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OfflineXUL
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Boundary Extension and Top Down Processing
    #20551918 - 09/11/14 07:13 AM (9 years, 4 months ago)

Boundary Extension: Initial Inquiry


Boundary Extension



I chose to examine boundary extension, which is a simple example of how our existing knowledge of the world plays a role in how we perceive. Boundary extension shows us that when we visually perceive a photograph, we often remember it inaccurately. Our inaccurate memory of the photograph is usually one with a wider boundary – thus boundary extension. The perceptual and cognitive bias that leads us to remember a picture inaccurately exists because of top down processing, which is processing based on former knowledge. Boundary extension shows us that, as human beings, our perception of the world is not an exact depiction of what is real, but rather a combined outcome of visual perception and cognitive processes.

Carmela V. Gottesman and Helene Intraub (1999) refer to boundary extension as, “a tendency to remember seeing a greater expanse of a scene than was shown in a photograph” (Gottesman & Intraub, 1999, p.86). Gottesman and Intraub believe that this phenomenon exists because of the viewer’s expectations of the photograph. Specifically, when a viewer is shown a stimulus photograph (a close up view) and then asked to draw the photograph, the viewer has a tendency to draw the photograph as being wider than it was in actuality. It is important to note that clinical patients with damage to the hippocampus (which relates to memory) are not as susceptible to boundary extension. Sine´ad L. Mullally, Helene Intraub, and Eleanor A. Maguire (2012) confirm this idea in their investigation of patients with hippocampal damage: "Seven patients with selective bilateral hippocampal damage and amnesia, who cannot imagine spatially coherent scenes, displayed attenuated levels of boundary extension on three separate measures. Paradoxically, this reduced boundary extension resulted in better memory for the stimuli compared with matched control participants, because the patients’ recall was less encumbered by the boundary extension error" ( Mullally, Intraub, & Maguire, 2012, p.261). The idea that memory plays a role on boundary expansion is important because it further illustrates that cognition (top down processing) is an important part of perception. Furthermore, it reinforces Gottesman’s and Intraub’s idea that boundary extension exists due to expectations, which are indeed cognitions.

Gottesman and Intraub (1999) state that at any given moment a human being is not able to view a scene in its total. Visual acuity is most accurate when the stimulus reaches the fovea, which is an area of the eye made up of cone receptors and known for its ability to create sharp detailed perception. In contrast, light that does not directly hit the fovea becomes more peripheral. Since visual acuity lessens in the peripheral area of vision, we use perceptual schemas to fill in those areas. Boundary extension is believed to occur because peripheral areas of vision are essential to our comprehension of the world around us. Because our peripheral area of the eye lacks acuity, we compensate for this by creating perceptual schemas.

It is important to note that boundary extension is maximized whenever an image is cropped very small and has a background which could be considered continuous. Boundary extension is minimized when an image is large and already shows much of the background. Pointing out that viewing a photograph is comparable to viewing the world at any given moment, Gottesman and Intraub (2012) state, “At any given moment, the human observer is not able to view a scene in its entirety. With each fixation, a new region of the scene is brought into view” (Gottesman & Intraub, 1999, p.88). Thus, depending on what or how you are looking atsomething, you will experience more or less boundary extension – a perceptual and cognitive error.

Boundary extension is a visual phenomenon that demonstrations how we use top down processing to help ourselves perceive the world. That is, we use what we already know about the world to create a more complete idea about what we perceive. Even though we are creating more complete perceptions of the world, in actuality we are not creating identical perceptions of the world. Since we our eyes are only able to process the world in fixations, boundary extension plays a role in helping us understand the world. We constantly sample the world with our eye fixations and at the same time use our cognition to anticipate how we expect the world to be. Our bodies run an a continuous process of perceiving and thinking. And perhaps this phenomenon may have some evolutionary significance.

As an aside, I would like to discuss why this initial discovery of boundary expansion is important to me. First, just doing the project was practice at researching. Perhaps my interpretation of the articles and my understanding of the eye are wrong. If I am wrong, then I should correct my information after the grading period. Therefore, the assignment serves the purpose of stimulating critical thinking. Second, on a larger level I think this kind of research may help further the understanding of clinical research. Third, I also think this kind of research may be useful on a practical level; at places such as schools where science teachers can understand the memory better and use that understanding to improve teaching methods.


                                                                                                     
References

Gottesman V. C., & Intraub H. (1999). Wide angle memories of close up scenes: A
demonstration of boundary extension. Behavior Research Methods, Instruments, &
Computers, 31(1), 86-93.

Mullary L. S., Intraub H., & Maguire A. E (2012). Attenuated Boundary Expansion Produces a
Paradoxical Memory Advantage in Amnesiac Patients. Current Biology 22, 261-268.



Quote:

Several articles related to the topic of Boundary extension:

1.
Neuron: Beyond the edges of a view: boundary extension in human scene-selective visual cortex.
Soojin Park, Helen Intraub, Do-Joon Yi, David Widders, and Marvin M. Chun.

2.
Cortex: Research report: The hippocampus extrapolates beyond the view in scenes: An fMRI study of boundary extension.
Martin J. Chadwick, Sine´ad L. Mullally, and Eleanor A. Maguire

3.
Current Biology: Article: Attenuated Boundary Extension Produces a Paradoxical Memory Advantage in Amnesic Patients.
Sine´ad L. Mullally, Helene Intraub, and Eleanor A. Maguire

4.
Gottesman V. C., & Intraub H. (1999). Wide angle memories of close up scenes: A
demonstration of boundary extension. Behavior Research Methods, Instruments, &
Computers, 31(1), 86-93.






Quote:

On memory and how it relates to boundary extension.









Quote:

A lecture on visual perception. Similar to the one I had in class.








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Currently the Korean Language thread is analyzing a Korean Pop song. The song and lyrics can be found on the following page.

http://www.shroomery.org/forums/showflat.php/Number/20660261/fpart/9/vc/1#20660261


Edited by XUL (11/14/14 02:42 PM)


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OfflineXUL
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Re: Perception and Boundary Extension [Re: XUL]
    #20567423 - 09/14/14 05:27 PM (9 years, 4 months ago)

Boundary Extension

“a tendency to remember seeing a greater expanse of a scene than was shown in a photograph.”

Carmela V. Gottesman and Helene Intraub (1999)




Cause?

• exists because of the viewer’s expectations of the photograph.

• memory plays a role on boundary expansion is important because it further illustrates that prior knowledge (top down processing) is an important part of perception




Etiology

• clinical patients with damage to the hippocampus are not as susceptible to boundary extension

• impaired memory

• patients with hippocampal damage do not use as much prior knowledge as a healthy adult




Importance

• visual acuity is most accurate when the stimulus reaches the cone rich fovea

• In contrast, light that does not directly hit the fovea becomes more peripheral

• because our peripheral area of the eye lacks acuity, we compensate for this by creating perceptual schemas

• perceptual schemas are our prior knowledge

• boundary extension is an example of top down processing. Using prior knowledge in order to create full perceptions.



References

Gottesman V. C., & Intraub H. (1999). Wide angle memories of close up scenes: A
demonstration of boundary extension. Behavior Research Methods, Instruments, &
Computers, 31(1), 86-93.

Mullary L. S., Intraub H., & Maguire A. E (2012). Attenuated Boundary Expansion Produces a
Paradoxical Memory Advantage in Amnesiac Patients. Current Biology 22, 261-268.


--------------------
Currently the Korean Language thread is analyzing a Korean Pop song. The song and lyrics can be found on the following page.

http://www.shroomery.org/forums/showflat.php/Number/20660261/fpart/9/vc/1#20660261


Edited by XUL (11/12/14 07:37 PM)


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InvisibleStaplerhead
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Registered: 12/02/11
Posts: 671
Re: Perception and Boundary Extension [Re: XUL]
    #20628063 - 09/27/14 09:34 PM (9 years, 4 months ago)

Interesting. Will thoroughly read when I have time.


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