Theories of Visual Search
A standard theory of visual search tasks assumes that when a person searches for a target in an array of other items, memory is used in locating the target. The following analysis of three articles shows that there is both strong support for this highly respected theory and evidence that this theory may have some flaws in reasoning.
In the article "Features and Objects in Visual Processing," Anne Treisman states that there are two theoretical levels of visual processing. In the first level of visual processing, certain components of visual information are processed instantly and unconsciously. A person does not have to concentrate on individual parts of the scene. This stage of processing is called the preattentive stage. During the preattentive stage, the light received by the visual receptors is translated in to the lines, curves, colors and textures of the objects. Within the brain, there are two distinct visual areas that specialize in different areas of processing. The first area processes lines, curves, color, and texture and other areas deal with movement. After this initial processing occurs, another area of the brain processes the more complex and distinct qualities of a scene. Then, all of the components of the objects in the scene are recombined into whole objects. In order to support the preattentive stage of visual processing, Treisman devises that parts of objects that belong to the same object share similar attributes. Attributes such as color, continuity of lines and curves that define the boundaries between objects. She uses an experiment to determine which properties of a visual stimulus make its boundaries stand out from other similar objects. The properties of an object that make it stand out are used by the visual processing system in distinguishing the object from ground. In actuality, boundaries are conspicuous between components that are distinctive in basic properties such as color, brightness and line orientation but not in the way their properties are connected or grouped. In an experiment showing evidence of this principle, subjects are shown a picture in which a region of T’s easily distinguishes itself from an area of slanted T’s but not from a region of backwards L’s that are constructed of the same geons as the T’s. This illustrates that line orientations are important features in the preattentive stage of visual processing and that the specific configurations or conjunctions of lines are not.
The ultimate goal for a system of visual perception is representing visual scenes. It is generally assumed that this requires an initial ‘break-down’ of complex visual stimuli into some kind of “discrete subunits” (De Valois & De Valois, 1980, p.316) which can then be passed on and further processed by the brain. The task thus arises of identifying these subunits as well as the means by which the visual system interprets and processes sensory input. An approach to visual scene analysis that prevailed for many years was that of individual cortical cells being ‘feature detectors’ with particular response-criteria. Though not self-proclaimed, Hubel and Wiesel’s theory of a hierarchical visual system employs a form of such feature detectors. I will here discuss: the origins of the feature detection theory; Hubel and Wiesel’s hierarchical theory of visual perception; criticism of the hierarchical nature of the theory; an alternative theory of receptive-field cells as spatial frequency detectors; and the possibility of reconciling these two theories with reference to parallel processing.
Another speaker, Margaret Livingstone delves into the visual aspect of our senses. Livingstone mentions how artists recognize things about vision that neuroscientists are not privy to until years later. Livingstone discussed the differentiation between color and lightness, and how the two contribute differently to a work of art. Color is thought of as “comparing activity” whereas light is thought of as “summing them.” Livingstone indicates that the visual system is subdivided into a ventral system and a dorsal system. The ventral system is responsible for object recognition, face recognition, and color. The dorsal system is responsible for navigating through the environment, special organization, and emotional recognition. The ability for humans to see distance and depth is carried via our colorblind part of our visual system. As a result, Livingstone concludes that one cannot see depth and shading unless the luminance is right to convey three-dimensional.
One of the most common American proverbs is the expression to “never judge a book by its cover”. This saying, used for more than just books, is commonly used to express that what is on the appearance of something might not always show that things true nature or content. Even so people will often forget this fact and rely on their own perception. So what does this say about perception? To Victor Hugo author of the novel Les Misérables this would probable show that human perception is flawed and that people trust it more than they should. In Victor Hugo’s novel Les Misérables he suggests that by following only our perception will not always lead to the truth, with the characters of Thénardier, Jean Valjean, and Inspecter Javert.
One wonders what takes place in the brain to cause such phenomenal differences in perception. The cause is unknown for certain, like many things in the realm of science it has not been researched nearly enough, but there are some indications.
The ‘where visual pathway’ is concerned with constructing three dimensional representations of the environment and helps our brain to navigate where things are, independently of what they are, in space in relation to itself (Mishkin & Ungerleider & Macko, 1983).... ... middle of paper ... ... The 'Standard' of the 'Standard'.
Processing capacity is a very broad and flexible category according to many researchers. In fact, the quote above mentioned suggests that we often fail to notice things that happen just in front of us (unexpected events that are often salient) either because we were completely absorbed by something else or because we had so many things to do at the same time that we couldn’t pay attention to it. We have all at least once failed to see a friend who was waving at us while eating in the cafeteria or walking in a crowded street. The primary question that we should ask ourselves is: how many things can we attend at the same time? The truth is that we didn’t perceive this friend because of a phenomenon called “inattentional blindness”. The problem is that the richness of our visual experience leads us to believe that our visual representation will include and preserve the same amount of detail (Levin et al 2000). In this paper we’ll see the different theories of inattentional blindness, and the classical theories demonstrating this paradigm.
Mervis, C. B. & Rosch, E. (1981). Categorization of natural objects. Annual Review of Psychology, 32, 89-115.
The Effects of Levels of Processing on Memory PB1: Identify the aim of the research and state the experimental/alternative hypothesis/es. (credited in the report mark scheme) To show how different levels of processing affects the memory. “People who process information deeply (i.e. semantic processing) tend to remember more than those who process information shallowly (i.e. visual processing). ” PB2: Explain why a directional or non-directional experimental/alternative hypothesis/es has been selected. (I mark) I have used a directional experimental hypothesis because past research, such as that by Craik and Tulving (1975) has proved this. PB3:
Sajda P. & Finkle, L.H. (1995) Intermediate Visual Representations and the Construction of Surface Perception. Journal of Cognitive Neuroscience, 7, 267-291.
In response, they proposed that perception is based on the organization of stimuli into holistic and meaningful forms. They are well-known for the phrase "the whole is different than the sum of its parts. " They proposed several "laws" (really heuristics or "rules of thumb") that are referred to as the Gestalt laws of perceptual organization. These are discussed in the module later on.
Williams, Y 2003, ‘Retrieval Cues: Definition, Examples & Quiz’ Education portal, Veiwed on the 22nd of march 2014
Our five senses –sight, hearing, smell, taste and touch help the ways in which we perceive the world around us. And while they seem to work independently at time they can effect each other and the way we comprehend something. Seeing something pretty, touching something soft, eating something cold and smelling something rotten are the sense we use to connect with the world around us and will all effect how we move forward in that situation. When you look at the top picture say the color of the word not the word itself. It is harder than it seems and takes a little practice to do it efficiently. It is because we see the spelling we were taught not the color it was written in. It is hard to process it the other way, but not impossible. Take the bottom picture for another example is this a
Visual Discrimination is “using the sense of sight to notice and compare the features of different items to distinguish one item from another” (NCLD Editorial Team, 2014) http://www.ncld.o...
Prior knowledge plays a pivotal role in every aspect of human life. Knowledge can be stored in various formats like images, features, statistical patterns, all these formats help in making sense of the environment. Using prior knowledge humans can perform various activities including, but not limited to: focusing attention, organizing information in to groups, categorizing objects around, hypothesizing, understanding language, and generating inferences(Smith & Kosslyn, 2007). Processing of information is influenced by prior knowledge during the top down processing. Once signal has been detected by the biological visual system, we try to infer meaning using the prior related knowledge which has been stored in the long term memory based on category, association and similarity in features and statistical patterns(Wickens, Lee, Liu, & Becker, 2004). Prior knowledge has no boundaries and it keeps on changing based on experience with the environment making it easier for us humans to understand our surrounding better and quicker as time passes.
There are many different Visual Perception principles in perception. The main principles are Gestalt. Gestalt is a German word meaning 'form' or 'shape'. Gestalt psychologists formulated a series of principles that describe how t...