of Americans use a computer or handheld device with a computer screen (such as a PDA) frequently. Along with this 42% of Americans spend 3 or more hours in front of a computer or similar device. Also, 78% of Americans do not have their computer monitor at the correct and safe height, in relation to their eye level. Optimally, the screen should be below eye level. Adding to computer vision syndrome is the presence of other eye problems, with those that are undiagnosed being the most serious. Dr. Kent Daum, optometrist for the AOA, stated “The constant re-focusing effort stresses the eye muscle, leading to computer-related vision problems. It can have a great impact on individuals’ comfort and productivity, whether they are at work, school or home.” Another problem is that often times the picture on a computer screen is less defined and sharp than that of a printed page. This causes even further strain on the eyes.

Many Americans say they are experiencing the symptoms of computer vision syndrome. In the AOA survey, 41% said they have experienced eye strain and 45% said they have experienced back and neck problems from using the computer for too long. Although, fortunately most of the symptoms are temporary, some can be permanent and cause very serious problems. The AOA recommends that computer users take several steps to protect against computer vision syndrome. These include having your vision checked regularly, limiting the amount of time you use the computer, making sure the monitor height is set up properly (15 to 20 degrees below eye level and around 20 to 28 inches from the eyes), elimination of glare, reducing light to match the monitor light, and making an effort to blink constantly.

As someone who uses a computer screen for many hours in the day, doing schoolwork or other things, I find this article very interesting. On one hand, having recently read all the chapters about vision, I understand that keeping my eyesight good is very important. However, on the other hand I feel that “computer vision syndrome” feels somewhat made up and that the symptoms are just logical byproducts of the activity of using a computer. It is pretty obvious that staring at a computer screen and sitting in the same position for several hours will give you eye strains and body aches. But when I finish playing a game of soccer I don’t say I have “soccer playing syndrome” because I am tired and short of breath. Also, the steps recommended by the AOA to combat computer vision syndrome are either very obvious (don’t use the computer for too long, get your vision checked) or too minute and ridiculous to ever do (make sure the screen is 15-20 degrees below your eye level, remember to consciously blink a lot). However, in the context of the information I have learned in Perception class, I found it an interesting article to read.

UPDATE: forgot the source link: http://www.medicalnewstoday.com/articles/101348.php

Vision Cont.

1. What is cortical magnification and is it a good or bad thing?

Cortical magnification is the distortion in which representation of the center of the visual field is highly exaggerated. This means that a large portion of the cortex is devoted to a very small area of the retina. This area of the retina is known as the fovea. On the fovea, the central portion of the visual field is imaged. The cortex is responsible for much acute vision. Cortical magnification is a very good things because it allows humans to focus in on where they are looking. If the representation of the center of the visual field was not highly exaggerated then humans would not be able to see things as sharp as they could now. On the other hand, if everything was as visually sharp as the center of the visual field then the brain would be overwhelmed with information.

The duplex solution of vision:

The “film” in the eye is duplex, which means that the eye has two different types of photosensitive elements. One of these photosensitive elements is related to the rod photoreceptors and provides the eye with high sensitivity to light. The other, is related to the cone photoreceptors and provides high resolution.

One theory of visual perception that was proposed in a research article released in 1992, claimed that there was a split in the visual pathway between visual control of action and visual perception. This “perception-action” hypothesis has been backed up by neuroimaging experiments, human neuropsychology, monkey neuropsychology, and human psychophysical experiments. Behavioral experiments have shown that “visually guided actions are largely refractory to perceptual illusions.” This has remained an interesting, yet controversial theory over time.

Oblique effect:
The oblique effect refers to the superiority in visibility of horizontal and vertical lines. Some people however, do not experience the oblique effect. Some people with astigmatism see oblique lines more clearly. There are two theories as to why most humans have a bias for horizontal and vertical lines. One, the “nature” theory, argues that humans receive more exposure to vertical and horizontal lines as they are growing both in indoor and outdoor environments and this is why we have the preference. This theory was backed up by an experiment with kittens where they were removed from vertical lines and later on in life did not show the preference. The second theory is that genetic factors are the reason for the oblique effect. This is backed up because infants that are very young exhibit the same effect. The true answer probably lies in between both.

Limits of Vision

1. Roger Carpenter said, “The eye is at once the master and slave of vision.” What did he mean by this?

I believe what Dr. Roger Carpenter was referring to, is the notion that our eyes while giving us vision, also limit what we can perceive visually. The human eye is the organ that allows us to perceive the world visually. However, in the same regard, the human eye limits what we can see. Humans can only perceive light wavelengths of 400 to 700 nanometers, as opposed to many other creatures whose eyes can perceive far different wavelengths. Humans are also limited by the visual acuity of the human eye. Some animals, for example birds of prey, can see far more accurately than humans. This is for biological and evolutionary reasons; birds of prey require their sharp vision to hunt for food.

I found an interesting website which argued that our vision is essentially limited by the temperature of the surface of the sun and the strength of gravity on the surface of the earth. The temperature of the surface of the sun determines the wavelengths of light that are emitted, and the strength of gravity on earth “sets the composition of the Earth’s atmosphere”, which determines what wavelengths of light get through the atmosphere. However, this explanation is more of a environmental limit to vision than a anatomical limit.

Another limit to human vision comes from the size of our eyes. While the pupil can change size depending on numerous factors, the average diameter of the pupil is 0.5 cm. Therefore, “The smallest angle we can observe directly is given by the ratio of the wavelength of light to the diameter of the detector”.

Understanding the human limits of vision is important for many reasons. One of these reasons is eye witness testimony in criminal courts. Many times people far overestimate their visual ability. However, technology has enabled criminologists to take this factor into account. Bluriness and distance are equivalent to the visual system. Therefore it is possible to take a larger picture and make it blurry to the point where it would be equal to someone from a certain distance viewing it. This has made a difference in many cases, such as a 1999 trial of a beating that was overturned because the eye witnesses were too far away to give accurate testimony. I think this is interesting because of how this information could have been used in previous trials before the technology was invented. Many innocent people could have been convicted and put to death because of misunderstandings in the ability of human vision.

sources: http://www.medicalnewstoday.com/articles/20064.php, http://www.swift.ac.uk/vision.pdf

It’s all in the eyes

How do contact lenses really work?

People, such as myself, who do not have perfect vision there is a problem between the length of the eye and its refractive power. Due to this, the eye experiences a refractive error, or an error in the focusing of light by the eye. Contact lenses work by focusing the light properly on the retina. Contact lenses work by fixing this error and properly focusing light on the retina. Contact lenses are held in place with the eye’s natural tears.

2. Investigate your favorite optical illusion and find out why it works the way it does.

My favorite optical illusion for years has been the color constancy illusion. More specifically the checkerboard shadow one that was shown in class, with the comparison of the A and B squares. Color constancy works because the human brain and its color perception system works to make sure that human perception of colors remains relatively constant under various conditions of light illumination and shading. The human brain does this to aid in identification of objects. The cone cells of the eye register different ranges of wavelengths that are reflected by the objects in the scene that is being viewed. When this information is gathered, the brain then decides on the composition of the light throughout the scene. Once the illumination is understood the brain then discounts it so that it can perceive the actual color of the objects.

3.  The eye has been likened to a camera.  Where does this analogy succeed and where does it fail?

The eye is similar to a camera in many aspects. Both have an opening for light to enter, in cameras this is the aperture, in the eye a pupil. Both control the amount of light entering. This is done by the diaphragm in a camera, and the iris muscles in the eye. Both refract light, in cameras via the glass biconvex lens, and in eyes the cornea. Both use light to form an image. Cameras use photosensitive chemicals on film whereas the human eye uses photoreceptors in the retina.  Both also absorb excessive light to prevent formation of multiple images. The main difference between the human eye and a camera is in the focusing mechanism. Whereas a camera changes distance between the lens and film, the eye changes focal length of the lens using ciliary muscles.

Source: http://library.thinkquest.org/28030/eyeevo.htm

Hearing

1. We talked about some uses for hearing. What do you think is the best use for hearing?

I think the best use for hearing is communication. Hearing is vital in allowing humans to communicate with one another. The ability of humans to speak is one of the major discerning traits that separates us from animals. Having diminished, or lack of hearing would be devastating to communication between others. Additionally, I think this ability to communicate has allowed humans to advance as a species to what they are today. Without hearing, and thereby communication, almost all of the technological advancements made by humans would not exist. Furthermore, hearing and communication are essential for survival. No species as advanced as the human race could exist and evolve without the ability to hear.

2. Helen Keller said, “Blindness cuts me off from things;deafness cuts me off from people.” What do you think about this statement?

I think this statement very much oversimplifies the ability to see. Although, it is very true that the lack of hearing cuts off much communication with other people, the lack of seeing does so as well. And while there are ways to overcome lack of hearing, such as sign language, it is very much harder to overcome lack of sight. I think the reason that Hellen Keller made this statement is because she never had the ability to see, and therefore did not fully understand how important of a sense it was. While hearing is not easy to describe to those who have always been deaf, I think that seeing would be far more difficult to describe to those who have always been blind. In essence, if I had to choose between the ability to see or the ability to hear, I would easily choose sight because of its importance in everyday life.

3. One of the roles of the acoustic reflex is to dampen one’s own voice. Why do you think this is important?

I think the role of the acoustic reflex in dampening one’s own voice is very important. If we heard ourselves as others heard us, we would constantly be overwhelmed by the loudness of our own voice. Additionally, we would not be able to hear specific sounds and would be annoyed by the loudness and sound of our own voice booming over every other sound.

Smell

1. We talked about the commercialization of smell. How, if at all, do you think smell influence your buying behavior?

I think smell plays an important part in the buying behavior of myself and all people. For example when I smell food that has a pleasant odor coming from the rooms of one of my hallmates I ask them what food it is and where I could purchase it. This is because food that tastes good is often related to food that smells pleasant as well. Some related smells however, have no direct relation to the quality of their product. For example, I really enjoy the smell of new books, even though technically a new book would have no real quality advantage over a book from the library. One interesting article that I read showed research from Dr. Alan Hirsch, a director of neurology at the Smell and Taste Treatment and Research Foundation in Chicago, who found that the smell of flowers increased the percentage of people who said they would buy a pair of sneakers by 84%. This is an even more surprising case. In the example of new vs. old books, although the smell does not signify a change in practical quality (that is the words on the page), it at least signifies that the book is newer and therefore could be higher overall quality (ex: the binding of the book). In the case of the sneakers however, the smell has no relation to the product whatsoever, yet it still largely impacts purchasing decision. One explanation of this is that smells are closely linked to emotions, and that the area of the brain that plays a large role in smell, the limbic lobe, also plays a large role in emotions. Malls take advantage of this fact by pumping air that will drive customers to buy more products.

2. What is your favorite type of smell and why?

My favorite type of smell is the smell of new products. It does not necessarily matter what it is, new cars, new sneakers, new books, I just enjoy the manufactured fresh smell. I do not know why I enjoy the smell. My guess is that the smell has been associated with receiving gifts, and things that are new and novel. I also very much like the smell of food when I am very hungry. This is obviously because I want to eat the food that is emitting the enjoyable odor.

1/13/2008

How do you exploit your senses for enjoyment?

There are many ways to use ones senses for the sake of enjoyment. One way is through venues of entertainment. For example we use our sense of hearing to listen to music, an activity which most, if not all, people enjoy. Another example, which uses more than one sense, is television. In this case we use both our sense of hearing and our sense of sight for entertainment and enjoyment. All of the senses can be used for enjoyment. It is very enjoying to eat and taste a delicious meal. And the sense of touch can be used for enjoyment in many ways as well, one example being a massage.

Another way human beings exploit our senses for enjoyment is by altering them. The usage of drugs to exploit human senses has long been in history. For example, psychedelic drugs such as LSD and psilocybin (the chief ingredient in psychedelic mushrooms) can cause visual hallucinations, an altering of the sense of sight. Another example is MDMA, or ecstasy, which alters human hearing of music and makes it more enjoyable. Almost all human senses can be altered by the use of drugs for human enjoyment.