I remember the day we went over Signal Detection Theory and thinking it was an interesting way to think about things. The suggested flexibility of this theory for use in almost any setting, be it professional or simply recreational pondering even today strikes me as extremely useful. I’m interested in many different fields so I pondered the theory once more today and thought about what I could possibly research to present in this blog. I have a natural propensity for math so it is not hard to imagine why I am now going to delineate the theory and propose several ways in which it can be utilized. The theory’s quantitative aspect increases its appeal because it is so objective with just a little bit of subjectivity, and that is what makes the theory so attractive to me as the topic for this last blog in Perception.

I would definitely be interested in applying the theory to something more applicable to daily life because I like quantifying things. I also immerse myself in world news and pass my free time by reading “The Economist,” chock-full of eye-opening stories about the world’s weekly events. What would be better for a math lover who likes to read about the world to do than try to spin a quantitative way on something that affects all Americans in an international way? I would like to discuss a situation I just recently experienced over Spring Break while traveling in India.

There exists a hit-and-miss struggle that security experiences when trying to keep the public safe by being able to distinguish or detect a signal over unimportant noise. I could not stop thinking about how this theory can be applied to this situation that people experience everyday in the dreaded Customs Department at the airport. It made me feel content that security thought the cost of taking some of the public’s time is less than the benefit of finding drugs or other harmful things, even cheaply made purses that people intend to sell for very high prices like in America. I can understand why this would appear to be a costly but very advantageous method to utilize in airports because honestly I could not help wondering how many times security overlooks things even though they already use so much of the public’s time to search.

The theory can be applied to the topic concerning the Customs Department at airports: How do the Customs security personnel exceed the cost of the public’s time with the benefit of keeping everyone safe? Also, how well are they doing? Are Customs security as successful as they appear? All these questions will be discussed in the duration of this discussion.

The importance of this question pressed me to investigate further. I found a great site (link) that hits on this exact topic I am discussing here. It appears that the benefit does exceed the cost, but since humans are the ones viewing the x-ray machines there is a degree of error. The site mentions some numbers:

• “Access to restricted areas: Access to parked aircraft achieved on over 67% of attempts (Dillingham, 2001).”

• “Detection of suspect items in baggage using X-Ray: 21% of items missed (Mead et al, 1987)”

• “Detection of suspect items on passengers using metal detectors: 17.5% of items missed”

Since about 20% of suspect items are shown to be missed, I was deeply surprised. Considering that everyone has to go through Customs when they return or enter a foreign nation, it is quite disconcerting to see such a high number of items be missed. I am definitely not alone on this topic, even by those studying the accuracy of Customs security. “Unfortunately, these confirm findings from industrial studies, that monitoring and decision-making tasks such as those that typify airport security tasks, can be disappointing” was how the writer of this article typified the instances of failure by security. I thought we were safer because of Customs! Are we really not as safe as I feel when I hand over my unopened bag of Indian fruit, a snack that I had really wanted to try in India but had saved for the plane back, to a stern Customs Department employee?

The bane of getting my precious fruit taken away from me leaves me hungry for more information on this topic…

Signal Detection Theory correlates to this situation. How you might ask? The signal is seeing a dangerous item. The criterion is whether it is dangerous or not. On the bell curve we saw that quantifies SDT and information regarding the actual study, either a yes or no to this posed question indicates whether the instance and accuracy of signal detection is present. SDT is a factor of the psychological aspect to studying perception. Furthermore, four instances regarding SDT and its relation to my posed question are important:

1. Since we are discussing SDT, the signal must be strong and very detectable. In the Customs department, unfortunately, drug dealers and enterprising new sellers of cheaply made foreign purses do not want us to see their item(s) clearly. That is why they resort to such covert actions as hiding drugs in gift vases that they can not open, for example. This creates chaos for Customs security which makes both dangerous signals and innocent signals blur together as one big mess. That is why my Indian fruit was usurped from me-That strange-looking treat could look like something that a person could imbibe and get high from despite the fact that it was innocent fruit. Clear contrast in the x-rays is key.

2. If there does appear a “borderline” item, the decision whether to check or forego checking this piece is important. This is for the discretion of the checker. Sometimes they are wrong, which leads to false alarms and misses.

3. “Vigilance declines” which means that viewers get tired and get accustomed to patterns like how we talked in class a few months before about how subjects can sometimes say no or yes when they do not even think very hard. This is human nature. It is desensitization.

4. Since there are not that many potentially dangerous items in luggage, the criteria adopted by security tends to be quite liberal which leads to many more false alarms, which is what I am disgruntled about now because of my snack being taken away from me.

In conclusion, however, I found (link) an article discussing current US Customs methods today:

“Last year, Customs started using Mobile X-ray Services (MXRS) at many of its ports of entry to improve the efficiency and lower the cost for screening travelers suspected of internally carrying illegal narcotics. Detection of these types of smuggling attempts can only be accomplished using x-ray radiographic technology. Customs has determined that it better serves the government and the public if the x-rays are performed at the port of entry. The MXRS van makes this possible by having onboard a certified x-ray technologist for taking diagnostic x-rays. These digital x-ray results can then be transmitted to a medical facility to be “read” by a board-certified radiologist. If the x-ray results are negative, the processing is complete and the traveler is released.”

“The current procedures require Customs officers, who suspect a traveler may be internally carrying contraband, to escort a suspect to hospitals or other medical facilities. Travelers are often held in emergency waiting areas until medical staff can administer the x-ray. Time, travel, and safety are some of the concerns Customs faces with this procedure. Customs is sensitive to the needs of the traveling public and makes every effort to expedite the inspection process, without compromising our enforcement posture. Our main objective with this technology is to release the traveler with a negative response quicker, which allows us to place our focus on the potential positive carriers. “

In conclusion, these previous two paragraphs show that the costs of “time, travel, and safety” are all being considered when people enter Customs, which reassures me that the fruit they took from me has helped everyone in the long run and kept everybody safe. (Note: Sarcasm)

Figure 9.14 on page 338 shows what Hans Wallach presented in his theory of the “aperture problem.” The aperture problem in A shows the aperture of a receptive field, which is inherently small, leading to a problem: when a “vertical bar moves rightward through the receptive field, the neuron would signal rightward motion” (Perception 338). There is a problem though, when this happens involving a presence of ambiguity. This is shown in B and C on the same table. In B, the bar is moving upward and to the right and in C the vertical bar moves to the right, yet downward. This proves troubling. Since the receptive field is described as “small” (Perception 338), the vertical bar is “relatively larger” and this means that you can’t distinguish that the bar is moving to the right and upward (B) or downward (C) or what you are looking for, straight and to the right (A) (Perception 338 ).

The textbook sufficiently notes that “So long as the vertical bar is large compared to the aperture (the receptive field), the same local spatio-temporal event-movement at the same velocity-could be genereated by any number of other combinations of fdirection and speed, some of which are sggested in panels B and C. This equivalence makes the neuron’s response inherently ambiguous. Because the neuron’s ‘view’ of the world is limited to the confines of its receptive field, the neuron responds exactly the same way to each of these different velocities of movement. ” (Perception 338 ).

This is all good and well, but what does this have to do with the real world and differing sized apertures-they are not always small and circular!

I found in the textbook that in figure 9.16 (Perception 340) the point that Hans Wallach made saying “how strongly the visual system favors a simple perceptual interpretation when alternative interpretations are possible” (Perception 339). Here there are 2 apertures side by side -a circle next to a rectangle. When a bar is passed down and to the left, at the beginning, the “line enters the circular aperture and is visible in both apertures simultaneously, the perceived direction in both apertures abruptly shifts, and the line appears to slide downward and to the left (as it would in the circular aperture alone) (Perception 340). This shows that “this change reflects the visual system’s effort to treat the line in both apertures as a single line moving in one direction, rather than as two separate lines moving in different directions. Once again, we find that vision favors simple perceptual interpretations, a general principle, which Josh McDermott and Ted Adelson have recently recast into a comprehensive quantitative framework (Perception 340).

In class we discussed John Keats’ view of Newton’s “unweaving of the rainbow” and how it saddened him to in effect “unweave the rainbow”. John Keats lamented this “unweaving” because he was in effect accusing Issac Newton of “destroy[ing] the beauty of the rainbow by explaining it” (link).

From the slides from class, was inserted the quote by John Keats:

“Do not all charms fly
At the mere touch of cold philosophy?
There was an awful rainbow once in heaven:
We know her woof, her texture; she is given
In the dull catalogue of common things.
Philosophy will clip an Angel’s wings,
Conquer all mysteries by rule and line,
Empty the haunted air, and gnomed mine -
Unweave the rainbow …”
-From “Lamia” by John Keats

This sufficiently shows the artsy nature of John Keats. I have my fair share of idealistic comments and beliefs, perhaps more than the normal person, but I still do not agree with his negative view on Issac Newton’s explaining the source and nature of light, and that white light is composed of all the colors. I think, in contrast to him, that it is more interesting to know the nature of something and WHY it is some way instead of trying to use my mere senses to like something. If I understand something I tend to like it more. This is the reason why athletes that are so successful love their job. They do not just wake up and are naturally good at their specific sport. They have to work to understand as much as possible.

I love watching “Top Chef” and I remember one very successful chef (as everyone who makes it on the show is) getting eliminated and his last stand included him saying, “If there is a day in my life that I stop wanting to learn more and get better than that is the day I really stop growing” which goes along with the well-known quote voiced by teachers and the like all around the world:

When you stop learning, stop listening, stop looking and asking questions, always new questions, then it is time to die. (link)

I searched more for some documented opinions on this topic and found that Richard Dawkins wrote a book entitled “Unweaving the Rainbow” and in a review for it is stated:

Inspired by the frequently asked question, “Why do you bother getting up in the morning?” following publication of his book The Selfish Gene, Dawkins set out determined to show that understanding nature’s mechanics need not sap one’s zest for life. (link)

It is useful to try to search for the cause of things and in effect this actually enhances one’s experience of something, for example a rainbow, as in this case. “Ignorance is bliss” could be at work here, but honestly, unless a person is an escapist or a young child, reality is so much more satisfying than any fantasy or delusion.

For example, knowing that a rainbow is all of the following from this children’s site makes me so interested in rainbows-even more so than if I randomly spotted one in the water near my car:

The rainbow is made up of all the colors of the visible spectrum. We can also see these colors by using a prism. When white light passes through a prism, it is bent. Each color is bent differently. Red is bent the least, violet is bent the most. The white light spreads out into its colors. Each color of the visible spectrum can be seen.

A rainbow is an arch of light exhibiting the spectrum colors in their order, caused by drops of water falling through the air. It is seen usually in the sky opposite to the sun at the close of a shower and also in the spray of waterfalls. In the brightest or primary bow, often the only one seen, the colors are arranged with the red outside. Above the perfect bow is a secondary bow, in which the colors are arranged in reverse order; this bow is dimmer, because of a double reflection within the drops.

When the sunlight enters a raindrop it is refracted, or bent, by and reflected from the drop in such a way that the light appears as a spectrum of colors. The colors can be seen, however, only when the angle of reflection between the sun, the drop of water, and the observer’s line of vision is between 40° and 42°.

This is so interesting! I truly love physics so maybe I appreciate this more than the normal person, but I embrace the union of science because without it we would be floudering around the world like fish out of water. We as humans thrive under a challenge, such as understanding our world and I think that the feat that Issac Newton overcame to explain the nature of a rainbow is admirable. “That’s one small step for man; one giant leap for mankind!”

I read further in the text and found that:

Inattentional blindness, and its related phenomenon, change blindness, not only underscore the limited capacity of attention but also disclose a very interesting property of perception.

This reveals how my lack of attention is significant to why inattentional blindness occurs, and moreso with a person as “focused” as I am. I realized that it “discloses a very interesting property of perception” though because it occurred in the videos that I saw here and here! I saw these two videos and was dumbfounded when I saw the first image of the video and the last after viewing them in their entirety and not seeing any visual difference the first time around.

I also remember learning in the text in chapter 2 that humans tend to see better when they are looking at something straight on and focusing their attention on this one point. The rest of the image (as in a video) is blurred which can account for this inattentional blindness.

I remember watching The Lion King when I was a child many times but never noticing how the sand flies up and spells out sex in lowercase, cursive type letters:

How did I never catch it? Maybe because I was not aware of the word at the time, but a more perceptually significant reason is because:

Most of the time inattentional blindness isn’t a problem. All we have to do is shift our attention.(p. 219)

Contrary to subjective impression, we do not continuously maintain a high-fidelity representation of the entire visual scene. We evidently lack the processing capacity to do so. Consequently, what we “see” outside the focus of attention is a rather sparse representation based in part on our visual memory of what was there when we last looked. (p. 219)

This reveals that this phenomenon occurs due to a lack of focus and how we tend to assume certain things, like how we don’t “commit the desk’s contents to memory because those contents remain visible as we work on them” (p. 219) like when we “straighten up the desk” (p. 219) so there is “no need to construct a complex, detailed visual scene inside your head when there is a perfectly good one right in front of your eyes” (p 219).

Also, I remember playing a very detailed hard game I wanted to beat and not seeing a person staring at me like they were angry and wanted to yell at me. I was in the zone, playing “Who has the biggest brain?” instead of paying attention to my entire visual field. If you asked me, I would have told you I was trying not to pay attention but in reality it was probably because I had gotten used to how they always looked angry and as if they wanted to yell at me so I had inattentional blindness to that person. There was “no need to construct a complex, detailed visual scene inside your head when there is a perfectly good one right in front of my eyes” (p 219)!

We discussed the duplex solution of vision in class. I wanted to learn about the consequences of the duplex solution of vision that we discussed in class and learned from the class textbook that the eye “contains two types of photosensitive elements” (Perception p. 97).

I read further and found that this means that one is “associated with the rod photoreceptors and provides high sensitivity to light” while the other is “associated with the cone photoreceptors that provide high resolution” (Perception p. 97). I found that the eye in humans have the “two types of film occupying somewhat different locations along the back of the eye” (Perception p. 97).

A couple of the most important consequences of duplex vision in humans that I learned was that “vision under dimly lit conditions is termed scotopic” (Perc. p. 98) and “scotopic vision signifies vision that depends on rod photoreceptors” (Perc. 98). Also, cones function if they receive more light than rods need to function correctly (Perc. 98). This contrast makes it so that when a human is under dim light conditions, the rods begin functioning more and more and the cones are used less. This kind of situation would be called scotopic vision.

Also, another consequence is that there is a “narrow, intermediate range of light levels where both rods and cones operate, and vision in this very limited range is termed mesopic” (Perc. 99).

The eye proves to rely on both giving good resolution and good sensitivity which are two choices that trade off when a person is utilizing vision (Perc. 99).

Apparently the number of cones per square millimeter decreases with distance from the fovea (Perc. 100), which means that when a human looks at a group of letters and stares at a particular letter in the middle of a group, the letters on the periphery appear less distinct (Perc. p 100).

The text indicates also that due to the duplex solution of vision in humans, decreased cell density and increased receptive field sizes guarantee that acuity will be worse in the periphery (Perc. p. 101). Having the duplex solution of vision, humans have a lot less acuity in the periphery of vision because otherwise we would have too many ganglion cells that would not fit in our head (Perc. p. 101).

I looked into this phenomena of the eye more deeply and found more information. Like I wrote in my last blog there can be possible defects in the way people view things. For example, I have astigmatism and others may have myopia or hyperopia. I found here that there can be a whole list of problems with peoples’ eyes. Myopia, hypermetropia, astigmatism, presbyopia, amblyopia, and strabismus.

These eye problems obviously cause problems in vision, which means that our perception would be altered if the presence of these defects were in our vision. This further stresses the fact that the eye is the slave of vision. On the other hand, though, our eye can be the master of vision. How is this paradox possible?

How can our eye be the master of vision?

This is the obvious answer to this question: We see the outer world via our retina, which is the “window” to our inner body. This means that the retina and our lens and our biological setup for vision all make us the master of vision because vision is vision because of the way our eye works to make us “see.”

I found further evidence for this here, and  read that:

The retina is a light-sensitive layer at the back of the eye that covers about 65 percent of its interior surface. Photosensitive cells called rods and cones in the retina convert incident light energy into signals that are carried to the brain by the optic nerve. In the middle of the retina is a small dimple called the fovea or fovea centralis. It is the center of the eye’s sharpest vision and the location of most color perception.

“A thin layer (about 0.5 to 0.1mm thick) of light receptor cells covers the inner surface of the choroid. The focused beam of light is absorbed via electrochemical reaction in this pinkish multilayered structure. The human eye contains two kinds of photoreceptor cells; rods and cones. Roughly 125 million of them are intermingled nonuniformly over the retina. The ensemble of rods(each about 0.002 mm in diameter in some respects has the characteristics of a high-speed, black and white film(such as Tri-X). It is exceedingly sensitive, performing in light too dim for the cones to respond to, yet it is unable to distinquish color, and the images it relays are not well defined.”(Hecht)

What does all this bolded text mean? I read it over and over and found that it is saying that biologically, the rods and cones (2 kinds of photoreceptors)  aide our vision perception.  This ensemble of rods and cones over the retina is very sensitive and performs in varying intensities of light! This means we are the master of our vision!

This interesting quote led me to investigate and find the paradox that is the eye is so interesting. I have truly learned a lot more about vision.

I always wondered how astigmatism worked, when my contact lenses appeared blue while my friends’ were clear. Only one of my friends had the blue-ish lenses that matched my very own. I found from this site that contact lenses work as corrective lenses:

Contact lenses are thin, finely crafted plastic discs designed to fit over the cornea (See Anatomy of the Eye) of the eye, usually to correct vision problems caused by refractive error. They are held in place by a natural layer of tears on the surface of the eye. In addition to their obvious cosmetic advantages over eyeglasses, contact lenses provide better peripheral vision and virtually eliminate the image distortion sometimes caused by eyeglasses. Contact lenses are now available for the correction of most vision problems caused by refractive defects of the eye including nearsightedness, farsightedness, astigmatism, and presbyopia.

This means that contact lenses are skinny corrective frisbee-esque discs that lie on my cornea! I had no idea. I perused more sites and found more about my condition (surprisingly common as I found at this site…

Astigmatism is a very common yet frequently misunderstood vision problem.

Astigmatism appears to be common. I felt better after reading this but wondered what made it a vision problem. Why are MY eyes different from normal-visioned people?

The same site showed me that my cornea is like a “football” (like the below quote shows). This means that my cornea is shaped like a football instead of like a perfect sphere like a baseball. A person with astigmatism like me has a problem with the cornea directing light directly at a particular point in the back of the eye like how we learned in class. My corneas, therefore, are not periodly curved like in a sphere. Because of the irregular curvature, corrective lens are an effective and very common solution to astigmatism.

An analogy that is commonly used to explain astigmatism is to compare the shape of your cornea to a football or a baseball. If you have astigmatism, your cornea is shaped more like a football (or the back of a spoon) than a baseball. Like a football (or a spoon), an astigmatic eye has unequal curvature in different meridians. In contrast, a baseball is a perfect sphere with equal curves in all meridians.

Ok, so now I know what my astigmatism means-my eyes’ corneas are irregularly shaped and resemble a football shape inside. How do these corrective lenses seemingly magically correct my vision to be normal?

Since according to one site, ” Astigmatism usually occurs when the front surface of the eye, the cornea, has an irregular curvature.” I found that corrective lenses are not needed for slight astigmatism but for people like me, where the curvature of the cornea is pretty mishapen:

The corrective lenses needed when astigmatism is present are called Toric lenses and have an additional power element called a cylinder. They have greater light-bending power in one axis than in others. Your eyecare professional will perform precise tests during your eye examination to determine the ideal lens prescription. Refractive surgery may be able to correct some forms of astigmatism.

Therefore, my lenses are toric lenses and they can bend all the light that is going at different points at the back of my eye into a more precise location! The “greater light-bending power in one axis than in others” have this “cylinder” which makes the light be affected.

I finally understand what makes my blue lenses different from those of my plain clear-colored friends’ and I do not feel like it is a stigma anymore!

There is more than meets the eye, I see the soul that is inside.

I was so astonished because I had always sang along by saying “I see the hole that is inside.” I thought the song was all about a girl who rejected a boy and was shunning him and proud of it while she was in reality, I see now, was really suffering her loss. How could I have misunderstood the lyrics and thus the very point of the song so badly? I blame it on the inaccuracy of our hearing now, because while humans’ hearing proves good enough for our daily life, it is definitely not for trying to distinguish almost indistinguishable signals from senseless and loud noise.  Like we learned in Perception class, I reflected on how our hearing is based on (in the case of the human’s daily life at least) a variety of noise with different frequencies that clutter up the true perception of a signal, or in this case, the words that Avril was trying to convey to her listener, me, in this case.

I remember another time my friend and I were arguing over the true lyrics of my favorite band, Linkin Park’s song “In the End.” I was absolutely sure that I heard the lyrics to be (and google helped me prove I was right at this site):

(It starts with)
One thing / I don’t know why
It doesn’t even matter how hard you try
Keep that in mind / I designed this rhyme
To explain in due time

On the other hand, my friend began making me doubt myself and the lyrics that I was so sure I heard. She insisted that she had heard in the last line: “To explain to you time.”

I found myself so confused because if this was true, the whole song’s theme and message were altered. I sat in disbelief but held firm that I was right. I am glad I did because this mondegreen of a lyric would have thrown my perception of the song because the immediacy would be lost and replaced with a different sense that makes the song didactic, something I cannot stand. This could have forced me to lose my interest in Linkin Park and I don’t know where I would be today if that were the case!

On a different note, I listen to a lot of Spanish music and I will provide an example of a Spanish song I spent hours trying to successfully understand (or hear in this case) to further my message of how mondegreens can ruin peoples’ perception not only of lyrics but also of messages of songs which can ruin fans’ lives! I was listening to a song named “Atrevete” by Calle 13, and realized that instead of it being a feel-good Spanish song, it was a song calling for all to “dare” to speak up and raise your voice, I looked at the translation and realized it was a rather crude song with lyrics meaning something quite on a different topic that made me lose interest quickly in the song as well as in the artist.

Lastly, a very popular song that I kept hearing about is “Tiny Dancer” so I decided to listen to it. After hearing what was supposed to be “hold me closer, tiny dancer,” I was puzzled because the song definitely made me believe that the singer was saying “Tony Danza.” What does Tony Danza have to do with the song Tiny Dancer? Nobody knows, but Elton John is really singing tiny dancer, which I should have known by looking at the title of the song.

It appears mondegreens plague my life more than I thought, but alas, it is a result of humans’ less accurate hearing compared to other animals that need hearing as a major sense, unlike a “minor sense” according to what our textbook Perception tells us.

Back to Helen Keller’s quote, though, leads me to conclude that she is right. Blindness cuts you off from things because even when you touch a person’s face, like with the President’s, you can conclude things and features about a person’s face. On the other hand, you when you interact with a person, you can hear in their voice inflections that show the sorrow a person has, like when the President is ecstatic about winning an election or when he is lying and he is stuttering. Helen Keller reveals the  vast importance of sound and the art of hearing when she says this quote. Sound is not able to be compensated for by other senses. It is unique and unlike Immanuel Kant, the famous philosopher, it IS important and is not one of the most “dispensable senses we as humans have.”