HONORS RESEARCH II
HONORS RESEARCH II PSY 379H
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Date Created: 09/07/15
Jennifer Sandler Literature Review Visual Search and Gender Differences The existence of gender differences in visual search tasks is a topic that is overlooked in present psychological research While much is known about various gender differences in cognitive ability it seems that nothing is currently known about whether or not gender difference exist in visual search tasks Visual search tasks are simply those in which someone looks for something Real world applications include searching for information on an xray for the correct key on a keyboard looking for a car in a parking lot or a specific word in text Palmer 1995 An understanding of whether gender differences in visual search exist in the laboratory could have useful applications to more naturalistic real world situations In a typical visual search experiment the participant is presented with a display that contains a number of items On each trial a decision must be made as to whether or not a specific target item is present among the distractor items The set size or number of items can vary from trial to trial The accuracy of the response as well at the reaction time the amount of time required to make a targetpresen or targetabsen response are recorded and analyzed Visual search experiments can usually be put into one of two categories parallel searches and serial searches A parallel search is one in which all items in the display can be processed in one step Serial searches are ones in which attention is moved from item to item until the target is found Wolfe 1998b Visual search tasks can additionally be divided into six categories feature searches hard feature searches conjunction searches withindimension conjunction searches spatial configuration searches and other searches Wolfe 1998b Feature searches are those in Jennifer Sandler which the target is de ned by a unique single feature typically either color or orientation Hard feature searches are characterized by the target having a unique orientation but the search is theoretically more difficult Combinations of two different features such as color and orientation or curvature and size define the targets of a conjunction search A withindimension conjunction search consists of targets with a conjunction of two instances of the same type of feature for example colorbycolor conjunction searches Spatial configuration searches are those in which the target is not defined by simple features but rather by the arrangement of line segments Wolfe 1998b These experiments can be valuable because performance on visual search tasks varies with the type of stimuli used While it is the case that not all feature attributes can be characterized in terms of basic features there is a consensus about a small number of features that can be classified in this manner Wolfe 1998a Perhaps the most straightforward case is color A color difference between the target and distractors is one of the most e cient ways to make the target pop ou from the rest of the display Wolfe 1998a However as the color differences shrinks the search becomes more ine cient Efficiency is a descriptive term used to differentiate between searches where the target pops out from the display and searches where the number of distractors makes it more difficult to locate the target Hence a more inefficient search is characterized by larger reaction times It has been found that if there is more than one distractor color efficient search is possible but constraints do exist Duncan 1988 A number of experiments have shown that search for a uniquely colored target among up to nine distractor colors can in fact be efficient but only if the distractors are widely separated in color space D Zmura 1991 Thus if more similar colors are used the search is Jennifer Sandler inefficient if the distractor colors are close to the target color in color space D Zmura 1991 has found that efficient search can be achieved if the target and distractor colors lie on different sides when a line is drawn through them in color space This concept called linear separability holds only if the color differences are not too large Research done by Treisman and Gormican 1988 indicates that it is easier to find a deviation from a prototypical color than to nd the prototypical color itself This situation describes an instance of a search asymmetry or a situation in which it is easier to find A among B than it is to find B among A Thus Treisman s work has shown that some targets are easy to find if and only if they contain some unique basic feature information Another basic feature of visual search is orientation If the distractors are of different orientations search is more inefficient Wolfe 1998a Once again with orientation as well the difficulty of the task can largely be explained by the similarity of the target and the distractors and also the similarities between different types of distractors Curvature yet another basic feature has also been found to adhere to the above rule For example when the target is straight and the detractors are curved the result is a less efficient search task Wolfe 1998a The fact that the presence of curvature is easier to detect than its absence provides evidence of another search asymmetry Size is another basic feature that is commonly examined in visual search Three aspects of size are considered in visual search experiments First a target can differ in overall size in relation to other items for example searching for a small target among larger distractors Secondly it is possible for a target item to have the same overall dimensions as other items but still differ spatial frequency Items can also contain Jennifer Sandler different information at different scales An example of this is Navon s stimuli in which a global letter is made up of a series of a smaller local letter Results of several different experiments of this type have led to the conclusion that if the size difference is great enough a target can be efficiently found among distractors of a different size Wolfe 1998a Additionally Treisman has found the existence of another asymmetry that occurs when the target and distractors differ in size She found proof that it is harder to find a small target among large distractors than it is to find big among small Treisman amp Gormican 1988 Shape as a basic feature is best discussed in terms of line termination Treisman and Gormican 1988 have found that gaps or line terminations are more easily detected In their experiment they found an asymmetry in which it was easier to find the letter C among distractor O s Closure the opposite of line termination is important in the preattentive processing of form The preattentive processing of any feature can be used to guide the succeeding deployment of attention and thus preattentive information is commonly used in Visual search tasks Preattentive processing directs attention to locations of interesting objects in the Visual field There are two ways in which preattentive processing is used in guiding attention from object to object bottomup and topdown Wolfe 1998a Bottomup refers to stimulus driven control of the preattentive process This occurs in situations where attention is attracted to an unusual item or when an item pops ou Topdown processing refers to userdriven control of preattentive processes such as consciously directing attention from one item to another in search of a particular feature or target Wolfe 1998a Jennifer Sandler While much is known about visual search the existence of gender differences within in it is a topic widely ignored in the current literature Nonetheless it is a topic worth examining Although this particular topic is largely ignored much of the research examining gender differences in cognitive abilities seems applicable to visual search To begin most of the gender differences that have been discovered have an evolutionary basis tracing back to the emergence of a division of labor with ancestral females doing the gathering and ancestral males the hunting Joseph 2000 It is reasonable to assume that sex differences in labor in turn promoted innate sex differences in visualspatial skills A successful hunter must have been capable of analyzing the spatial coordinates that would link him to prey and also must have had the ability to aim and throw a spear Joseph 2000 As hunting required good visualspatial and motor skills it is not surprising that modern males still outperform females in tasks designed to test these skills There is an extensive amount of research that offers support for these gender differences Research has shown that females typically excel at tasks requiring perceptual speed identifying matching items verbal and ideational uency precision manual tasks mathematical calculations and at determining whether an object has been displaced from a series of objects Kimura 1993 Males on the other hand perform better than females on various spatial tasks including mental rotation Additionally men outperform women on disembedding tests mathematical reasoning and are more accurate in targetdirected motor skills Kimura 1993 There are also gender differences in navigation strategies where females have a greater tendency to use landmarks as a strategy to orient themselves while males more likely rely on spatial cues Jennifer Sandler Halpem ampLaMay 2000 Differing patterns of ability between the sexes most likely re ect different hormonal in uences on their brains during development Kimura 1993 Is it then possible that the same androgens and estrogens that establish sexual differentiation including sexual differentiation in cognitive abilities could also establish gender differences in how the visual field is searched The gender differences that have surfaced in these tests of cognitive ability adhere to an evolutionary model For example it is possible that females having better memory for spatial locations re ects the ancestral female role of gatherer As gatherers females must have needed good memory for the location of plants The visual search skills required for hunting should have differed than those required for gathering If that is the case it is possible that an evolved gender difference in visual search skills could be prevalent in modern humans From what is known about performance on visual search tasks together with gender differences in cognitive ability it is reasonable to consider whether or not a gender difference could emerge depending on the nature of the search task Determining whether an object has been displaced from a series of objects a task at which females excel seems to almost be the reverse of the problem presented in visual search tasks The latter requires identifying the presence of an item while the former requires identifying not only that an item is absent but specifically which item Thus it is also a possibility that in regard to the search asymmetries discussed earlier one sex might actually be better at finding B among A than A among B Additionally many visual search tasks require spatial rotation skills and it seems that since males perform better on tests involving mentally rotating objects there may Jennifer Sandler also be a sex difference in these types of tasks If a gender difference were to appear it would be expected to specifically emerge in spatial con guration searches and those involving orientation It is also important to note that the more inefficient the search task the more likely a gender difference is to emerge While it is plausible that there are differences it is less likely for them to occur in search tasks that only involve basic features Thus the more processes involved in discriminating between items the more likely it is that there will be a gender difference somewhere along the line Jennifer Sandler References D Zmura M 1991 Color in visual search Vision Research 316 951966 Halpem DF and LaMay ML 2000 The smarter sex A critical review of sex differences in intelligence Educational Psychology Review 122 229246 Joseph R 2000 The evolution of sex differences in language sexuality and visualspatial skills Archives of Sexual Behavior 291 3566 Kimura D 1993 Sex differences in the brain Scientific American 7989 Palmer John 1995 Attention in visual search Distinguishing four causes of a setsize effect Psychological Science 414 118123 Treisman Anne 1986 Features and objects in visual processing Scientific American 2555 114125 Treisman A and Gormican S 1988 Feature analysis in early vision Evidence from search asymmetries Psychological Review 95 1548 Wolfe Jeremy 1998a Visual search Attention 1373 Wolfe Jeremy 1998b What can one million trials tell us about visual search Psychological Science 911 3339 Jennifer Sandler
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